The Galaxy-Halo Connection Over The Last 13.3 Gyrs [GA]

http://arxiv.org/abs/1703.04542


We present new determinations of the stellar-to-halo mass relation (SHMR) at $z=0-10$ that match the evolution of the galaxy stellar mass function, the SFR$-M_*$ relation,and the cosmic star formation rate. We utilize a compilation of 40 observational studies from the literature and correct them for potential biases. Using our robust determinations of halo mass assembly and the SHMR, we infer star formation histories, merger rates, and structural properties for average galaxies, combining star-forming and quenched galaxies. Our main findings: (1) The halo mass $M_{50}$ above which 50\% of galaxies are quenched coincides with sSFR/sMAR$\sim1$, where sMAR is the specific halo mass accretion rate. (2) $M_{50}$ increases with redshift, presumably due to cold streams being more efficient at high redshift while virial shocks and AGN feedback become more relevant at lower redshifts. (3) The ratio sSFR/sMAR has a peak value, which occurs around $M_{\rm vir}\sim2\times10^{11}M_{\odot}$. (4) The stellar mass density within 1 kpc, $\Sigma_1$, is a good indicator of the galactic global sSFR. (5) Galaxies are statistically quenched after they reach a maximum in $\Sigma_1$, consistent with theoretical expectations of the gas compaction model; this maximum depends on redshift. (6) In-situ star formation is responsible for most galactic stellar mass growth, especially for lower-mass galaxies. (7) Galaxies grow inside out. The marked change in the slope of the size–mass relation when galaxies became quenched, from $d\log R_{\rm eff}/d\log M_*\sim0.35$ to $\sim2.5$, could be the result of dry minor mergers.

Read this paper on arXiv…

A. Rodriguez-Puebla, J. Primack, V. Avila-Reese, et. al.
Thu, 16 Mar 17
50/92

Comments: 41 pages, 31 Figures. Submitted to MNRAS. The results presented in this paper are available at this https URL

A Possible Solution for the $M/L-\mathrm{[Fe/H]}$ Relation of Globular Clusters in M31. II. the Age-Metallicity Relation [GA]

http://arxiv.org/abs/1703.04635


This is the second of a series of papers in which we present a new solution to reconcile the prediction of single stellar population (SSP) models with the observed stellar mass-to-light ($M/L$) ratios of globular clusters (GCs) in M31 and its trend with respect to $\mathrm{[Fe/H]}$. In the present work our focus is on the empirical relation between age and metallicity for GCs and its effect on the $M/L$ ratio. Assuming that there is an anti-correlation between the age of M31 GCs and their metallicity, we evolve dynamical SSP models of GCs to establish a relation between the $M/L$ ratio (in the $V$ and $K$ band) and metallicity. We then demonstrate that the established $M/L-\mathrm{[Fe/H]}$ relation is in perfect agreement with that of M31 GCs. In our models we consider both the canonical initial mass function (IMF) and the top-heavy IMF depending on cluster birth density and metallicity as derived independently from Galactic GCs and ultra-compact dwarf galaxies by Marks et al. Our results signify that the combination of the density- and metallicity-dependent top-heavy IMF, the anti-correlation between age and metallicity, stellar evolution and standard dynamical evolution yields the best possible agreement with the observed trend of $M/L-\mathrm{[Fe/H]}$ for M31 GCs.

Read this paper on arXiv…

H. Haghi, P. Khalaj, A. Zonoozi, et. al.
Thu, 16 Mar 17
51/92

Comments: 8 pages, 4 figures, 1 table. Accepted for publication in ApJ

Dark Matter Constraints from a Joint Analysis of Dwarf Spheroidal Galaxy Observations with VERITAS [HEAP]

http://arxiv.org/abs/1703.04937


We present constraints on the annihilation cross section of WIMP dark matter based on the joint statistical analysis of four dwarf galaxies with VERITAS. These results are derived from an optimized photon weighting statistical technique that improves on standard imaging atmospheric Cherenkov telescope (IACT) analyses by utilizing the spectral and spatial properties of individual photon events. We report on the results of $\sim$230 hours of observations of five dwarf galaxies and the joint statistical analysis of four of the dwarf galaxies. We find no evidence of gamma-ray emission from any individual dwarf nor in the joint analysis. The derived upper limit on the dark matter annihilation cross section from the joint analysis is $1.35\times 10^{-23} {\mathrm{ cm^3s^{-1}}}$ at 1 TeV for the bottom quark ($b\bar{b}$) final state, $2.85\times 10^{-24}{\mathrm{ cm^3s^{-1}}}$ at 1 TeV for the tau lepton ($\tau^{+}\tau^{-}$) final state and $1.32\times 10^{-25}{\mathrm{ cm^3s^{-1}}}$ at 1 TeV for the gauge boson ($\gamma\gamma$) final state.

Read this paper on arXiv…

VERITAS. Collaboration, S. Archambault, A. Archer, et. al.
Thu, 16 Mar 17
52/92

Comments: 14 pages, 9 figures, accepted for publication in PRD

Gravitational Waves from Core-Collapse Supernovae [HEAP]

http://arxiv.org/abs/1703.04633


Gravitational waves are a potential direct probe for the multi-dimensional flow during the first second of core-collapse supernova explosions. Here we outline the structure of the predicted gravitational wave signal from neutrino-driven supernovae of non-rotating progenitors from recent 2D and 3D simulations. We sketch some quantitative dependencies that govern the amplitudes of this signal and its evolution in the time-frequency domain.

Read this paper on arXiv…

B. Muller
Thu, 16 Mar 17
53/92

Comments: 4 pages, invited contribution prepared for the minisymposium “Gravitational Waves: Sources and Detection” at the 13th International Conference on Mathematical and Numerical Aspects of Wave Propagation, Minnesota, 2017

The Search for Multiple Populations in Magellanic Cloud Clusters III: No evidence for Multiple Populations in the SMC cluster NGC 419 [GA]

http://arxiv.org/abs/1703.04631


We present the third paper about our ongoing HST survey for the search for multiple stellar populations (MPs) within Magellanic Cloud clusters. We report here the analysis of NGC 419, a $\sim 1.5$ Gyr old, massive ($\gtrsim 2 \times 10^5 \, {\rm M_{\odot}}$) star cluster in the Small Magellanic Cloud (SMC). By comparing our photometric data with stellar isochrones, we set a limit on [N/Fe] enhancement of $\lesssim$+0.5 dex and hence we find that no MPs are detected in this cluster. This is surprising because, in the first two papers of this series, we found evidence for MPs in 4 other SMC clusters (NGC 121; Lindsay 1, NGC 339, NGC 416), aged from 6 Gyr up to $\sim 10-11$ Gyr. This finding raises the question whether age could play a major role in the MPs phenomenon. Additionally, our results appear to exclude mass or environment as the only key factors regulating the existence of a chemical enrichment, since all clusters studied so far in this survey are equally massive ($\sim 1-2 \times 10^5 \, {\rm M_{\odot}}$) and no particular patterns are found when looking at their spatial distribution in the SMC.

Read this paper on arXiv…

S. Martocchia, N. Bastian, C. Usher, et. al.
Thu, 16 Mar 17
54/92

Comments: MNRAS, accepted. 9 pages, 7 figures

Strongly Coupled Dark Energy with Warm dark matter vs. LCDM [CEA]

http://arxiv.org/abs/1703.05139


Cosmologies including strongly Coupled (SC) Dark Energy (DE) and Warm dark matter (SCDEW) are based on a conformally invariant (CI) attractor solution modifying the early radiative expansion. Then, aside of radiation, a kinetic field $\Phi$ and a DM component account for a stationary fraction, $\sim 1\, \%$, of the total energy. SCDEW models alleviate conceptual problem of LCDM, while recovering its results, and even easing some LCDM problems, below the average galaxy scale. The CI expansion begins at the inflation end, when $\Phi$ (future DE) possibly plays a role in reheating, and ends at the Higgs’ scale. Afterwards, a number of viable options is open, allowing for the transition from the CI expansion to the present Universe. In this paper: (i) We show how the attractor is recovered when the spin degrees of freedom decreases. (ii) We perform a detailed comparison of CMB anisotropy and polarization spectra for SCDEW and LCDM, including tensor components, finding negligible discrepancies. (iii) Linear spectra exhibit a greater parameter dependence at large $k$’s, but are still consistent with data for suitable parameter choices. (iv) We also compare previous simulation results with fresh data on galaxy concentration. Finally, (v) we outline numerical difficulties at high $k$. This motivates a second related paper, where such problems are treated in a quantitative way.

Read this paper on arXiv…

S. Bonometto, M. Mezzetti and R. Mainini
Thu, 16 Mar 17
55/92

Comments: 23 pages, 10 figures

An Investigation of the Rotational Properties of Magnetic Chemically Peculiar Stars [SSA]

http://arxiv.org/abs/1703.05218


The magnetic chemically peculiar (mCP) stars of the upper main sequence exhibit strong, globally-organised magnetic fields which are inclined to the rotational axis and facilitate the development of surface abundance inhomogeneities resulting in photometric and spectroscopic variability. Therefore, mCP stars are perfectly suited for a direct measurement of the rotational period without the need for any additional calibrations. We have investigated the rotational properties of mCP stars based on an unprecedentedly large sample consisting of more than 500 objects with known rotational periods. Using precise parallaxes from the Hipparcos and Gaia satellite missions, well-established photometric calibrations and state-of-the-art evolutionary models, we have determined the location of our sample stars in the Hertzsprung-Russell diagram and derived astrophysical parameters such as stellar masses, effective temperature, radii, inclinations and critical rotational velocities. We have confirmed the conservation of angular momentum during the main sequence evolution; no signs of additional magnetic braking were found. The inclination angles of the rotational axes are randomly distributed, although an apparent excess of fast rotators with comparable inclination angles has been observed. We have found a rotation rate of $\upsilon/\upsilon_{\rm crit} \geq 0.5$ for several stars, whose characteristics cannot be explained by current models. For the first time, we have derived the relationship between mass and rotation rate of mCP stars, and provide an analysis that links mass and rotation with magnetic field strength. Our sample is unique and offers crucial input for forthcoming evolutionary models that include the effects of magnetic fields for upper main sequence stars.

Read this paper on arXiv…

M. Netopil, E. Paunzen, S. Hummerich, et. al.
Thu, 16 Mar 17
56/92

Comments: 13 pages, 9 figures, accepted for publication in MNRAS

Detection of faint broad emission lines in type 2 AGN: II. On the measurement of the BH mass of type 2 AGN and the unified model [GA]

http://arxiv.org/abs/1703.05167


We report the virial measurements of the BH mass of a sample of 17 type 2 AGN, drawn from the Swift/BAT 70-month 14-195 keV hard X-ray catalogue, where a faint BLR component has been measured via deep NIR (0.8-2.5 $\mu$m) spectroscopy. We compared the type 2 AGN with a control sample of 33 type 1 AGN. We find that the type 2 AGN BH masses span the 5$<$ log(M$_{BH}$ /M$_{\odot}$) $< $7.5 range, with an average log(M$_{BH}$/M$_{\odot}$) = 6.7, which is $\sim$ 0.8 dex smaller than found for type 1 AGN. If type 1 and type 2 AGN of the same X-ray luminosity log($L_{14-195}$/erg s$^{-1}$) $\sim$ 43.5 are compared, type 2 AGN have 0.5 dex smaller BH masses than type 1 AGN. Although based on few tens of objects, this result disagrees with the standard AGN unification scenarios in which type 1 and type 2 AGN are the same objects observed along different viewing angles with respect to a toroidal absorbing material.

Read this paper on arXiv…

F. Onori, F. Ricci, F. Franca, et. al.
Thu, 16 Mar 17
57/92

Comments: 6 pages, 5 figures, accepted for publication in MNRAS

WISDOM Project – II: Molecular gas measurement of the supermassive black hole mass in NGC4697 [GA]

http://arxiv.org/abs/1703.05248


As part of the mm-Wave Interferometric Survey of Dark Object Masses (WISDOM) project, we present an estimate of the mass of the supermassive black hole (SMBH) in the nearby fast-rotating early-type galaxy NGC4697. This estimate is based on Atacama Large Millimeter/submillimeter Array (ALMA) cycle-3 observations of the 12CO(2-1) emission line with a linear resolution of 29 pc (0.53″). We find that NGC4697 hosts a small relaxed central molecular gas disc with a mass of 1.6×10^7 Msun, co-spatial with the obscuring dust disc visible in optical Hubble Space Telescope (HST) imaging. We also resolve thermal 1mm continuum emission from the dust in this disc. NGC4697 is found to have a very low molecular gas velocity dispersion, $\sigma_{gas}=1.65^{+0.68}_{-0.65}$ km/s. This seems to be partially because the giant molecular cloud mass function is not fully sampled, but other mechanisms such as chemical differentiation in a hard radiation field or morphological quenching also seem to be required. We detect a Keplerian increase of the rotation of the molecular gas in the very centre of NGC4697, and use forward modelling of the ALMA data cube in a Bayesian framework with the KINematic Molecular Simulation (KinMS) code to estimate a SMBH mass of ($1.3_{-0.17}^{+0.18})\times10^8$ Msun and an i-band mass-to-light ratio of $2.14_{-0.05}^{+0.04}$ Msun/Lsun (at the 99% confidence level). Our estimate of the SMBH mass is entirely consistent with previous measurements from stellar kinematics. This increases confidence in the growing number of SMBH mass estimates being obtained in the ALMA era.

Read this paper on arXiv…

T. Davis, M. Bureau, K. Onishi, et. al.
Thu, 16 Mar 17
58/92

Comments: 16 pages, 11 figures, accepted to MNRAS

Modelling Jets, Tori and Flares in Pulsar Wind Nebulae [HEAP]

http://arxiv.org/abs/1703.05184


In this contribution we review the recent progress in the modeling of Pulsar Wind Nebulae (PWN). We start with a brief overview of the relevant physical processes in the magnetosphere, the wind-zone and the inflated nebula bubble. Radiative signatures and particle transport processes obtained from 3D simulations of PWN are discussed in the context of optical and X-ray observations. We then proceed to consider particle acceleration in PWN and elaborate on what can be learned about the particle acceleration from the dynamical structures called “wisps” observed in the Crab nebula. We also discuss recent observational and theoretical results of gamma-ray flares and the inner knot of the Crab nebula, which had been proposed as the emission site of the flares. We extend the discussion to GeV flares from binary systems in which the pulsar wind interacts with the stellar wind from a companion star. The chapter concludes with a discussion of solved and unsolved problems posed by PWN.

Read this paper on arXiv…

O. Porth, R. Buehler, B. Olmi, et. al.
Thu, 16 Mar 17
59/92

Comments: To appear in “Jets and Winds in Pulsar Wind Nebulae, Gamma-ray Bursts and Blazars: Physics of Extreme Energy Release” of the Space Science Reviews series. The final publication is available at Springer via this http URL

Characterizing a CCD detector for astronomical purposes: OAUNI Project [IMA]

http://arxiv.org/abs/1703.04836


This work verifies the instrumental characteristics of the CCD detector which is part of the UNI astronomical observatory. We measured the linearity of the CCD detector of the SBIG STXL6303E camera, along with the associated gain and readout noise. The linear response to the incident light of the detector is extremely linear (R2 =99.99%), its effective gain is 1.65 +/- 0.01 e-/ADU and its readout noise is 12.2 e-. These values are in agreement with the manufacturer. We confirm that this detector is extremely precise to make measurements for astronomical purposes.

Read this paper on arXiv…

A. Pereyra, M. Zevallos, J. Ricra, et. al.
Thu, 16 Mar 17
60/92

Comments: 6 pages, 8 figures, Published by TECNIA (UNI)

On the post-Keplerian corrections to the orbital periods of a two-body system and their application to the Galactic Center [GA]

http://arxiv.org/abs/1703.04947


Detailed numerical analyses of the orbital motion of a test particle around a spinning primary are performed. They aim to investigate the possibility of using the post-Keplerian (pK) corrections to the orbiter’s periods (draconitic, anomalistic and sidereal) as a further opportunity to perform new tests of post-Newtonian (pN) gravity. As a specific scenario, the S-stars orbiting the Massive Black Hole (MBH) supposedly lurking in Sgr A$^\ast$ at the center of the Galaxy is adopted. We, first, study the effects of the pK Schwarzchild, Lense-Thirring and quadrupole moment accelerations experienced by a target star for various possible initial orbital configurations. It turns out that the results of the numerical simulations are consistent with the analytical ones in the small eccentricity approximation for which almost all the latter ones were derived. For highly elliptical orbits, the size of all the three pK corrections considered turn out to increase remarkably. The periods of the observed S2 and S0-102 stars as functions of the MBH’s spin axis orientation are considered as well. The pK accelerations considered lead to corrections of the orbital periods of the order of 1-100d (Schwarzschild), 0.1-10h (Lense-Thirring) and 1-10^3s (quadrupole) for a target star with a=300-800~AU and e ~ 0.8, which could be possibly measurable by the future facilities.

Read this paper on arXiv…

L. Iorio and F. Zhang
Thu, 16 Mar 17
61/92

Comments: Accepted for publication in ApJ

ZFIRE: Using h$α$ equivalent widths to investigate the in situ initial mass function at z~2 [GA]

http://arxiv.org/abs/1703.04536


We use the ZFIRE survey (this http URL) to investigate the high mass slope of the initial mass function (IMF) for a mass-complete (log10(M$_*$/M$_\odot$)~9.3) sample of 102 star-forming galaxies at z~2 using their H{\alpha} equivalent widths (H{\alpha}-EW) and rest-frame optical colours. We compare dust-corrected H{\alpha}-EW distributions with predictions of star-formation histories (SFH) from PEGASE.2 and Starburst99 synthetic stellar population models. We find an excess of high H{\alpha}-EW galaxies that are up to 0.3–0.5 dex above the model-predicted Salpeter IMF locus and the H{\alpha}-EW distribution is much broader (10–500 \AA) than can easily be explained by a simple monotonic SFH with a standard Salpeter-slope IMF. Though this discrepancy is somewhat alleviated when it is assumed that there is no relative attenuation difference between stars and nebular lines, the result is robust against observational biases, and no single IMF (i.e. non-Salpeter slope) can reproduce the data. We show using both spectral stacking and Monte Carlo simulations that starbursts cannot explain the EW distribution. We investigate other physical mechanisms including models with variations in stellar rotation, binary star evolution, metallicity, and the IMF upper-mass cutoff. IMF variations and/or highly rotating extreme metal poor stars (Z~0.1Z$_\odot$) with binary interactions are the most plausible explanations for our data. If the IMF varies, then the highest H{\alpha}-EWs would require very shallow slopes ({\Gamma}>-1.0) with no one slope able to reproduce the data. Thus, the IMF would have to vary stochastically. We conclude that the stellar populations at z~2 show distinct differences from local populations and there is no simple physical model to explain the large variation in H{\alpha}-EWs at z~2.

Read this paper on arXiv…

T. Nanayakkara, K. Glazebrook, G. Kacprzak, et. al.
Thu, 16 Mar 17
62/92

Comments: Accepted to MNRAS. 43 pages, 27 Figures. Survey website: this http URL

Baryogenesis at a Lepton-Number-Breaking Phase Transition [CL]

http://arxiv.org/abs/1703.04902


We study a scenario in which the baryon asymmetry of the universe arises from a cosmological phase transition where lepton-number is spontaneously broken. If the phase transition is first order, a lepton-number asymmetry can arise at the bubble wall, through dynamics similar to electroweak baryogenesis, but involving right-handed neutrinos. In addition to the usual neutrinoless double beta decay in nuclear experiments, the model may be probed through a variety of “baryogenesis by-products,” which include a stochastic background of gravitational waves created by the colliding bubbles. Depending on the model, other aspects may include a network of topological defects that produce their own gravitational waves, additional contribution to dark radiation, and a light pseudo-Goldstone boson (majoron) as dark matter candidate.

Read this paper on arXiv…

A. Long, A. Tesi and L. Wang
Thu, 16 Mar 17
63/92

Comments: 21 pages + 10 appendices & references, 3 figures

The X-ray properties of Be/X-ray pulsars in quiescence [HEAP]

http://arxiv.org/abs/1703.04634


Observations of accreting neutron stars (NS) with strong magnetic fields can be used not only for studying the accretion flow interaction with NS magnetospheres, but also for understanding the physical processes inside NSs and for estimating their fundamental parameters. Of particular interest are (i) the interaction of a rotating neutron star (magnetosphere) with the in-falling matter at different accretion rates, and (ii) the theory of deep crustal heating and the influence of a strong magnetic field on this process. Here, we present results of the first systematic investigation of 16 X-ray pulsars with Be optical companions during their quiescent states, based on data from the Chandra, XMM-Newton and Swift observatories. The whole sample of sources can be roughly divided into two distinct groups: i) relatively bright objects with a luminosity around ~10^34 erg/s and (hard) power-law spectra, and ii) fainter ones showing thermal spectra. X-ray pulsations were detected from five objects in group i) with quite a large pulse fraction of 50-70 per cent. The obtained results are discussed within the framework of the models describing the interaction of the in-falling matter with the neutron star magnetic field and those describing heating and cooling in accreting NSs.

Read this paper on arXiv…

S. Tsygankov, R. Wijnands, A. Lutovinov, et. al.
Thu, 16 Mar 17
64/92

Comments: 17 pages, 3 figures, 3 tables, submitted to MNRAS

General dynamical properties of cosmological models with nonminimal kinetic coupling [CL]

http://arxiv.org/abs/1703.04966


We consider cosmological dynamics in the theory of gravity with the scalar field possessing the nonminimal kinetic coupling to curvature given as $\eta G^{\mu\nu}\phi_{,\mu}\phi_{,\nu}$, where $\eta$ is an arbitrary coupling parameter, and the scalar potential $V(\phi)$ which assumed to be as general as possible. With an appropriate dimensionless parameterization we represent the field equations as an autonomous dynamical system which contains ultimately only one arbitrary function $\chi (x)= 8 \pi G |\eta| V(x/\sqrt{8 \pi G})$. Then, assuming the rather general properties of $\chi(x)$, we analyze stationary points and their stability, as well as all possible asymptotical regimes of the dynamical system. It has been shown that for a broad class of $\chi(x)$ there exist attractors representing three accelerated regimes of the Universe evolution, including de Sitter expansion (or late-time inflation), the Little Rip scenario, and the Big Rip scenario. As the specific examples, we consider a power-law potential $V(\phi)=M^4(\phi/\phi_0)^\alpha$, Higgs-like potential $V(\phi)=\frac{\lambda}{4}(\phi^2-\phi_0^2)^2$, and exponential potential $V(\phi)=M^4 e^{-\phi/\phi_0}$.

Read this paper on arXiv…

J. Matsumoto and S. Sushkov
Thu, 16 Mar 17
65/92

Comments: 26 pages, 3 figures, 3 tables

Enabling New ALMA Science with Improved Support for Time-Domain Observations [IMA]

http://arxiv.org/abs/1703.04692


While the Atacama Large Millimeter/submillimeter Array (ALMA) is a uniquely powerful telescope, its impact in certain fields of astrophysics has been limited by observatory policies rather than the telescope’s innate technical capabilities. In particular, several observatory policies present challenges for observations of variable, mobile, and/or transient sources — collectively referred to here as “time-domain” observations. In this whitepaper we identify some of these policies, describe the scientific applications they impair, and suggest changes that would increase ALMA’s science impact in Cycle 6 and beyond.
Parties interested in time-domain science with ALMA are encouraged to join the ALMA Time-domain Special Interest Group (ATSIG) by signing up for the ATSIG mailing list at https://groups.google.com/group/alma-td-sig .

Read this paper on arXiv…

K. Alexander, E. Berger, G. Bower, et. al.
Thu, 16 Mar 17
66/92

Comments: 9 pages; whitepaper submitted to the ALMA Science Advisory Council; corresponding author P. K. G. Williams (pwilliams@cfa.harvard.edu)

Redshift drift of gravitational lensing [CEA]

http://arxiv.org/abs/1703.05142


We investigate the effect of the redshift drift in strong gravitational lensing. The redshift drift produces a time variation of $i)$ the apparent position of a lensed source and $ii)$ the time delay among incoming signals from different images. We dub these effects as angular drift and time delay drift, respectively, and analyze their relevance in cosmology.

Read this paper on arXiv…

O. Piattella and L. Giani
Thu, 16 Mar 17
67/92

Comments: 4 pages, 1 figure

Exponential Distance Relation and Near Resonances in the Trappist-1 Planetary System [IMA]

http://arxiv.org/abs/1703.04545


We report in this paper a new exponential relation distance of planets in the newly discovered exoplanetary system of the Trappist-1 star, and we comment on near orbital mean motion resonances among the seven planets. We predict that possible smaller planets could be found inside the orbit of the innermost discovered Planet b.

Read this paper on arXiv…

V. Pletser and L. Basano
Thu, 16 Mar 17
68/92

Comments: 6 pages, 2 figures, 5 Tables

The NuSTAR view of the true Type 2 Seyfert NGC3147 [GA]

http://arxiv.org/abs/1703.04586


We present the first NuSTAR observation of a ‘true’ Type 2 Seyfert galaxy. The 3-40 keV X-ray spectrum of NGC3147 is characterised by a simple power-law, with a standard {\Gamma}~1.7 and an iron emission line, with no need for any further component up to ~40 keV. These spectral properties, together with significant variability on time-scales as short as weeks (as shown in a 2014 Swift monitoring campaign), strongly support an unobscured line-of-sight for this source. An alternative scenario in terms of a Compton-thick source is strongly disfavoured, requiring an exceptional geometrical configuration, whereas a large fraction of the solid angle to the source is filled by a highly ionised gas, whose reprocessed emission would dominate the observed luminosity. Moreover, in this scenario the implied intrinsic X-ray luminosity of the source would be much larger than the value predicted by other luminosity proxies, like the [OIII]{\lambda}5007 emission line extinction-corrected luminosity. Therefore, we confirm with high confidence that NGC3147 is a true Type 2 Seyfert galaxy, intrinsically characterised by the absence of a BLR.

Read this paper on arXiv…

S. Bianchi, A. Marinucci, G. Matt, et. al.
Thu, 16 Mar 17
69/92

Comments: 5 pages, 5 figures, accepted for publication in MNRAS

Probing the cosmic ray mass composition in the knee region through TeV secondary particle fluxes from solar surroundings [HEAP]

http://arxiv.org/abs/1703.05083


The possibility of estimating the mass composition of primary cosmic rays above the knee of its energy spectrum through the study of high energy gamma rays, muons and neutrinos produced in the interactions of cosmic rays with the solar ambient matter and radiation has been explored. It is found that the theoretical fluxes of TeV gamma rays, muons and neutrinos from a region around $15^{o}$ of the Sun are sensitive to mass composition of cosmic rays in the PeV energy range. The experimental prospects for detection of such TeV gamma rays/neutrinos by future experiments are discussed.

Read this paper on arXiv…

P. Banik, B. Bijay, S. Sarkar, et. al.
Thu, 16 Mar 17
70/92

Comments: 10 pages, 7 figures, to appear in Physical Review D

Descattering of Giant Pulses in PSR B1957+20 [HEAP]

http://arxiv.org/abs/1703.05176


The interstellar medium scatters radio waves which causes pulsars to scintillate. For intrinsically short bursts of emission, the observed signal should be a direct measurement of the impulse response function. We show that this is indeed the case for giant pulses from PSR B1957+20: from baseband observations at 327 MHz, we demonstrate that the observed voltages of a bright pulse allow one to coherently descatter nearby ones. We find that while the scattering timescale is $12.3\,\mu$s, the power in the descattered pulses is concentrated within a span almost two orders of magnitude shorter, of $\lesssim\!200\,$ns. This sets an upper limit to the intrinsic duration of the giant pulses. We verify that the response inferred from the giant pulses is consistent with the scintillation pattern obtained by folding the regular pulsed emission, and that it decorrelates on the same timescale, of~$84\,$s. In principle, with large sets of giant pulses, it should be possible to constrain the structure of the scattering screen much more directly than with other current techniques, such as holography on the dynamic spectrum and cyclic spectroscopy.

Read this paper on arXiv…

R. Main, M. Kerkwijk, U. Pen, et. al.
Thu, 16 Mar 17
71/92

Comments: 7 pages, 5 figures

Early Science with the Large Millimeter Telescope: Detection of dust emission in multiple images of a normal galaxy at $z>4$ lensed by a Frontier Fields cluster [GA]

http://arxiv.org/abs/1703.04535


We directly detect dust emission in an optically-detected, multiply-imaged galaxy lensed by the Frontier Fields cluster MACSJ0717.5+3745. We detect two images of the same galaxy at 1.1mm with the AzTEC camera on the Large Millimeter Telescope leaving no ambiguity in the counterpart identification. This galaxy, MACS071_Az9, is at z>4 and the strong lensing model (mu=7.5) allows us to calculate an intrinsic IR luminosity of 9.7e10 Lsun and an obscured star formation rate of 14.6 +/- 4.5 Msun/yr. The unobscured star formation rate from the UV is only 4.1 +/- 0.3 Msun/yr which means the total star formation rate (18.7 +/- 4.5 Msun/yr) is dominated (75-80%) by the obscured component. With an intrinsic stellar mass of only 6.9e9Msun, MACS0717_Az9 is one of only a handful of z>4 galaxies at these lower masses that is detected in dust emission. This galaxy lies close to the estimated star formation sequence at this epoch. However, it does not lie on the dust obscuration relation (IRX-beta) for local starburst galaxies and is instead consistent with the Small Magellanic Cloud (SMC) attenuation law. This remarkable lower mass galaxy showing signs of both low metallicity and high dust content may challenge our picture of dust production in the early Universe.

Read this paper on arXiv…

A. Pope, A. Montana, A. Battisti, et. al.
Thu, 16 Mar 17
72/92

Comments: 12 pages, 6 figures, accepted for publication in ApJ

Probing Large Galaxy Halos at $z\sim0$ with Automated $\rm Ly α$-Absorption Matching [GA]

http://arxiv.org/abs/1703.04618


We present initial results from an ongoing large-scale study of the circumgalactic medium in the nearby Universe ($cz \leq 10,000$ km/s), using archival Cosmic Origins Spectrograph spectra of background quasi-stellar objects. This initial sample contains 33 sightlines chosen for their proximity to large galaxies (D > 25 kpc) and high signal-to-noise ratios (S/N > 10), yielding 48 Ly$\alpha$ absorption lines that we have paired with 33 unique galaxies, with 29 cases where multiple absorbers within a single sightline are paired with the same galaxy. We introduce a likelihood parameter to facilitate the matching of galaxies to absorption lines in a reproducible manner. We find the usual anti-correlation between Ly$\alpha$ equivalent width (EW) and impact parameter ($\rho$) when we normalize by galaxy virial radius ($R_{vir}$). Galaxies associated with a Ly$\alpha$ absorber are found to be more highly-inclined than galaxies in the survey volume at a >99% confidence level (equivalent to $\sim 3.6 \sigma$ for a normal distribution). In contrast with suggestions in other recent papers of a correlation with azimuth angle for Mg II absorption, we find no such correlation for Ly$\alpha$.

Read this paper on arXiv…

D. French and B. Wakker
Thu, 16 Mar 17
73/92

Comments: 11 pages, 13 figures

Searching for GC-like abundance patterns in young massive clusters II. – Results from the Antennae galaxies [GA]

http://arxiv.org/abs/1703.04591


The presence of multiple populations (MPs) with distinctive light element abundances is a widespread phenomenon in clusters older than 6 Gyr. Clusters with masses, luminosities, and sizes comparable to those of ancient globulars are still forming today. Nonetheless, the presence of light element variations has been poorly investigated in such young systems, even if the knowledge of the age at which this phenomenon develops is crucial for theoretical models on MPs. We use J-band integrated spectra of three young (7-40 Myr) clusters in NGC 4038 to look for Al variations indicative of MPs. Assuming that the large majority (>70%) of stars are characterised by high Al content – as observed in Galactic clusters with comparable mass; we find that none of the studied clusters show significant Al variations. Small Al spreads have been measured in all the six young clusters observed in the near-infrared. While it is unlikely that young clusters only show low Al whereas old ones display different levels of Al variations; this suggests the possibility that MPs are not present at such young ages at least among the high-mass stellar component. Alternatively, the fraction of stars with field-like chemistry could be extremely large, mimicking low Al abundances in the integrated spectrum. Finally, since the near-infrared stellar continuum of young clusters is almost entirely due to luminous red supergiants, we can also speculate that MPs only manifest themselves in low mass stars due to some evolutionary mechanism.

Read this paper on arXiv…

C. Lardo, I. Cabrera-Ziri, B. Davies, et. al.
Thu, 16 Mar 17
74/92

Comments: 7 pages, 5 figures. To be published in MNRAS

Powerful Solar Signatures of Long-Lived Dark Mediators [HEAP]

http://arxiv.org/abs/1703.04629


Dark matter capture and annihilation in the Sun can produce detectable high-energy neutrinos, providing a probe of the dark matter-proton scattering cross section. We consider the case when annihilation proceeds via long-lived dark mediators, which allows gamma rays to escape the Sun and reduces the attenuation of neutrinos. For gamma rays, there are exciting new opportunities, due to detailed measurements of GeV solar gamma rays with Fermi, and unprecedented sensitivities in the TeV range with HAWC and LHAASO. For neutrinos, the enhanced flux, particularly at higher energies ($\sim$TeV), allows a more sensitive dark matter search with IceCube and KM3NeT. We show that these search channels can be extremely powerful, potentially improving sensitivity to the dark matter spin-dependent scattering cross section by several orders of magnitude relative to present searches for high-energy solar neutrinos, as well as direct detection experiments.

Read this paper on arXiv…

R. Leane, K. Ng and J. Beacom
Thu, 16 Mar 17
75/92

Comments: 16 pages, 8 figures

Cosmic rays, gas and dust in nearby anticentre clouds : I — CO-to-H2 conversion factors and dust opacities [HEAP]

http://arxiv.org/abs/1703.05237


We aim to explore the capabilities of dust emission and rays for probing the properties of the interstellar medium in the nearby anti-centre region, using gamma-ray observations with the Fermi Large Area Telescope (LAT), and the thermal dust optical depth inferred from Planck and IRAS observations. In particular, we aim at quantifying potential variations in cosmic-ray density and dust properties per gas nucleon across the different gas phases and different clouds, and at measuring the CO-to-H2 conversion factor, X$_{CO}$ , in different environments. We have separated six nearby anti-centre clouds that are coherent in velocities and distances, from the Galactic-disc background in HI 21-cm and $^{12}$CO 2.6-mm line emission. We have jointly modelled the gamma-ray intensity recorded between 0.4 and 100 GeV, and the dust optical depth at 353 GHz as a combination of HI-bright, CO-bright, and ionised gas components. The complementary information from dust emission and gamma rays was used to reveal the gas not seen, or poorly traced, by HI , free-free, and $^{12}$CO emissions, namely (i) the opaque HI and diffuse H$_2$ present in the Dark Neutral Medium at the atomic-molecular transition, and (ii) the dense H$_2$ to be added where $^{12}$CO lines saturate. The measured interstellar gamma-ray spectra support a uniform penetration of the cosmic rays with energies above a few GeV through the clouds. We find a gradual increase in grain opacity as the gas becomes more dense. The increase reaches a factor of four to six in the cold molecular regions that are well shielded from stellar radiation. Consequently, the X$_{CO}$ factor derived from dust is systematically larger by 30% to 130% than the gamma-ray estimate. We also evaluate the average gamma-ray X$_{CO}$ factorfor each cloud, and find that X$_{CO}$ tends to decrease from diffuse to more compact molecular clouds, as expected from theory.

Read this paper on arXiv…

Q. Remy, I. Grenier, D. Marshall, et. al.
Thu, 16 Mar 17
76/92

Comments: N/A

The metal rich abundance pattern – spectroscopic properties and abundances for 107 main-sequence stars [SSA]

http://arxiv.org/abs/1703.05077


We report results from the high resolution spectral analysis of the 107 metal rich (mostly [Fe/H]$\ge$7.67 dex) target stars from the Calan-Hertfordshire Extrasolar Planet Search program observed with HARPS. Using our procedure of finding the best fit to the absorption line profiles in the observed spectra, we measure the abundances of Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn, and we then compare them with known results from different authors. Most of our abundances agree with these works at the level of $\pm$0.05 dex or better for the stars we have in common. However, we do find systematic differences that make direct inferences difficult. Our analysis suggests that the selection of line lists and atomic line data along with the adopted continuum level influence these differences the most. At the same time, we confirm the positive trends of abundances versus metallicity for Na, Mn, Ni, and to a lesser degree, Al. A slight negative trend is observed for Ca, whereas Si and Cr tend to follow iron. Our analysis allows us to determine the positively skewed normal distribution of projected rotational velocities with a maximum peaking at 3 km s$^{-1}$. Finally, we obtained a Gaussian distribution of microturbulent velocities that has a maximum at 1.2 km s$^{-1}$ and a full width at half maximum $\Delta v_{1/2}=$0.35 km s$^{-1}$, indicating that metal rich dwarfs and subgiants in our sample have a very restricted range in microturbulent velocity.

Read this paper on arXiv…

O. Ivanyuk, J. Jenkins, Y. Pavlenko, et. al.
Thu, 16 Mar 17
77/92

Comments: To be published in the Monthly Notices of the Royal Astronomical Society

Dark-ages Reionization and Galaxy Formation Simulation X. The small contribution of quasars to reionization [CEA]

http://arxiv.org/abs/1703.04895


Motivated by recent measurements of the number density of faint AGN at high redshift, we investigate the contribution of quasars to reionization by tracking the growth of central supermassive black holes in an update of the {\sc Meraxes} semi-analytic model. The model is calibrated against the observed stellar mass function at $z{\sim}0.6{-}7$, the black hole mass function at $z{\lesssim}0.5$, the global ionizing emissivity at $z{\sim}2{-}5$, and the Thomson scattering optical depth. The model reproduces a Magorrian relation in agreement with observations at $z{<}0.5$, and predicts a decreasing black hole mass towards higher redshifts at fixed total stellar mass. With the implementation of an opening angle of $80$ degrees for quasar radiation, corresponding to an observable fraction of ${\sim}23.4$ per cent due to obscuration by dust, the model is able to reproduce the observed quasar luminosity function at $z{\sim}0.6{-}6$. The stellar light from galaxies hosting faint AGN contributes a significant or dominant fraction of the UV flux. At high redshift, the model is consistent with the bright end quasar luminosity function and suggests that the recent faint $z{\sim}4$ AGN sample compiled by \citet{Giallongo2015} includes a significant fraction of stellar light. Direct application of this luminosity function to the calculation of AGN ionizing emissivity consequently overestimates the number of ionizing photons produced by quasars by a factor of 3 at $z{\sim}6$. We conclude that quasars are unlikely to make a significant contribution to reionization.

Read this paper on arXiv…

Y. Qin, S. Mutch, G. Poole, et. al.
Thu, 16 Mar 17
78/92

Comments: 20 pages, 11 figures, submitted to MNRAS, comments are welcome

(Almost) Dark Galaxies in the ALFALFA Survey: Isolated HI Bearing Ultra Diffuse Galaxies [GA]

http://arxiv.org/abs/1703.05293


We present a sample of 115 very low optical surface brightness, highly extended, HI-rich galaxies carefully selected from the ALFALFA survey that have similar optical absolute magnitudes, surface brightnesses, and radii to recently discovered “ultra-diffuse” galaxies (UDGs). However, these systems are bluer and have more irregular morphologies than other UDGs, are isolated, and contain significant reservoirs of HI. We find that while these sources have normal star formation rates for HI selected galaxies of similar stellar mass, they have very low star formation efficiencies. We further present deep optical and HI synthesis follow up imaging of three of these HI-bearing ultra-diffuse sources. We measure HI diameters extending to ~40 kpc, but note that while all three sources have large HI diameters for their stellar mass, they are consistent with the HI mass – HI radius relation. We further analyze the HI velocity widths and rotation velocities for the unresolved and resolved sources respectively, and find that the sources appear to inhabit halos of dwarf galaxies. We estimate spin parameters, and suggest that these sources may exist in high spin parameter halos, and as such may be potential HI-rich progenitors to the ultra-diffuse galaxies observed in cluster environments.

Read this paper on arXiv…

L. Leisman, M. Haynes, S. Janowiecki, et. al.
Thu, 16 Mar 17
79/92

Comments: 18 pages, 8 figures, resubmitted to ApJ after revisions based on reviewer comments

LSDCat: Detection and cataloguing of emission line sources in integral-field spectroscopy datacubes [IMA]

http://arxiv.org/abs/1703.05166


We present a robust, efficient, and user-friendly algorithm for detecting faint emission line sources in large integral-field spectroscopic datacubes. together with the public release of the software package LSDCat (Line Source Detection and Cataloguing). LSDCat uses a 3-dimensional matched filter approach, combined with thresholding in signal-to-noise, to build a catalogue of individual line detections. In a second pass, the detected lines are grouped into distinct objects, and positions, spatial extents, and fluxes of the detected lines are determined. LSDCat requires only a small number of input parameters, and we provide guidelines for choosing appropriate values. The software is coded in Python and capable to process very large datacubes in a short time. We verify the implementation with a source insertion and recovery experiment utilising a real datacube taken with the MUSE instrument at the ESO Very Large Telescope.

Read this paper on arXiv…

E. Herenz and L. Wisotzki
Thu, 16 Mar 17
80/92

Comments: 14 pages. Accepted for publication in Astronomy & Astrophysics. The LSDCat software is available at this https URL

On the Chemistry of the Young Massive Protostellar core NGC 2264 CMM3 [GA]

http://arxiv.org/abs/1703.04632


We present the first gas-grain astrochemical model of the NGC 2264 CMM3 protostellar core. The chemical evolution of the core is affected by changing its physical parameters such as the total density and the amount of gas-depletion onto grain surfaces as well as the cosmic ray ionisation rate, $\zeta$. We estimated $\zeta_{\text {CMM3}}$ = 1.6 $\times$ 10$^{-17}$ s$^{-1}$. This value is 1.3 times higher than the standard CR ionisation rate, $\zeta_{\text {ISM}}$ = 1.3 $\times$ 10$^{-17}$ s$^{-1}$. Species response differently to changes into the core physical conditions, but they are more sensitive to changes in the depletion percentage and CR ionisation rate than to variations in the core density. Gas-phase models highlighted the importance of surface reactions as factories of large molecules and showed that for sulphur bearing species depletion is important to reproduce observations.
Comparing the results of the reference model with the most recent millimeter observations of the NGC 2264 CMM3 core showed that our model is capable of reproducing the observed abundances of most of the species during early stages ($\le$ 3$\times$10$^4$ yrs) of their chemical evolution. Models with variations in the core density between 1 – 20 $\times$ 10$^6$ cm$^{-3}$ are also in good agreement with observations during the early time interval 1 $\times$ 10$^4 <$ t (yr) $<$ 5 $\times$ 10$^4$. In addition, models with higher CR ionisation rates (5 – 10) $\times \zeta_{\text {ISM}}$ are often overestimating the fractional abundances of the species. However, models with $\zeta_{\text {CMM3}}$ = 5 $\zeta_{\text {ISM}}$ may best fit observations at times $\sim$ 2 $\times$ 10$^4$ yrs. Our results suggest that CMM3 is (1 – 5) $\times$ 10$^4$ yrs old. Therefore, the core is chemically young and it may host a Class 0 object as suggested by previous studies.

Read this paper on arXiv…

Z. Awad and O. Shalabeia
Thu, 16 Mar 17
81/92

Comments: 24 pages, 4 figures, 3 Tables. Accepted for publication in Astrophysics and Space Science

Photometry of the long period dwarf nova GY Hya [SSA]

http://arxiv.org/abs/1703.04712


Although comparatively bright, the cataclysmic variable GY Hya has not attracted much attention in the past. As part of a project to better characterize such systems photometrically, we observed light curves in white light, each spanning several hours, at Bronberg Observatory, South Africa, in 2004 and 2005, and at the Observat\’orio do Pico dos Dias, Brazil, in 2014 and 2016. These data permit to study orbital modulations and their variations from season to season. The orbital period, already known from spectroscopic observations of Peters & Thorstensen (2005), is confirmed through strong ellipsoidal variations of the mass donor star in the system and the presence of eclipses of both components. A refined period of 0.34723972~(6) days and revised ephemeris are derived. Seasonal changes in the average orbital light curve can qualitatively be explained by variations of the contribution of a hot spot to the system light together with changes of the disk radius. The amplitude of the ellipsoidal variations and the eclipse contact phases permit to put some constraints on the mass ratio, orbital inclination and the relative brightness of the primary and secondary components. There are some indications that the disk radius during quiescence, expressed in units of the component separation, is smaller than in other dwarf novae.

Read this paper on arXiv…

A. Bruch and B. Monard
Thu, 16 Mar 17
82/92

Comments: N/A

Priors on the effective Dark Energy equation of state in scalar-tensor theories [CEA]

http://arxiv.org/abs/1703.05297


Constraining the Dark Energy (DE) equation of state, w, is one of the primary science goals of ongoing and future cosmological surveys. In practice, with imperfect data and incomplete redshift coverage, this requires making assumptions about the evolution of w with redshift z. These assumptions can be manifested in a choice of a specific parametric form, which can potentially bias the outcome, or else one can reconstruct w(z) non-parametrically, by specifying a prior covariance matrix that correlates values of w at different redshifts. In this work, we derive the theoretical prior covariance for the effective DE equation of state predicted by general scalar-tensor theories with second order equations of motion (Horndeski theories). This is achieved by generating a large ensemble of possible scalar-tensor theories using a Monte Carlo methodology, including the application of physical viability conditions. We also separately consider the special sub-case of the minimally coupled scalar field, or quintessence. The prior shows a preference for tracking behaviors in the most general case. Given the covariance matrix, theoretical priors on parameters of any specific parametrization of w(z) can also be readily derived by projection.

Read this paper on arXiv…

M. Raveri, P. Bull, A. Silvestri, et. al.
Thu, 16 Mar 17
83/92

Comments: 13 pages, 5 figures

Degeneracy in the spectrum and bispectrum among featured inflaton potentials [CEA]

http://arxiv.org/abs/1703.04621


We study the degeneracy of the primordial spectrum and bispectrum of the curvature perturbation in single field inflationary models with a class of features in the inflaton potential. The feature we consider is a discontinuous change in the shape of the potential and is controlled by a couple of parameters that describe the strength of the discontinuity and the change in the potential shape. This feature produces oscillations of the spectrum and bispectrum around the comoving scale $k=k_0$ that exits the horizon when the inflaton passes the discontinuity. We find that the effects on the spectrum and almost all configurations of the bispectrum including the squeezed limit depend on a single quantity which is a function of the two parameters defining the feature. This leads to a degeneracy, i.e. different features of the inflaton potential can produce the same observational effects. However, we find that the degeneracy in the bispectrum is removed at the equilateral limit around $k=k_0$. This can be used to discriminate different models which give the same spectrum.

Read this paper on arXiv…

A. Cadavid, A. Romano and M. Sasaki
Thu, 16 Mar 17
84/92

Comments: N/A

Probing the Interstellar Dust towards the Galactic Centre: Dust Scattering Halo around AX J1745.6-2901 [HEAP]

http://arxiv.org/abs/1703.05179


AX J1745.6-2901 is an X-ray binary located at only 1.45 arcmin from Sgr A*, showcasing a strong X-ray dust scattering halo. We combine Chandra and XMM-Newton observations to study the halo around this X-ray binary. Our study shows two major thick dust layers along the line of sight (LOS) towards AX J1745.6-2901. The LOS position and $N_{H}$ of these two layers depend on the dust grain models with different grain size distribution and abundances. But for all the 19 dust grain models considered, dust Layer-1 is consistently found to be within a fractional distance of 0.11 (mean value: 0.05) to AX J1745.6-2901 and contains only (19-34)% (mean value: 26%) of the total LOS dust. The remaining dust is contained in Layer-2, which is distributed from the Earth up to a mean fractional distance of 0.64. A significant separation between the two layers is found for all the dust grain models, with a mean fractional distance of 0.31. Besides, an extended wing component is discovered in the halo, which implies a higher fraction of dust grains with typical sizes $\lesssim$ 590 \AA\ than considered in current dust grain models. Assuming AX J1745.6-2901 is 8 kpc away, dust Layer-2 would be located in the Galactic disk several kpc away from the Galactic Centre (GC). The dust scattering halo biases the observed spectrum of AX J1745.6-2901 severely in both spectral shape and flux, and also introduces a strong dependence on the size of the instrumental point spread function and the source extraction region. We build Xspec models to account for this spectral bias, which allow us to recover the intrinsic spectrum of AX J1745.6-2901 free from dust scattering opacity. If dust Layer-2 also intervenes along the LOS to Sgr A* and other nearby GC sources, a significant spectral correction for the dust scattering opacity would be necessary for all these GC sources.

Read this paper on arXiv…

C. Jin, G. Ponti, F. Haberl, et. al.
Thu, 16 Mar 17
85/92

Comments: 20 pages, 18 figures, 5 tables, accepted for publication in MNRAS

Origin of the fundamental plane of elliptical galaxies in the Coma Cluster without fine-tuning [GA]

http://arxiv.org/abs/1703.05163


After thirty years of the discovery of the fundamental plane, explanations to the tilt of the fundamental plane with respect to the virial plane still suffer from the need of fine-tuning. In this paper, we try to explore the origin of this tilt from the perspective of modified Newtonian dynamics (MOND) by applying the 16 Coma galaxies available in Thomas et al.[1]. Based on the mass models that can reproduce de Vaucouleurs’ law closely, we find that the tilt of the traditional fundamental plane is naturally explained by the simple form of the MONDian interpolating function, if we assume a well motivated choice of anisotropic velocity distribution, and adopt the Kroupa or Salpeter stellar mass-to-light ratio. Our analysis does not necessarily rule out a varying stellar mass-to-light ratio.

Read this paper on arXiv…

M. Chiu, C. Ko and C. Shu
Thu, 16 Mar 17
86/92

Comments: N/A

Non-cyclic geometric phases and helicity transitions for neutrino oscillations in magnetic field [CL]

http://arxiv.org/abs/1703.05027


We show that neutrino spin and spin-flavor transitions involve non-vanishing geometric phases. Analytical expressions are derived for non-cyclic geometric phases arising due to neutrino oscillations in magnetic fields and matter. Several calculations are performed for different cases of rotating and non-rotating magnetic fields in the context of solar neutrinos and neutrinos produced inside neutron stars. It is shown that the neutrino eigenstates carry non-vanishing geometric phases even at large distances from their original point of production. Also the effects of critical magnetic fields and cross boundary effects in case of neutrinos emanating out of neutron stars are analyzed.

Read this paper on arXiv…

S. Joshi and S. Jain
Thu, 16 Mar 17
87/92

Comments: 12 pages, 7 figures

XMM-Newton and NuSTAR simultaneous X-ray observations of IGR J11215-5952 [HEAP]

http://arxiv.org/abs/1703.05030


We report the results of an XMM-Newton and NuSTAR coordinated observation of the Supergiant Fast X-ray Transient (SFXT) IGRJ11215-5952, performed on February 14, 2016, during the expected peak of its brief outburst, which repeats every about 165 days. Timing and spectral analysis were performed simultaneously in the energy band 0.4-78 keV. A spin period of 187.0 +/- 0.4 s was measured, consistent with previous observations performed in 2007. The X-ray intensity shows a large variability (more than one order of magnitude) on timescales longer than the spin period, with several luminous X-ray flares which repeat every 2-2.5 ks, some of which simultaneously observed by both satellites. The broad-band (0.4-78 keV) time-averaged spectrum was well deconvolved with a double-component model (a blackbody plus a power-law with a high energy cutoff) together with a weak iron line in emission at 6.4 keV (equivalent width, EW, of 40+/-10 eV). Alternatively, a partial covering model also resulted in an adequate description of the data. The source time-averaged X-ray luminosity was 1E36 erg/s (0.1-100 keV; assuming 7 kpc). We discuss the results of these observations in the framework of the different models proposed to explain SFXTs, supporting a quasi-spherical settling accretion regime, although alternative possibilities (e.g. centrifugal barrier) cannot be ruled out.

Read this paper on arXiv…

L. Sidoli, A. Tiengo, A. Paizis, et. al.
Thu, 16 Mar 17
88/92

Comments: 13 pages, 11 figures, accepted for publication on The Astrophysical Journal

WISE J080822.18-644357.3 – a 45 Myr-old accreting M dwarf hosting a pre-transitional disc [SSA]

http://arxiv.org/abs/1703.04544


WISE J080822.18-644357.3 (WISE J0808-6443) was recently identified as a new M dwarf debris disc system and a candidate member of the 45 Myr-old Carina association. Given that the strength of its infrared excess ($L_{\mathrm{IR}}/L_{\mathrm{\star}}$ ~ 0.1) appears to be more consistent with a young protoplanetary disc, we present the first optical spectra of the star and reassess its evolutionary and membership status. We find WISE J0808-6443 to be a Li-rich M5 star with strong H$\alpha$ emission ($-125 \lt$ EW $\lt -65$ Ang over 4 epochs) whose strength and broad width are consistent with accretion at a low level ($\sim 10^{-10} M_{\odot} yr^{-1}$) from its disc. The spectral energy distribution of the star is consistent with a two-temperature disc structure, with a hot inner disc ($T_{\mathrm{in}}$ ~ 1100 K) at orbital radius ~0.006 au and a warm outer disc ($T_{\mathrm{out}}$ ~ 230 K) at radius ~0.12 au. The dust belts likely correspond to the sublimation temperatures of silicates and icy planetesimals, respectively. We calculate an improved proper motion based on archival astrometry, and combined with a new radial velocity, the kinematics of the star are consistent with membership in Carina at a kinematic distance of $90\pm9$ pc. The spectroscopic and photometric data are consistent with WISE J0808-6443 being a $\sim 0.1 M_{\odot}$ Classical T-Tauri star and one of the oldest known accreting M-type stars. These results suggest that the upper limit on the lifetimes of gas-rich discs around the lowest mass stars may be longer than previously recognised, or some mechanism may be responsible for regenerating short-lived discs at later stages of pre-main sequence evolution. Low-level accretion for tens of Myr may provide a mechanism for the migration, eccentricity dampening, and resonance locking of small planets, like those recently reported for the TRAPPIST-1 exoplanetary system.

Read this paper on arXiv…

S. Murphy, E. Mamajek and C. Bell
Thu, 16 Mar 17
89/92

Comments: Submitted to MNRAS; 9 pages, 9 figures and 5 tables

The igmspec Database of Public Spectra Probing the Intergalactic Medium [CEA]

http://arxiv.org/abs/1703.04695


We describe v02 of igmspec, a database of publically available ultraviolet, optical, and near-infrared spectra that probe the intergalactic medium (IGM). This database, a child of the specdb repository in the specdb github organization, comprises 403277 unique sources and 434686 spectra obtained with the world’s greatest observatories. All of these data are distributed in a single ~25 GB HDF5 file maintained at the University of California Observatories and the University of California, Santa Cruz. The specdb software package includes Python scripts and modules for searching the source catalog and spectral datasets, and software links to the linetools package for spectral analysis. The repository also includes software to generate private spectral datasets that are compliant with International Virtual Observatory Alliance (IVOA) protocols and a Python-based interface for IVOA Simple Spectral Access queries. Future versions of igmspec will ingest other sources (e.g. gamma-ray burst afterglows) and other surveys as they become publicly available. The overall goal is to include every spectrum that effectively probes the IGM. Future databases of specdb may include publicly available galaxy spectra (exgalspec) and published supernovae spectra (snspec). The community is encouraged to join the effort on github: https://github.com/specdb

Read this paper on arXiv…

J. Prochaska
Thu, 16 Mar 17
90/92

Comments: Accepted to Astronomy & Computing; 21 pages, 1 figure; join this https URL and clone this https URL

Space- and time-correlations in the supernova driven interstellar medium [GA]

http://arxiv.org/abs/1703.05187


We apply correlation analysis to random velocity, density and magnetic fields in numerical simulations of the supernova-driven interstellar medium (ISM). We solve the thermo-magnetohydrodynamic (MHD) equations in a shearing, Cartesian box representing a local region of the ISM, subject to thermal and kinetic energy injection by supernova explosions, and parametrized optically-thin radiative cooling. We consider the cold, warm and hot phases of the ISM separately; the analysis mostly considers the warm gas, which occupies the bulk of the simulation volume. Various physical variables have different correlation lengths in the warm phase: $40{\,{\rm pc}}$, $50{\,{\rm pc}}$, and $60{\,{\rm pc}}$ for magnetic field, density, and velocity, respectively, in the midplane. The correlation time of the random velocity field is comparable to the eddy turnover time, about $10^7{\,{\rm yr}}$, although it may be shorter in regions with higher star formation rate. The random magnetic field is anisotropic, with the standard deviations of its components $b_x/b_y/b_z$ having the approximate ratios $0.5/0.6/0.6$ in the midplane. The anisotropy is attributed to the global velocity shear from galactic differential rotation, and locally inhomogeneous outflow to the galactic halo. The correlation length of Faraday depth along the $z$-axis, $120{\,{\rm pc}}$, is greater than for electron density, $60 \unicode{x2013} 90{\,{\rm pc}}$, and vertical magnetic field, $60{\,{\rm pc}}$. Such comparisons may be sensitive to the orientation of the line of sight. Uncertainties of the structure functions of the synchrotron intensity rapidly increase with the scale. This feature is hidden in power spectrum analysis, which can undermine the usefulness of power spectra for detailed studies of interstellar turbulence.

Read this paper on arXiv…

J. Hollins, G. Sarson, A. Shukurov, et. al.
Thu, 16 Mar 17
91/92

Comments: 14 pages, 16 figures

CO$_2$ condensation is a serious limit to the deglaciation of Earth-like planets [EPA]

http://arxiv.org/abs/1703.04624


It is widely believed that the carbonate-silicate cycle is the main agent to trigger deglaciations by CO$_2$ greenhouse warming on Earth and on Earth-like planets when they get in frozen state. Here we use a 3D Global Climate Model to simulate the ability of frozen planets to escape from glaciation by accumulating enough gaseous CO$_2$.
We find that Earth-like planets orbiting a Sun-like star may never be able to escape from glaciation if their orbital distance is greater than $\sim$ 1.27 AU (Flux $<$ 847 W m$^{-2}$), because CO$_2$ would condense at the poles forming permanent CO$_2$ ice caps. This limits the amount of CO$_2$ in the atmosphere and thus its greenhouse effect.
The amount of CO$_2$ that can be trapped in the polar caps depends on the efficiency of CO$_2$ ice to flow laterally as well as its graviational stability relative to subsurface water ice.
The flow of CO$_2$ ice from poles to equator is mostly controlled by the bottom temperature, and hence by the internal heat flux. We find that a frozen Earth-like planet located at 1.30 AU of a Sun-like star could store as much as 1.5/4.5/15 bars of dry ice at the poles, for internal heat fluxes of 100/30/10 mW m$^{-2}$.
But these amounts are lower limits. For planets with a significant water ice cover, we show that CO$_2$ ice deposits should be gravitationnally unstable. They get burried beneath the water ice cover in short timescales of 10$^2$-10$^3$ yrs, mainly controlled by the viscosity of water ice. For water ice cover exceeding about 300 m, we show that the CO$_2$ would be permanently sequestred underneath the water ice cover, in the form of CO$_2$ liquids, CO$_2$ clathrate hydrates and/or dissolved in subglacial water reservoirs (if any). This would considerably increase the amount of CO$_2$ trapped and further reduce the probability of deglaciation.

Read this paper on arXiv…

M. Turbet, F. Forget, J. Leconte, et. al.
Thu, 16 Mar 17
92/92

Comments: Submitted – Comments are welcome

Digital receivers for low-frequency radio telescopes UTR-2, URAN, GURT [IMA]

http://arxiv.org/abs/1703.04384


This paper describes digital radio astronomical receivers used for decameter and meter wavelength observations. This paper describes digital radio astronomical receivers used for decameter and meter wavelength observations. Since 1998, digital receivers performing on-the-fly dynamic spectrum calculations or waveform data recording without data loss have been used at the UTR-2 radio telescope, the URAN VLBI system, and the GURT new generation radio telescope. Here we detail these receivers developed for operation in the strong interference environment that prevails in the decameter wavelength range. Data collected with these receivers allowed us to discover numerous radio astronomical objects and phenomena at low frequencies, a summary of which is also presented.

Read this paper on arXiv…

V. Zakharenko, A. Konovalenko, P. Zarka, et. al.
Tue, 14 Mar 17
1/74

Comments: 24 pages, 15 figures

Indication of a massive circumbinary planet orbiting the Low Mass X-ray Binary MXB 1658-298 [HEAP]

http://arxiv.org/abs/1703.04433


We present an X-ray timing analysis of the transient X-ray binary MXB 1658-298, using data obtained from the RXTE and XMM-Newton observatories. We have made 27 new mid eclipse time measurements from observations made during the two outbursts of the source. These new measurements have been combined with the previously known values to study long term changes in orbital period of the binary system. We have found that the mid-eclipse timing record of MXB 1658-298 is quite unusual. The long term evolution of mid-eclipse times indicates an overall orbital period decay with a time scale of — 6.5(7) x 10^7 year. Over and above this orbital period decay, the O-C residual curve also shows a periodic residual on shorter timescales. This sinusoidal variation has an amplitude of ~9 lt-sec and a period of ~760 d. This is indicative of presence of a third body around the compact X-ray binary. The mass and orbital radius of the third body are estimated to lie in the range, 20.5-26.9 Jupiter mass and 750-860 lt-sec, respectively. If true, then it will be the most massive circumbinary planet and also the smallest period binary known to host a planet.

Read this paper on arXiv…

C. Jain, B. Paul, R. Sharma, et. al.
Tue, 14 Mar 17
2/74

Comments: 5 pages, 3 figures, Accepted for publication in Monthly Notices of the Royal Astronomical Society Letters

Multi-frequency VLBA Polarimetry of the high-redshift GPS Quasar OQ172 [GA]

http://arxiv.org/abs/1703.04066


Multi-frequency Very Long Baseline Array (VLBA) polarimetry observation of the GHz-Peaked Spectrum (GPS) quasar OQ172 (J1445+0958) has been performed at 1.6, 2.2, 4.8, 8.3 and 15.3 GHz in 2005. Core-jet structures are detected in all bands with the jet strongly bent at about 3 mas from the core. The radio emission of the source is polarised at all five bands. We study the Faraday Rotation in the core and jet components at all five bands, and find good linear fits of Faraday Rotation in the core and jet components at 4.8 and 8.3 GHz. At these two frequencies, the Rotation Measure (RM) is $\sim 2000~\rm rad~m^{-2}$ in the core and $\sim 700~\rm rad~m^{-2}$ in the inner jet components and continues to decrease at the outer jet parts. We find that the depolarisation at 4.8 and 8.3 GHz might be caused by the internal medium in the source. We investigate consistency of the turnover spectra of VLBI components with the Synchrotron Self-Absorption (SSA) and Free-Free Absorption (FFA) models. Although these two models can not be easily distinguished due to the lack of low-frequency data, the physical parameters can be constrained for each model. We find that the large width of the $\rm [OIII]_{5007}$ line is likely caused by a jet interaction with a Narrow Line Region (NLR) medium. The jet bending, significant RM variations, Faraday depolarisation, spectral turnover, and broad line width of $\rm [OIII]_{5007}$ could be closely related, likely caused by the same nucleus medium, presumably NLR.

Read this paper on arXiv…

Y. Liu, D. Jiang, M. Gu, et. al.
Tue, 14 Mar 17
3/74

Comments: 16 pages, 7 figures, accepted for publication in MNRAS

The X-ray continuum time-lags and intrinsic coherence in AGN [HEAP]

http://arxiv.org/abs/1703.04322


We present the results from a systematic analysis of the X-ray continuum (`hard’) time-lags and intrinsic coherence between the $2-4\,\mathrm{keV}$ and various energy bands in the $0.3-10\,\mathrm{keV}$ range, for ten X-ray bright and highly variable active galactic nuclei (AGN). We used all available archival \textit{XMM-Newton} data, and estimated the time-lags following Epitropakis \& Papadakis (2016). By performing extensive numerical simulations, we arrived at useful guidelines for computing intrinsic coherence estimates that are minimally biased, have known errors, and are (approximately) Gaussian distributed. Owing to the way we estimated the time-lags and intrinsic coherence, we were able to do a proper model fitting to the data. Regarding the continuum time-lags, we are able to demonstrate that they have a power-law dependence on frequency, with a slope of $-1$, and that their amplitude scales with the logarithm of the light-curve mean-energy ratio. We also find that their amplitude increases with the square root of the X-ray Eddington ratio. Regarding the intrinsic coherence, we found that it is approximately constant at low frequencies. It then decreases exponentially at frequencies higher than a characteristic `break frequency.’ Both the low-frequency constant intrinsic-coherence value and the break frequency have a logarithmic dependence on the light-curve mean-energy ratio. Neither the low-frequency constant intrinsic-coherence value, nor the break frequency exhibit a universal scaling with either the central black hole mass, or the the X-ray Eddington ratio. Our results could constrain various theoretical models of AGN X-ray variability.

Read this paper on arXiv…

A. Epitropakis and I. Papadakis
Tue, 14 Mar 17
4/74

Comments: 36 pages, 6 tables, 42 figures (accepted for publication in MNRAS)

Do FRB Mark Dark Core Collapse? [HEAP]

http://arxiv.org/abs/1703.04226


Are some neutron stars produced without a supernova, without ejecting mass in a remnant? Theoretical calculations of core collapse in massive stars often predict this. The observation of the repeating FRB 121102, whose dispersion measure has not changed over several years, suggests that dark core collapses are not just failures of computer codes, but may be real. The existence of one repeating FRB with unchanging dispersion measure is not conclusive, but within a decade hundreds or thousands of FRB are expected to be discovered, likely including scores of repeaters, permitting useful statistical inferences. A na\”{\i}ve supernova remnant model predicts observable decline in dispersion measure for 100 years after its formation. If an upper limit on the decline of 2 pc/cm$^3$-y is set for five repeating FRB, then the na\”{\i}ve model is rejected at the 95\% level of confidence. This may indicate dark neutron star formation without a supernova or supernova remnant. This hypothesis may also be tested with LSST data that would show, if present, a supernova at an interferometric FRB position if it occurred within the LSST epoch.

Read this paper on arXiv…

J. Katz
Tue, 14 Mar 17
5/74

Comments: 4 pp

Determination of the Magnetic Fields of Magellanic X-Ray Pulsars [HEAP]

http://arxiv.org/abs/1703.03885


The 80 high-mass X-ray binary (HMXB) pulsars that are known to reside in the Magellanic Clouds (MCs) have been observed by the XMM-Newton and Chandra X-ray telescopes on a regular basis for 15 years, and the XMM-Newton and Chandra archives contain nearly complete information about the duty cycles of the sources with spin periods P_S < 100 s. We have rerprocessed the archival data from both observatories and we combined the output products with all the published observations of 31 MC pulsars with P_S < 100 s in an attempt to investigate the faintest X-ray emission states of these objects that occur when accretion to the polar caps proceeds at the smallest possible rates. These states determine the so-called propeller lines of the accreting pulsars and yield information about the magnitudes of their surface magnetic fields. We have found that the faintest states of the pulsars segregate into five discrete groups which obey to a high degree of accuracy the theoretical relation between spin period and X-ray luminosity. So the entire population of these pulsars can be described by just five propeller lines and the five corresponding magnetic moments (0.29, 0.53, 1.2, 2.9, and 7.3, in units of 10^30 G cm^3).

Read this paper on arXiv…

D. Christodoulou, S. Laycock, J. Yang, et. al.
Tue, 14 Mar 17
6/74

Comments: To appear in Reserch in Astronomy and Astrophysics

The evolution of the Tully-Fisher relation between $z\sim2.3$ and $z\sim0.9$ with KMOS$^{\rm 3D}$ [GA]

http://arxiv.org/abs/1703.04321


We investigate the stellar mass and baryonic mass Tully-Fisher relations (TFRs) of massive star-forming disk galaxies at redshift $z\sim2.3$ and $z\sim0.9$ as part of the KMOS$^{\rm 3D}$ integral field spectroscopy survey. Our spatially resolved data allow reliable modelling of individual galaxies, including the effect of pressure support on the inferred gravitational potential. At fixed circular velocity, we find higher baryonic masses and similar stellar masses at $z\sim2.3$ as compared to $z\sim0.9$. Together with the decreasing gas-to-stellar mass ratios with decreasing redshift, this implies that the contribution of dark matter to the dynamical mass at the galaxy scale increases towards lower redshift. A comparison to local relations reveals a negative evolution of the stellar and baryonic TFR zero-points from $z=0$ to $z\sim0.9$, no evolution of the stellar TFR zero-point from $z\sim0.9$ to $z\sim2.3$, but a positive evolution of the baryonic TFR zero-point from $z\sim0.9$ to $z\sim2.3$. We discuss a toy model of disk galaxy evolution to explain the observed, non-monotonic TFR evolution, taking into account the empirically motivated redshift dependencies of galactic gas fractions, and of the relative amount of baryons to dark matter on the galaxy and halo scales.

Read this paper on arXiv…

H. Ubler, N. Schreiber, R. Genzel, et. al.
Tue, 14 Mar 17
7/74

Comments: 25 pages, 14 figures, submitted to ApJ

Constructing Gravitational Waves from Generic Spin-Precessing Compact Binary Inspirals [CL]

http://arxiv.org/abs/1703.03967


The coalescence of compact objects is one of the most promising sources of gravitational waves for ground-based interferometric detectors, such as advanced LIGO and Virgo. Generically, com- pact objects in binaries are expected to be spinning with spin angular momenta misaligned with the orbital angular momentum, causing the orbital plane to precess. This precession adds rich structure to the gravitational waves, introducing such complexity that an analytic closed-form description has been unavailable until now. We here construct the first closed-form frequency- domain gravitational waveforms that are valid for generic spin-precessing quasicircular compact binary inspirals. We first construct time-domain gravitational waves by solving the post-Newtonian precession equations of motion with radiation reaction through multiple scale analysis. We then Fourier transform these time-domain waveforms with the method of shifted uniform asymptotics to obtain closed-form expressions for frequency-domain waveforms. We study the accuracy of these analytic, frequency-domain waveforms relative to waveforms obtained by numerically evolving the post-Newtonian equations of motion and find that they are suitable for unbiased parameter estimation for 99.2%(94.6%) of the binary configurations we studied at a signal-to-noise ratio of 10(25). These new frequency-domain waveforms could be used for detection and parameter estimation studies due to their accuracy and low computational cost.

Read this paper on arXiv…

K. Chatziioannou, A. Klein, N. Yunes, et. al.
Tue, 14 Mar 17
8/74

Comments: 21 pages, submitted to Phys. Rev. D

Radial modes of levitating atmospheres around Eddington-luminosity neutron stars [HEAP]

http://arxiv.org/abs/1703.04224


We consider an optically thin radiation-supported levitating atmosphere suspended well above the stellar surface, as discussed recently in the Schwarzschild metric for a star of luminosity close to the Eddington value. Assuming the atmosphere to be geometrically thin and polytropic, we investigate the eigenmodes and calculate the frequencies of the oscillations of the atmosphere in Newtonian formalism. The ratio of the two lowest eigenfrequencies is $\sqrt{\gamma+1}$, i.e., it only depends on the adiabatic index.

Read this paper on arXiv…

D. Bollimpalli and W. Kluzniak
Tue, 14 Mar 17
9/74

Comments: 6 pages, 3 figures, Submitted for publication to MNRAS

A Unique View of AGN-Driven Molecular Outflows: The Discovery of a Massive Galaxy Counterpart to a $z=2.4$ High-Metallicity Damped Lyman-$α$ Absorber [GA]

http://arxiv.org/abs/1703.03807


We report the discovery of massive $\log(M/M_\odot)=10.74^{+0.18}_{-0.16}$ galaxy at the same redshift as a carbon-monoxide bearing sub-damped Lyman $\alpha$ absorber (sub-DLA) seen in the spectrum of the QSO J1439+1117. The galaxy, J1439B, is located 4.7″ from the QSO sightline, a projected distance of 38 physical kpc at $z=2.4189$, and exhibits broad optical emission lines ($\sigma_{\rm{[O III]}}=303 \pm 12$ km s$^{-1}$) with ratios characteristic of excitation by an active galactic nucleus (AGN). The galaxy has a factor of $\sim$10 lower star formation than is typical of star-forming galaxies of the same mass and redshift. The nearby DLA is highly enriched, suggesting its galactic counterpart must be massive if it follows the $z\sim2$ mass-metallicity relationship. Metallic absorption associated with the DLA is spread over a velocity range $\Delta v > 1000$ km s$^{-1}$, suggesting an energetic origin. We explore the possibility that a different galaxy could be responsible for the rare absorber, and conclude it is unlikely based on imaging, integral field spectroscopy, and high-$z$ massive galaxy pair statistics. We argue that the gas seen in absorption against the QSO was likely ejected from the galaxy J1439B and therefore provides a unique observational probe of AGN feedback in the distant universe.

Read this paper on arXiv…

G. Rudie, A. Newman and M. Murphy
Tue, 14 Mar 17
10/74

Comments: 14 pages, 9 figures, to be submitted to ApJ

Massive Fields as Systematics for Single Field Inflation [CEA]

http://arxiv.org/abs/1703.04477


During inflation, massive fields can contribute to the power spectrum of curvature perturbation via a dimension-5 operator. This contribution can be considered as a bias for the program of using $n_s$ and $r$ to select inflation models. Even the dimension-5 operator is suppressed by $\Lambda = M_p$, there is still a significant shift on the $n_s$-$r$ diagram if the massive fields have $m\sim H$. On the other hand, if the heavy degree of freedom appear only at the same energy scale as the suppression scale of the dimension-5 operator, then significant shift on the $n_s$-$r$ diagram takes place at $m=\Lambda \sim 70H$, which is around the inflationary time-translation symmetry breaking scale. Hence, the systematics from massive fields pose a greater challenge for future high precision experiments for inflationary model selection. This result can be thought of as the impact of UV sensitivity to inflationary observables.

Read this paper on arXiv…

H. Jiang and Y. Wang
Tue, 14 Mar 17
11/74

Comments: 11 pages, 3 figures

A dynamo mechanism as the potential origin of the long cycle in Double Periodic Variables [SSA]

http://arxiv.org/abs/1703.03876


The class of Double Period Variables (DPVs) consists of close interacting binaries, with a characteristic long period that is an order of magnitude longer than the corresponding orbital period, many of them with a characteristic ratio of about 3.5×10^1. We consider here the possibility that the accretion flow is modulated as a result of a magnetic dynamo cycle. Due to the short binary separations, we expect the rotation of the donor star to be synchronized with the rotation of the binary due to tidal locking. We here present a model to estimate the dynamo number and the resulting relation between the activity cycle length and the orbital period, as well as an estimate for the modulation of the mass transfer rate. The latter is based on Applegate’s scenario, implying cyclic changes in the radius of the donor star and thus in the mass transfer rate as a result of magnetic activity. Our model is applied to a sample of 17 systems with known physical parameters, 10 also with known orbital periods. In spite of the uncertainties of our simplified framework, the results show a reasonable agreement, indicating that a dynamo interpretation is potentially feasible. At the same time, we note that the orbital period variations resulting from Applegate’s model are sufficiently small to be consistent with the data. We conclude that both larger samples with known physical parameters as well as potential direct probes of the magnetism of the donor star, including cold spots as well as polarization, will be valuable to further constrain the nature of these systems.

Read this paper on arXiv…

D. Schleicher and R. Mennickent
Tue, 14 Mar 17
12/74

Comments: 10 pages, 2 tables, 1 figure, accepted for publication with A&A

Petrographic and geochemical evidence for multiphase formation of carbonates in the Martian orthopyroxenite Allan Hills 84001 [EPA]

http://arxiv.org/abs/1703.04432


Martian meteorites can provide valuable information about past environmental conditions on Mars. Allan Hills 84001 formed more than 4 Gyr ago, and owing to its age and long exposure to the Martian environment, this meteorite has features that may record early processes. These features include a highly fractured texture, gases trapped during one or more impact events or during formation of the rock, and spherical Fe-Mg-Ca carbonates. Here we have concentrated on providing new insights into the context of these carbonates using a range of techniques to explore whether they record multiple precipitation and shock events. The petrographic features and compositional properties of these carbonates indicate that at least two pulses of Mg- and Fe-rich solutions saturated the rock. Those two generations of carbonates can be distinguished by a very sharp change in compositions, from being rich in Mg and poor in Fe and Mn, to being poor in Mg and rich in Fe and Mn. Between these two generations of carbonate is evidence for fracturing and local corrosion.

Read this paper on arXiv…

C. Moyano-Cambero, J. Trigo-Rodriguez, M. Benito, et. al.
Tue, 14 Mar 17
13/74

Comments: 30 pages, 11 figures, and 3 tables, Meteoritics & Planetary Science (2017)

Global constraints on absolute neutrino masses and their ordering [CL]

http://arxiv.org/abs/1703.04471


Within the standard three-neutrino framework, the absolute neutrino masses and their ordering (either normal, NO, or inverted, IO) are currently unknown. However, the combination of current data coming from oscillation experiments, neutrinoless double beta decay searches, and cosmological surveys, can provide interesting constraints for such unknowns in the sub-eV mass range, down to O(0.1) eV in some cases. We discuss current limits on absolute neutrino mass observables by performing a global data analysis, that includes the latest results from oscillation experiments, neutrinoless double beta decay bounds from the KamLAND-Zen experiment, and constraints from representative combinations of Planck measurements and other cosmological data sets. In general, NO appears to be somewhat favored with respect to IO at the level of ~2 sigma, mainly by neutrino oscillation data (especially atmospheric), corroborated by cosmological data in some cases. Detailed constraints are obtained via the chi^2 method, by expanding the parameter space either around separate minima in NO and IO, or around the absolute minimum in any ordering. Implications for upcoming oscillation and non-oscillation neutrino experiments, including beta-decay searches, are also discussed.

Read this paper on arXiv…

F. Capozzi, E. Valentino, E. Lisi, et. al.
Tue, 14 Mar 17
14/74

Comments: 17 pages, including 3 tables and 11 figures

Non-LTE line formation of Fe in late-type stars IV: Modelling of the solar centre-to-limb variation in 3D [SSA]

http://arxiv.org/abs/1703.04027


Our ability to model the shapes and strengths of iron lines in the solar spectrum is a critical test of the accuracy of the solar iron abundance, which sets the absolute zero-point of all stellar metallicities. We use an extensive 463-level Fe atom with new photoionisation cross-sections for FeI as well as quantum mechanical calculations of collisional excitation and charge transfer with neutral hydrogen; the latter effectively remove a free parameter that has hampered all previous line formation studies of Fe in non-local thermodynamic equilibrium (NLTE). For the first time, we use realistic 3D NLTE calculations of Fe for a quantitative comparison to solar observations. We confront our theoretical line profiles with observations taken at different viewing angles across the solar disk with the Swedish 1-m Solar Telescope. We find that 3D modelling well reproduces the observed centre-to-limb behaviour of spectral lines overall, but highlight aspects that may require further work, especially cross-sections for inelastic collisions with electrons. Our inferred solar iron abundance is log(eps(Fe))=7.48+-0.04.

Read this paper on arXiv…

K. Lind, A. Amarsi, M. Asplund, et. al.
Tue, 14 Mar 17
15/74

Comments: 13 pages, 8 figures, accepted for publication in MNRAS

Isotope shift and search for metastable superheavy elements in astrophysical data [CL]

http://arxiv.org/abs/1703.04250


Spectral lines belonging to the short-lifetime heavy radioactive elements up to Es ($Z$=99) have been found in the spectra of the Przybylski’s star. We suggest that these unstable elements may be decay products of a “magic” metastable nucleus belonging to the the island of stability where the nuclei have a magic number of neutrons $N=184$. The laboratory-produced nuclei have a significantly smaller number of neutrons. To identify spectra of the $N=184$ isotopes of these nuclei and their neutron-reach superheavy decay products in astrophysical data we calculate the isotope shift which should be added to the laboratory – measured wavelenghs. The results for the isotopic shifts in the strongest optical electromagnetic transitions in No, Lr, Nh, Fl,and $Z$=120 elements are presented.

Read this paper on arXiv…

V. Dzuba, V. Flambaum and J. Webb
Tue, 14 Mar 17
16/74

Comments: 4 pages, no figures

Gain factor and parameter settings optimization of the new gamma-ray burst polarimeter POLAR [IMA]

http://arxiv.org/abs/1703.04210


As a space-borne detector POLAR is designed to conduct hard X-ray polarization measurements of gamma-ray bursts on the statistically significant sample of events and with an unprecedented accuracy. During its development phase a number of tests, calibrations runs and verification measurements were carried out in order to validate instrument functionality and optimize operational parameters. In this article we present results on gain optimization togeter with verification data obtained in the course of broad laboratory and environmental tests. In particular we focus on exposures to the $^{137}$Cs radioactive source and determination of the gain dependence on the high voltage for all 1600 detection channels of the polarimeter. Performance of the instrument is described in detail with respect to the dynamic range, energy resolution and temperature dependence. Gain optimization algorithms and response non-uniformity studies are also broadly discussed. Results presented below constitute important parts for development of the POLAR calibration and operation database.

Read this paper on arXiv…

X. Zhang, W. Hajdas, H. Xiao, et. al.
Tue, 14 Mar 17
17/74

Comments: 22 pages, 14 figures

Little Bear's Pulsating Stars: Variable Star Census of dSph UMi Galaxy [SSA]

http://arxiv.org/abs/1703.04258


Recent observations and a photometric search for variable stars in the Ursa Minor dwarf spheroidal galaxy (UMi dSph) are presented. Our observations were taken at Apache Point Observatory in 2014 and 2016 using the 0.5m ARCSAT telescope and the West Mountain Observatory 0.9m telescope of Brigham Young University in 2016. Previously known RR Lyrae stars in our field of view of the UMi dSph are identified, and we also catalog new variable star candidates. Tentative classifications are given for some of the new variable stars. We have conducted period searches with the data collected with the WMO telescope. Our ultimate goal is to create an updated catalog of variable stars in the UMi dSph and to compare the RR Lyrae stellar characteristics to other RR Lyrae stars found in the Local Group dSph galaxies.

Read this paper on arXiv…

K. Kinemuchi, E. Jeffery, C. Kuehn, et. al.
Tue, 14 Mar 17
18/74

Comments: 3 pages, proceedings of the 22nd Los Alamos Stellar Pulsation Conference: “Wide-Field Variability Surveys: a 21st-century Perspective”, to be published in EPJ WOC

LSPM J1314: An oversized magnetic star with constraints on the radio emission mechanism [SSA]

http://arxiv.org/abs/1703.04488


LSPM J1314+1320 (=NLTT 33370) is a binary star system consisting of two nearly identical pre-main sequence stars of spectral type M7. The system is remarkable among ultracool dwarfs for being the most luminous radio emitter over the widest frequency range. Masses and luminosities are at first sight consistent with the system being coeval at age ~80 Myr according to standard (non-magnetic) evolutionary models. However, these models predict an average effective temperature, 2950 +/- 5 K, which is 180 K hotter than the empirical value. Thus, the empirical radii are oversized relative to the standard models by ~13%. We demonstrate that magnetic stellar models can account quantitatively for the oversizing. As a check on our models, we note that the radio emission limits the surface magnetic field strengths: the limits depend on identifying the radio emission mechanism. We find that the field strengths required by our magnetic models are too strong to be consistent with gyrosynchrotron emission, but are consistent with electron cyclotron maser emission.

Read this paper on arXiv…

J. MacDonald and D. Mullan
Tue, 14 Mar 17
19/74

Comments: Submitted to the Astrophysical Journal

Filamentary fragmentation in a turbulent medium [GA]

http://arxiv.org/abs/1703.04473


We present the results of smoothed particle hydrodynamic simulations investigating the evolution and fragmentation of filaments that are accreting from a turbulent medium. We show that the presence of turbulence, and the resulting inhomogeneities in the accretion flow, play a significant role in the fragmentation process. Filaments which experience a weakly turbulent accretion flow fragment in a two-tier hierarchical fashion, similar to the fragmentation pattern seen in the Orion Integral Shaped Filament. Increasing the energy in the turbulent velocity field results in more sub-structure within the filaments, and one sees a shift from gravity-dominated fragmentation to turbulence-dominated fragmentation. The sub-structure formed in the filaments is elongated and roughly parallel to the longitudinal axis of the filament, similar to the fibres seen in observations of Taurus, and suggests that the fray and fragment scenario is a possible mechanism for the production of fibres. We show that the formation of these fibre-like structures is linked to the vorticity of the velocity field inside the filament and the filament’s accretion from an inhomogeneous medium. Moreover, we find that accretion is able to drive and sustain roughly sonic levels of turbulence inside the filaments, but is not able to prevent radial collapse once the filaments become supercritical. However, the supercritical filaments which contain fibre-like structures do not collapse radially, suggesting that fibrous filaments may not necessarily become radially unstable once they reach the critical line-density.

Read this paper on arXiv…

S. Clarke, A. Whitworth, A. Duarte-Cabral, et. al.
Tue, 14 Mar 17
20/74

Comments: (Accepted for publication in MNRAS)

First Detection of Mid-Infrared Variability from an Ultraluminous X-Ray Source Holmberg II X-1 [HEAP]

http://arxiv.org/abs/1703.03802


We present mid-infrared (IR) light curves of the Ultraluminous X-ray Source (ULX) Holmberg II X-1 from observations taken between 2014 January 13 and 2017 January 5 with the \textit{Spitzer Space Telescope} at 3.6 and 4.5 $\mu$m in the \textit{Spitzer} Infrared Intensive Transients Survey (SPIRITS). The mid-IR light curves, which reveal the first detection of mid-IR variability from a ULX, is determined to arise primarily from dust emission rather than from a jet or an accretion disk outflow. We derived the evolution of the dust temperature ($T_\mathrm{d}\sim600 – 800$ K), IR luminosity ($L_\mathrm{IR}\sim3\times10^4$ $\mathrm{L}_\odot$), mass ($M_\mathrm{d}\sim1-3\times10^{-6}$ $\mathrm{M}_\odot$), and equilibrium temperature radius ($R_\mathrm{eq}\sim10-20$ AU). A comparison of X-1 with a sample spectroscopically identified massive stars in the Large Magellanic Cloud on a mid-IR color-magnitude diagram suggests that the mass donor in X-1 is a supergiant (sg) B[e]-star. The sgB[e]-interpretation is consistent with the derived dust properties and the presence of the [Fe II] ($\lambda=1.644$ $\mu$m) emission line revealed from previous near-IR studies of X-1. We attribute the mid-IR variability of X-1 to increased heating of dust located in a circumbinary torus. It is unclear what physical processes are responsible for the increased dust heating; however, it does not appear to be associated with the X-ray flux from the ULX given the constant X-ray luminosities provided by serendipitous, near-contemporaneous X-ray observations around the first mid-IR variability event in 2014. Our results highlight the importance of mid-IR observations of luminous X-ray sources traditionally studied at X-ray and radio wavelengths.

Read this paper on arXiv…

R. Lau, M. Heida, M. Kasliwal, et. al.
Tue, 14 Mar 17
21/74

Comments: 9 page, 4 figures, 1 table, Accepted to ApJ Letters

Double O-Ne-Mg white dwarfs merging as the source of the Powerfull Gravitational Waves for LIGO/VIRGO type interferometers [HEAP]

http://arxiv.org/abs/1703.04000


New strong non spiralling gravitational waves (GW) source for LIGO/VIRGO detectors are proposed. It is noted that double O-Ne-Mg white dwarfs mergers can produce strong gravitational waves with frequencies in the 600-1200 Hz range. Such events can be followed by the Super Nova type Ia.

Read this paper on arXiv…

V. Lipunov
Tue, 14 Mar 17
22/74

Comments: 4 pages, submitted to New Astronomy

On the Absence of Non-thermal X-ray emission around Runaway O stars [HEAP]

http://arxiv.org/abs/1703.04059


Theoretical models predict that the compressed interstellar medium around runaway O stars can produce high-energy non-thermal diffuse emission, in particular, non-thermal X-ray and $\gamma$-ray emission. So far, detection of non-thermal X-ray emission was claimed for only one runaway star AE Aur. We present a search for non-thermal diffuse X-ray emission from bow shocks using archived XMM-Newton observations for a clean sample of 6 well-determined runaway O stars. We find that none of these objects present diffuse X-ray emission associated to their bow shocks, similarly to previous X-ray studies toward $\zeta$ Oph and BD$+$43$^{\circ}$3654. We carefully investigated multi-wavelength observations of AE Aur and could not confirm previous findings of non-thermal X-rays. We conclude that so far there is no clear evidence of non-thermal extended emission in bow shocks around runaway O stars.

Read this paper on arXiv…

J. Toala, L. Oskinova and R. Ignace
Tue, 14 Mar 17
23/74

Comments: 6 pages, 2 tables, 3 figures; Accepted to ApJ Letters

Cosmological Implications of Nonlocal Gravity [CL]

http://arxiv.org/abs/1703.04205


We present extensions of the treatment contained in our recent paper on nonlocal Newtonian cosmology [C. Chicone and B. Mashhoon, J. Math. Phys. 57, 072501 (2016)]. That is, the implications of the recent nonlocal generalization of Einstein’s theory of gravitation are further investigated within the regime of Newtonian cosmology. In particular, we treat the nonlocal problem of structure formation for a spherically symmetric expanding dust model and show numerically that as the central density contrast grows, it tends to decrease slowly with radial distance as the universe expands. The nonlocal violation of Newton’s shell theorem provides a physical interpretation of our numerical results.

Read this paper on arXiv…

C. Chicone and B. Mashhoon
Tue, 14 Mar 17
24/74

Comments: 51 pages, 6 figures. Dedicated to Friedrich W. Hehl in honor of his 80th birthday

Classical collapse to black holes and white hole quantum bounces: A review [CL]

http://arxiv.org/abs/1703.04138


In the last four decades different programs have been carried out aiming at understanding the final fate of gravitational collapse of massive bodies once some prescriptions for the behaviour of gravity in the strong field regime are provided. The general picture arising from most of these scenarios is that the classical singularity at the end of collapse is replaced by a bounce. The most striking consequence of the bounce is that the black hole horizon may live for only a finite time. The possible implications for astrophysics are important since, if these models capture the essence of the collapse of a massive star, an observable signature of quantum gravity may be hiding in astrophysical phenomena. One intriguing idea that is implied by these models is the possible existence of exotic compact objects, of high density and finite size, that may not be covered by an horizon. The present article outlines the main features of these collapse models and some of the most relevant open problems. The aim is to provide a comprehensive (as much as possible) overview of the current status of the field from the point of view of astrophysics. As a little extra, a new toy model for collapse leading to the formation of a quasi static compact object is presented.

Read this paper on arXiv…

D. Malafarina
Tue, 14 Mar 17
25/74

Comments: 29 pages, 8 figures, comments are welcome

Synthetic streams in a Gravitational Wave inspiral search with a multi-detector network [CL]

http://arxiv.org/abs/1401.7967


Gravitational Wave Inspiral search with a global network of interferometers when carried in a phase coherent fashion would mimic an effective multi-detector network with synthetic streams constructed by the linear combination of the data from different detectors. For the first time, we demonstrate that the two synthetic data streams pertaining to the two polarizations of Gravitational Wave can be derived prior to the maximum-likelihood analysis in a most natural way using the technique of singular-value-decomposition applied to the network signal-to-noise ratio vector. We construct the network matched filters in combined network plus spectral space which capture both the synthetic streams. We further show that the network LLR is then sum of the LLR of each synthetic stream. The four extrinsic parameters are mapped to the two amplitudes and two phases. The maximization over these is a straightforward approach closely linked to the single detector approach. Towards the end, we connect all the previous works related to the multi-detector Gravitational Wave inspiral search and express in the same notation in order to bring under the same footing.

Read this paper on arXiv…

K. Haris and A. Pai
Tue, 14 Mar 17
26/74

Comments: LIGO laboratory document number: LIGO-P1300229

Mass function of galaxy clusters in relativistic inhomogeneous cosmology [CEA]

http://arxiv.org/abs/1703.04189


The current cosmological model ($\Lambda$CDM) with the underlying FLRW metric relies on the assumption of local isotropy, hence homogeneity of the Universe. Difficulties arise when one attempts to justify this model as an average description of the Universe from first principles of general relativity, since in general, the Einstein tensor built from the averaged metric is not equal to the averaged stress–energy tensor. In this context, the discrepancy between these quantities is called “cosmological backreaction” and has been the subject of scientific debate among cosmologists and relativists for more than $20$ years. Here we present one of the methods to tackle this problem, i.e. averaging the scalar parts of the Einstein equations, together with its application, the cosmological mass function of galaxy clusters.

Read this paper on arXiv…

J. Ostrowski, T. Buchert and B. Roukema
Tue, 14 Mar 17
27/74

Comments: 4 pages, 1 figure

The Gibbs paradox, the Landauer principle and the irreversibility associated with tilted observers [CL]

http://arxiv.org/abs/1703.03958


It is well known that, in the context of General Relativity, some spacetimes, when described by a congruence of comoving observers, may consist in a distribution of a perfect (non-dissipative) fluid, whereas the same spacetime as seen by a “tilted”‘ (Lorentz-boosted) congruence of observers, may exhibit the presence of dissipative processes. As we shall see, the appearence of entropy producing processes are related to the tight dependence of entropy on the specific congruence of observers. This fact is well illustrated by the Gibbs paradox. The appearance of such dissipative processes, as required by the Landauer principle, are necessary, in order to erase the different amount of information stored by comoving observers, with respect to tilted ones.

Read this paper on arXiv…

L. Herrera
Tue, 14 Mar 17
28/74

Comments: 10 pages Latex. Invited contribution for the special issue “Advances in Relativistic Statistical Mechanics” published in Entropy

Strongly baryon-dominated disk galaxies at the peak of galaxy formation ten billion years ago [GA]

http://arxiv.org/abs/1703.04310


In cold dark matter cosmology, the baryonic components of galaxies are thought to be mixed with and embedded in non-baryonic and non-relativistic dark matter, which dominates the total mass of the galaxy and its dark matter halo. In the local Universe, the mass of dark matter within a galactic disk increases with disk radius, becoming appreciable and then dominant in the outer, baryonic regions of the disks of star-forming galaxies. This results in rotation velocities of the visible matter within the disk that are constant or increasing with disk radius. Comparison between the dynamical mass and the sum of stellar and cold gas mass at the peak epoch of galaxy formation, inferred from ancillary data, suggest high baryon factions in the inner, star-forming regions of the disks. Although this implied baryon fraction may be larger than in the local Universe, the systematic uncertainties (stellar initial mass function, calibration of gas masses) render such comparisons inconclusive in terms of the mass of dark matter. Here we report rotation curves for the outer disks of six massive star-forming galaxies, and find that the rotation velocities are not constant, but decrease with radius. We propose that this trend arises because of two main factors: first, a large fraction of the massive, high-redshift galaxy population was strongly baryon dominated, with dark matter playing a smaller part than in the local Universe; and second, the large velocity dispersion in high-redshift disks introduces a substantial pressure term that leads to a decrease in rotation velocity with increasing radius. The effect of both factors appears to increase with redshift. Qualitatively, the observations suggest that baryons in the early Universe efficiently condensed at the centres of dark matter halos when gas fractions were high, and dark matter was less concentrated. [Abridged]

Read this paper on arXiv…

R. Genzel, N. Schreiber, H. Ubler, et. al.
Tue, 14 Mar 17
29/74

Comments: Accepted for publication in Nature. Note press embargo until 1800 London time / 1400 US Eastern Time on 15 March 2017

Is the cosmological dark sector better modeled by a generalized Chaplygin gas or by a scalar field? [CEA]

http://arxiv.org/abs/1703.04149


Both scalar fields and (generalized) Chaplygin gases have been widely used separately to characterize the dark sector of the Universe. Here we investigate the cosmological background dynamics for a mixture of both these components and quantify the fractional abundances that are admitted by observational data from supernovae of type Ia and from the evolution of the Hubble rate.

Read this paper on arXiv…

S. Campo, J. Fabris, R. Herrera, et. al.
Tue, 14 Mar 17
30/74

Comments: 15 pages, 5 figures

Discovery of Extreme [OIII]+H$β$ Emitting Galaxies Tracing an Overdensity at z~3.5 in CDF-South [GA]

http://arxiv.org/abs/1703.03814


Using deep multi-wavelength photometry of galaxies from ZFOURGE, we group galaxies at $2.5<z<4.0$ by the shape of their spectral energy distributions (SEDs). We identify a population of galaxies with excess emission in the $K_s$-band, which corresponds to [OIII]+H$\beta$ emission at $2.95<z<3.65$. This population includes 78% of the bluest galaxies with UV slopes steeper than $\beta = -2$. We de-redshift and scale this photometry to build two composite SEDs, enabling us to measure equivalent widths of these Extreme [OIII]+H$\beta$ Emission Line Galaxies (EELGs) at $z\sim3.5$. We identify 60 galaxies that comprise a composite SED with [OIII]+H$\beta$ rest-frame equivalent width of $803\pm228$\AA\ and another 218 galaxies in a composite SED with equivalent width of $230\pm90$\AA. These EELGs are analogous to the `green peas’ found in the SDSS, and are thought to be undergoing their first burst of star formation due to their blue colors ($\beta < -1.6$), young ages ($\log(\rm{age}/yr)\sim7.2$), and low dust attenuation values. Their strong nebular emission lines and compact sizes (typically $\sim1.4$ kpc) are consistent with the properties of the star-forming galaxies possibly responsible for reionizing the universe at $z>6$. Many of the EELGs also exhibit Lyman-$\alpha$ emission. Additionally, we find that many of these sources are clustered in an overdensity in the Chandra Deep Field South, with five spectroscopically confirmed members at $z=3.474 \pm 0.004$. The spatial distribution and photometric redshifts of the ZFOURGE population further confirm the overdensity highlighted by the EELGs.

Read this paper on arXiv…

B. Forrest, K. Tran, A. Broussard, et. al.
Tue, 14 Mar 17
31/74

Comments: Accepted for publication in ApJL. 8 pages, 4 figures

Probing the Extragalactic Cosmic Rays origin with gamma-ray and neutrino backgrounds [HEAP]

http://arxiv.org/abs/1703.04158


The GeV-TeV gamma-rays and the PeV-EeV neutrino backgrounds provide a unique window on the nature of the ultra-high-energy cosmic-ray (UHECR). We discuss the implications of the recent Fermi-LAT data regarding the extragalactic gamma-ray background (EGB) and related estimates of the contribution of point sources as well as IceCube neutrino data on the origin of the ultra-high-energy cosmic-ray (UHECR). We calculate the diffuse flux of cosmogenic $\gamma$-rays and neutrinos produced by the UHECRs and derive constraints on the possible cosmological evolution of UHECR sources. In particular, we show that the mixed-composition scenario considered in \citet{Globus2015b}, that is in agreement with both (i) Auger measurements of the energy spectrum and composition up to the highest energies and (ii) the ankle-like feature in the light component detected by KASCADE-Grande, is compatible with both the Fermi-LAT measurements and with current IceCube limits. We also discuss the possibility for future experiments to detect associated cosmogenic neutrinos and further constrain the UHECR models, including possible subdominant UHECR proton sources.

Read this paper on arXiv…

N. Globus, D. Allard, E. Parizot, et. al.
Tue, 14 Mar 17
32/74

Comments: 6 pages, 4 figures, submitted to ApJ Letters

Excitation of turbulence in accretion disks of binary stars by non-linear perturbations [SSA]

http://arxiv.org/abs/1703.04304


Accretion disks in binary systems can experience hydrodynamic impact at inner as well as outer edges. The first case is typical for protoplanetary disks around young T Tau stars. The second one is typical for circumstellar disks in close binaries. As a result of such an impact, perturbations with different scales and amplitudes are excited in the disk. We investigated the nonlinear evolution of perturbations of a finite, but small amplitude, at the background of sub-Keplerian flow. Nonlinear effects at the front of perturbations lead to the formation of a shock wave, namely the discontinuity of the density and radial velocity. At this, the tangential flow in the neighborhood of the shock becomes equivalent to the flow in in the boundary layer. Instability of the tangential flow further leads to turbulization of the disk. Characteristics of the turbulence depend on perturbation parameters, but alpha-parameter of Shakura-Sunyaev does not exceed ~0.1.

Read this paper on arXiv…

E. Kurbatov and D. Bisikalo
Tue, 14 Mar 17
33/74

Comments: Accepted in Astronomy Reports

Stable accretion from a cold disc in highly magnetized neutron stars [HEAP]

http://arxiv.org/abs/1703.04528


The aim of this paper is to investigate the transition of a strongly magnetized neutron star into the accretion regime with very low accretion rate. For this purpose we monitored the Be-transient X-ray pulsar GRO J1008-57 throughout a full orbital cycle. The current observational campaign was performed with the Swift/XRT telescope in the soft X-ray band (0.5-10 keV) between two subsequent Type I outbursts in January and September 2016. The expected transition to the propeller regime was not observed. However, the transitions between different regimes of accretion were detected. In particular, after an outburst the source entered a stable accretion state characterised by the accretion rate of ~10^14-10^15 g/s. We associate this state with accretion from a cold (non-ionised) disc of temperature below ~6500 K. We argue that a transition to such accretion regime should be observed in all X-ray pulsars with certain combination of the rotation frequency and magnetic field strength. Moreover, the propeller effect should never be observed in such sources even for very low mass accretion rates. The proposed model of accretion from a cold disc is able to explain several puzzling observational properties of X-ray pulsars.

Read this paper on arXiv…

S. Tsygankov, A. Mushtukov, V. Suleimanov, et. al.
Tue, 14 Mar 17
34/74

Comments: 10 pages, 4 figures, 1 table, submitted to A&A

A terrestrial-sized exoplanet at the snow line of TRAPPIST-1 [EPA]

http://arxiv.org/abs/1703.04166


The TRAPPIST-1 system is the first transiting planet system found orbiting an ultra-cool dwarf star. At least seven planets similar to Earth in radius and in mass were previously found to transit this host star. Subsequently, TRAPPIST-1 was observed as part of the K2 mission and, with these new data, we report the measurement of an 18.764 d orbital period for the outermost planet, TRAPPIST-1h, which was unconstrained until now. This value matches our theoretical expectations based on Laplace relations and places TRAPPIST-1h as the seventh member of a complex chain, with three-body resonances linking every member. We find that TRAPPIST-1h has a radius of 0.715 Earth radii and an equilibrium temperature of 169 K, placing it at the snow line. We have also measured the rotational period of the star at 3.3 d and detected a number of flares consistent with an active, middle-aged, late M dwarf.

Read this paper on arXiv…

R. Luger, M. Sestovic, E. Kruse, et. al.
Tue, 14 Mar 17
35/74

Comments: 36 pages, 8 figure, 2 tables. Submitted to Nat. Astron. on 3/10/2017

Novae: I. The maximum magnitude relation with decline time (MMRD) and distance [HEAP]

http://arxiv.org/abs/1703.04087


The origin and calibration of the maximum absolute magnitude relation with decline time (MMRD) for novae, first derived by Zwicky (1936) empirically validated by McLaughlin (1940) and widely used to estimate distances to classical novae and the near-constancy of the absolute magnitude of novae, 15 days after optical maximum, suggested by Buscombe and de Vaucouleurs (1955) are revisited in this paper and found to be valid. The main results presented in the paper are: (1) A physical derivation of the MMRD based on instantaneous injection of energy to the nova system. (2) A significantly better-constrained MMRD: M_{V,0} = 2.16(+-0.16)log_{10}t_2 – 10.804(+-0.117) using a two step calibration procedure. (3) It is shown that the MMRD is one of the best distance estimators to novae available to us and that accuracy of the distances is predominantly limited by an underestimated peak apparent brightness. (4) It is shown that the same MMRD calibration is applicable to novae of all speed class and to both Galactic and extragalactic novae. (5) It is shown that the absolute magnitudes of novae with 2.4 < t_2 < 86$days have a smaller scatter on day 12 (M_{V,12} = -6.616 +-0.043) compared to day 15 following optical maximum.
We reiterate the need for homogenised high fidelity spectrophotometric data in optical bands on classical and recurrent novae in outburst to effectively utilise the potential of the MMRD and M_{V,12} in determining their luminosities and distances.

Read this paper on arXiv…

N. Kantharia
Tue, 14 Mar 17
36/74

Comments: 25 pages

On the formation of the first quasars [GA]

http://arxiv.org/abs/1703.03808


Observations of the most luminous quasars at redshift z>6 reveal the existence of numerous supermasssive black holes (>10^9 Msun) already in place about twelve billion years ago. In addition, the interstellar medium of the galaxies hosting these black holes are observed to be chemically mature systems, with metallicities (Z>Zsun) and dust masses (>10^8 Msun) similar to that of more evolved, local galaxies. The connection between the rapid growth of the first supermassive black holes and the fast chemical evolution of the host galaxy is one of the most puzzling issues for theoretical models. Here we review state-of-the-art theoretical models that focus on this problem with particular emphasis on the conditions that lead to the formation of quasar seeds and their subsequent evolution at z>6.

Read this paper on arXiv…

R. Valiante, B. Agarwal, M. Habouzit, et. al.
Tue, 14 Mar 17
37/74

Comments: To be published in PASA. Comments are welcome

Thermochemistry and vertical mixing in the tropospheres of Uranus and Neptune: How convection inhibition can affect the derivation of deep oxygen abundances [EPA]

http://arxiv.org/abs/1703.04358


Thermochemical models have been used in the past to constrain the deep oxygen abundance in the gas and ice giant planets from tropospheric CO spectroscopic measurements. Knowing the oxygen abundance of these planets is a key to better understand their formation. These models have widely used dry and/or moist adiabats to extrapolate temperatures from the measured values in the upper troposphere down to the level where the thermochemical equilibrium between H$_2$O and CO is established. The mean molecular mass gradient produced by the condensation of H$_2$O stabilizes the atmosphere against convection and results in a vertical thermal profile and H$_2$O distribution that departs significantly from previous estimates. We revisit O/H estimates using an atmospheric structure that accounts for the inhibition of the convection by condensation. We use a thermochemical network and the latest observations of CO in Uranus and Neptune to calculate the internal oxygen enrichment required to satisfy both these new estimates of the thermal profile and the observations. We also present the current limitations of such modeling.

Read this paper on arXiv…

T. Cavalie, O. Venot, F. Selsis, et. al.
Tue, 14 Mar 17
38/74

Comments: 33 pages, 11 figures, accepted for publication in Icarus (2017)

The SNR Puppis A Revisited with Seven Years of Fermi Large Area Telescope Observations [HEAP]

http://arxiv.org/abs/1703.03911


Puppis A is a very famous and extensively studied supernova remnant (SNR) that shows strong evidence of shock-cloud interaction. We re-analyze the GeV $\gamma$-ray emission of it using seven years Pass 8 data recorded by the Fermi Large Area Telescope (Fermi-LAT). The morphology of the $\gamma$-ray emission is more compatible with that of the thermal X-ray and IR emissions than the radio image, which suggests a possible correlation between the gamma-ray emitting region and dense clouds. The $\gamma$-ray spectrum in the energy range of 1-500 GeV shows a break at $7.92\pm1.91$ GeV with the photon indices of $1.81\pm0.08$ below the break and $2.53\pm0.12$ above the break, which can naturally explain the lack of TeV $\gamma$-ray emission from Puppis A. The multi-wavelength observations favor a hadronic origin for the $\gamma$-ray emission.

Read this paper on arXiv…

Y. Xin, X. Guo, N. Liao, et. al.
Tue, 14 Mar 17
39/74

Comments: 9 pages, 3 figures, 4 tables, submitted to ApJ, comments are welcome

Light curve and SED modeling of the gamma-ray binary 1FGL J1018.6$-$5856: constraints on the orbital geometry and relativistic flow [HEAP]

http://arxiv.org/abs/1703.04214


We present broadband spectral energy distributions (SEDs) and light curves of the gamma-ray binary 1FGL J1018.6$-$5856 measured in the X-ray and the gamma-ray bands. We find that the orbital modulation in the low-energy gamma-ray band is similar to that in the X-ray band, suggesting a common spectral component. However, above a GeV the orbital light curve changes significantly. We suggest that the GeV band contains significant flux from a pulsar magnetosphere, while the X-ray to TeV light curves are dominated by synchrotron and Compton emission from an intrabinary shock (IBS). We find that a simple one-zone model is inadequate to explain the IBS emission, but that beamed Synchrotron-self Compton radiation from adiabatically accelerated plasma in the shocked pulsar wind can reproduce the complex multiband light curves, including the variable X-ray spike coincident with the gamma-ray maximum. The model requires inclination $\sim$50$^\circ$ and orbital eccentricity $\sim$0.35, consistent with the limited constraints from existing optical observations. This picture motivates searches for pulsations from the energetic young pulsar powering the wind shock.

Read this paper on arXiv…

H. An and R. Romani
Tue, 14 Mar 17
40/74

Comments: 10 pages, 5 figures, accepted for publication in ApJ

Steep Decay of GRB X-ray Flares: the Result of Anisotropic Synchrotron Radiation [HEAP]

http://arxiv.org/abs/1703.03986


When an emitting spherical shell with a constant Lorentz factor turns off emission abruptly at some radius, its high-latitude emission would obey the relation of $\hat{\alpha}$ (the temporal index) = $2 + \hat{\beta}$ (the spectral index). However, this relation is violated by the X-ray fares in some gamma-ray bursts (GRBs), whose $\hat{\alpha}$ is much more steeper. We show that the synchrotron radiation should be anisotropic when the angular distribution of accelerated electrons has preferable orientation, and this anisotropy would naturally lead to the steeper decay for the high-latitude emission if the the intrinsic emission is limb-brightened. We use our simple toy model to reproduce the temporal and the spectral evolution of the X-ray flares. We show that our model can well interpret the steep decay of the X-ray flares in the three GRBs selected as example. Recent simulations on particle acceleration may support the specific anisotropic distribution of the electrons adopted in our work. Reversely, confirmation of the anisotropy in the radiation would give meaningful clues to the details of electron acceleration in the emitting region.

Read this paper on arXiv…

J. Geng, Y. Huang and Z. Dai
Tue, 14 Mar 17
41/74

Comments: 5 pages, 1 figure, comments are welcome

A new perspective on turbulent Galactic magnetic fields through comparison of linear polarisation decomposition techniques [GA]

http://arxiv.org/abs/1703.04469


We compare two rotationally invariant decomposition techniques on linear polarisation data: the spin-2 spherical harmonic decomposition in two opposite parities, the $E$- and $B$-mode, and the multiscale analysis of the gradient of linear polarisation, $|\nabla \mathbf{P}|$. We demonstrate that both decompositions have similar properties in the image domain and the spatial frequency domain. They can be used as complementary tools for turbulence analysis of interstellar magnetic fields in order to develop a better understanding of the origin of energy sources for the turbulence, the origin of peculiar magnetic field structures and their underlying physics. We also introduce a new quantity $|\nabla EB|$ based on the $E$- and $B$-modes and we show that in the intermediate and small scales limit $|\nabla EB| \simeq |\nabla \mathbf{P}|$. Analysis of the 2.3 GHz S-band Polarization All Sky Survey (S -PASS) shows many extended coherent filament-like features appearing as ‘double-jumps’ in the $|\nabla \mathbf{P}|$ map that are correlated with negative and positive filaments of $B$-type polarisation. These local asymmetries between the two polarisation types, $E$ and $B$, of the non-thermal Galactic synchrotron emission have an influence on the $E$- and $B$-mode power spectra analyses. The wavelet-based formalism of the polarisation gradient analysis allows us to locate the position of $E$- or $B$-mode features responsible for the local asymmetries between the two polarisation types. In analysed subregions, the perturbations of the magnetic field are trigged by star clusters associated with HII regions, the Orion-Eridanus superbubble and the North Polar Spur at low Galactic latitude.

Read this paper on arXiv…

J. Robitaille, A. Scaife, E. Carretti, et. al.
Tue, 14 Mar 17
42/74

Comments: Accepted for publication on MNRAS (2017 March 10), 20 pages, 14 figures

A search for water maser emission from brown dwarfs and low-luminosity young stellar objects [SSA]

http://arxiv.org/abs/1703.04323


We present a survey for water maser emission toward a sample of 44 low-luminosity young objects, comprising (proto-)brown dwarfs, first hydrostatic cores (FHCs), and other young stellar objects (YSOs) with bolometric luminosities lower than 0.4 L$_\odot$. Water maser emission is a good tracer of energetic processes, such as mass-loss and/or accretion, and is a useful tool to study this processes with very high angular resolution. This type of emission has been confirmed in objects with L$_{\rm bol}\ge 1$ L$_\odot$. Objects with lower luminosities also undergo mass-loss and accretion, and thus, are prospective sites of maser emission. Our sensitive single-dish observations provided a single detection when pointing toward the FHC L1448 IRS 2E. However, follow-up interferometric observations showed water maser emission associated with the nearby YSO L1448 IRS 2 { (a Class 0 protostar of L$_{\rm bol}\simeq 3.6-5.3$ L$_\odot$)}, and did not find any emission toward L1448 IRS 2E. The upper limits for water maser emission determined by our observations are one order of magnitude lower than expected from the correlation between water maser luminosities and bolometric luminosities found for YSOs. This suggests that this correlation does not hold at the lower end of the (sub)stellar mass spectrum. Possible reasons are that the slope of this correlation is steeper at L$_{\rm bol}\le 1$ L$_\odot$, or that there is an absolute luminosity threshold below which water maser emission cannot be produced. Alternatively, if the correlation still stands at low luminosity, the detection rates of masers would be significantly lower than the values obtained in higher-luminosity Class 0 protostars.

Read this paper on arXiv…

J. Gomez, A. Palau, L. Uscanga, et. al.
Tue, 14 Mar 17
43/74

Comments: To be published in The Astronomical Journal. Eleven pages, four figures

SDSS IV MaNGA – Metallicity and nitrogen abundance gradients in local galaxies [GA]

http://arxiv.org/abs/1703.03813


We study the gas phase metallicity (O/H) and nitrogen abundance gradients traced by star forming regions in a representative sample of 550 nearby galaxies in the stellar mass range $\rm 10^9-10^{11.5} M_\odot$ with resolved spectroscopic data from the SDSS-IV MaNGA survey. Using strong-line ratio diagnostics (R23 and O3N2 for metallicity and N2O2 for N/O) and referencing to the effective (half-light) radius ($\rm R_e$), we find that the metallicity gradient steepens with stellar mass, lying roughly flat among galaxies with $\rm log(M_\star/M_\odot) = 9.0$ but exhibiting slopes as steep as -0.14 dex $\rm R_e^{-1}$ at $\rm log(M_\star/M_\odot) = 10.5$ (using R23, but equivalent results are obtained using O3N2). At higher masses, these slopes remain typical in the outer regions of our sample ($\rm R > 1.5 ~R_e$), but a flattening is observed in the central regions ($\rm R < 1~ R_e$). In the outer regions ($\rm R > 2.0 ~R_e$) we detect a mild flattening of the metallicity gradient in stacked profiles, although with low significance. The N/O ratio gradient provides complementary constraints on the average chemical enrichment history. Unlike the oxygen abundance, the average N/O profiles do not flatten out in the central regions of massive galaxies. The metallicity and N/O profiles both depart significantly from an exponential form, suggesting a disconnect between chemical enrichment and stellar mass surface density on local scales. In the context of inside-out growth of discs, our findings suggest that central regions of massive galaxies today have evolved to an equilibrium metallicity, while the nitrogen abundance continues to increase as a consequence of delayed secondary nucleosynthetic production.

Read this paper on arXiv…

F. Belfiore, R. Maiolino, C. Tremonti, et. al.
Tue, 14 Mar 17
44/74

Comments: resubmitted to MNRAS after replying to the referee’s comments

Design and experimental test of an optical vortex coronagraph [IMA]

http://arxiv.org/abs/1703.04228


The optical vortex coronagraph (OVC) is one of the promising ways for direct imaging exoplanets because of its small inner working angle and high throughput. This paper presents the design and laboratory demonstration performance at 633nm and 1520nm of the OVC based on liquid crystal polymers (LCP). Two LCPs has been manufactured in partnership with a commercial vendor. The OVC can deliver a good performance in laboratory test and achieve the contrast of the order 10^-6 at angular distance 3{\lambda}/D, which is able to image the giant exoplanets at a young stage in combination with extreme adaptive optics.

Read this paper on arXiv…

C. Liu, D. Ren, Y. Zhu, et. al.
Tue, 14 Mar 17
45/74

Comments: 8 pages and 6 figures

The Yale-Potsdam Stellar Isochrones (YaPSI) [SSA]

http://arxiv.org/abs/1703.03975


We introduce the Yale-Potsdam Stellar Isochrones (YaPSI), a new grid of stellar evolution tracks and isochrones of solar-scaled composition. In an effort to improve the Yonsei-Yale database, special emphasis is placed on the construction of accurate low-mass models (Mstar < 0.6 Msun), and in particular of their mass-luminosity and mass-radius relations, both crucial in characterizing exoplanet-host stars and, in turn, their planetary systems. The YaPSI models cover the mass range 0.15 to 5.0 Msun, densely enough to permit detailed interpolation in mass, and the metallicity and helium abundance ranges [Fe/H] = -1.5 to +0.3, and Y = 0.25 to 0.37, specified independently of each other (i.e., no fixed Delta Y/Delta Z relation is assumed). The evolutionary tracks are calculated from the pre-main sequence up to the tip of the red giant branch. The isochrones, with ages between 1 Myr and 20 Gyr, provide UBVRI colors in the Johnson-Cousins system, and JHK colors in the homogeneized Bessell & Brett system, derived from two different semi-empirical Teff-color calibrations from the literature. We also provide utility codes, such as an isochrone interpolator in age, metallicity, and helium content, and an interface of the tracks with an open-source Monte Carlo Markov-Chain tool for the analysis of individual stars. Finally, we present comparisons of the YaPSI models with the best empirical mass- luminosity and mass-radius relations available to date, as well as isochrone fitting of well-studied ste

Read this paper on arXiv…

F. Spada, P. Demarque, Y. Kim, et. al.
Tue, 14 Mar 17
46/74

Comments: 17 pages, 14 figures; accepted for publication in the Astrophysical Journal

Surface Gravities for 228 M, L, and T Dwarfs in the NIRSPEC Brown Dwarf Spectroscopic Survey [SSA]

http://arxiv.org/abs/1703.03811


We combine 131 new medium-resolution (R~2000) J-band spectra of M, L, and T dwarfs from the Keck NIRSPEC Brown Dwarf Spectroscopic Survey (BDSS) with 97 previously published BDSS spectra to study surface-gravity-sensitive indices for 228 low-mass stars and brown dwarfs spanning spectral types M5-T9. Specifically, we use an established set of spectral indices to determine surface gravity classifications for all M6-L7 objects in our sample by measuring equivalent widths (EW) of the K I lines at 1.1692, 1.1778, 1.2529 um, and the 1.2 um FeHJ absorption index. Our results are consistent with previous surface gravity measurements, showing a distinct double peak – at ~L5 and T5 – in K I EW as a function of spectral type. We analyze K I EWs of 73 objects of known ages and find a linear trend between log(Age) and EW. From this relationship, we assign age ranges to the very low gravity, intermediate gravity, and field gravity designations for spectral types M6-L0. Interestingly, the ages probed by these designations remain broad, change with spectral type, and depend on the gravity sensitive index used. Gravity designations are useful indicators of the possibility of youth, but current datasets cannot be used to provide a precise age estimate.

Read this paper on arXiv…

E. Martin, G. Mace, I. McLean, et. al.
Tue, 14 Mar 17
47/74

Comments: 33 pages, 13 figures, ApJ in press

Rapid Formation of Massive Black Holes in close proximity to Embryonic Proto-Galaxies [GA]

http://arxiv.org/abs/1703.03805


The Direct Collapse Black Hole (DCBH) scenario provides a solution for forming the massive black holes powering bright quasars observed in the early Universe. A prerequisite for forming a DCBH is that the formation of (much less massive) Population III stars be avoided – this can be achieved by destroying H$_2$ via Lyman-Werner (LW) radiation (E$_{\rm{LW}}$ = 12.6 eV). We find that two conditions must be met in the proto-galaxy that will host the DCBH. First, prior star formation must be delayed; this can be achieved with a background LW flux of J$_{\rm BG} \gtrsim 100\ J_{21}$. Second, an intense burst of LW radiation from a neighbouring star-bursting proto-galaxy is required, just before the gas cloud undergoes gravitational collapse, to finally suppress star formation completely. We show here for the first time using high-resolution hydrodynamical simulations, including full radiative transfer, that this low-level background, combined with tight synchronisation and irradiation of a secondary proto-galaxy by a primary proto-galaxy, inevitably moves the secondary proto-galaxy onto the isothermal atomic cooling track, without the deleterious effects of either photo-evaporating the gas or polluting it by heavy elements. These, atomically cooled, massive proto-galaxies are expected to ultimately form a DCBH of mass $10^4 – 10^5 M_{\odot}$.

Read this paper on arXiv…

J. Regan, E. Visbal, J. Wise, et. al.
Tue, 14 Mar 17
48/74

Comments: Published in Nature Astronomy, March 13th 2017

From voids to filaments: environmental transformations of galaxies in the SDSS [GA]

http://arxiv.org/abs/1703.04338


We investigate the impact of filament and void environments on galaxies, looking for residual effects beyond the known relations with environment density. We quantified the host environment of galaxies as the distance to the spine of the nearest filament, and compared various galaxy properties within 12 bins of this distance. We considered galaxies up to 10 $h^{-1}$Mpc from filaments, i.e. deep inside voids. The filaments were defined by a point process (the Bisous model) from the Sloan Digital Sky Survey data release 10. In order to remove the dependence of galaxy properties on the environment density and redshift, we applied weighting to normalise the corresponding distributions of galaxy populations in each bin. After the normalisation with respect to environment density and redshift, several residual dependencies of galaxy properties still remain. Most notable is the trend of morphology transformations, resulting in a higher elliptical-to-spiral ratio while moving from voids towards filament spines, bringing along a corresponding increase in the $g-i$ colour index and a decrease in star formation rate. After separating elliptical and spiral subsamples, some of the colour index and star formation rate evolution still remains. The mentioned trends are characteristic only for galaxies brighter than about $M_{r} = -20$ mag. Unlike some other recent studies, we do not witness an increase in the galaxy stellar mass while approaching filaments. The detected transformations can be explained by an increase in the galaxy-galaxy merger rate and/or the cut-off of extragalactic gas supplies (starvation) near and inside filaments. Unlike voids, large-scale galaxy filaments are not a mere density enhancement, but have their own specific impact on the constituent galaxies, reducing the star formation rate and raising the chances of elliptical morphology also at a fixed environment density level.

Read this paper on arXiv…

T. Kuutma, A. Tamm and E. Tempel
Tue, 14 Mar 17
49/74

Comments: 4 pages, 3 figures, Astronomy & Astrophysics letters accepted

Impact of radiogenic heating on the formation conditions of comet 67P/Churyumov-Gerasimenko [EPA]

http://arxiv.org/abs/1703.04227


Because of the high fraction of refractory material present in comets, the heat produced by the radiogenic decay of elements such as aluminium and iron can be high enough to induce the loss of ultravolatile species such as nitrogen, argon or carbon monoxide during their accretion phase in the protosolar nebula. Here, we investigate how heat generated by the radioactive decay of 26Al and 60Fe influences the formation of comet 67P/Churyumov-Gerasimenko, as a function of its accretion time and size of parent body. We use an existing thermal evolution model that includes various phase transitions, heat transfer in the ice-dust matrix, and gas diffusion throughout the porous material, based on thermodynamic parameters derived from Rosetta observations. Two possibilities are considered: either, to account for its bilobate shape, 67P/Churyumov-Gerasimenko was assembled from two primordial ~2 kilometer-sized planetesimals, or it resulted from the disruption of a larger parent body with a size corresponding to that of comet Hale-Bopp (~70 km). To fully preserve its volatile content, we find that either 67P/Churyumov-Gerasimenko’s formation was delayed between ~2.2 and 7.7 Myr after that of Ca-Al-rich Inclusions in the protosolar nebula or the comet’s accretion phase took place over the entire time interval, depending on the primordial size of its parent body and the composition of the icy material considered. Our calculations suggest that the formation of 67P/Churyumov-Gerasimenko is consistent with both its accretion from primordial building blocks formed in the nebula or from debris issued from the disruption of a Hale-Bopp-like body.

Read this paper on arXiv…

O. Mousis, A. Drouard, P. Vernazza, et. al.
Tue, 14 Mar 17
50/74

Comments: Accepted for publication in The Astrophysical Journal Letters

Precision Cosmology from Future Time Delays of Lensed Gravitational Wave and Electromagnetic Signals [CEA]

http://arxiv.org/abs/1703.04151


The”standard-siren” approaches of gravitational wave cosmology appeal to the luminosity distance estimation from the GW observation which relies on the fine details of the waveform. We propose a new waveform independent strategy based on the systems where strongly lensed gravitational waves (GWs) and their electromagnetic (EM) counterparts can be detected simultaneously. With the images and redshifts observed in the EM domain combined with very precise measurements of time delays from lensed GW signals, we can achieve precise cosmography in the era of third-generation gravitational-wave detectors. In particular we demonstrate that the uncertainty of the Hubble constant $H_0$ determination from just $10$ such systems can decrease to $\sim0.4\%$ in a flat $\Lambda$CDM universe.

Read this paper on arXiv…

K. Liao, X. Fan, X. Ding, et. al.
Tue, 14 Mar 17
51/74

Comments: N/A

Canvas and Cosmos: Visual Art Techniques Applied to Astronomy Data [IMA]

http://arxiv.org/abs/1703.04183


Bold colour images from telescopes act as extraordinary ambassadors for research astronomers because they pique the public’s curiosity. But are they snapshots documenting physical reality? Or are we looking at artistic spacescapes created by digitally manipulating astronomy images? This paper provides a tour of how original black and white data, from all regimes of the electromagnetic spectrum, are converted into the colour images gracing popular magazines, numerous websites, and even clothing. The history and method of the technical construction of these images is outlined. However, the paper focuses on introducing the scientific reader to visual literacy (e.g.human perception) and techniques from art (e.g. composition, colour theory) since these techniques can produce not only striking but politically powerful public outreach images. When created by research astronomers, the cultures of science and visual art can be balanced and the image can illuminate scientific results sufficiently strongly that the images are also used in research publications. Included are reflections on how they could feedback into astronomy research endeavours and future forms of visualization as well as on the relevance of outreach images to visual art.

Read this paper on arXiv…

J. English
Tue, 14 Mar 17
52/74

Comments: This is the submitted version (and lacks a couple of references, has lower quality figures, etc). 51 pages, 26 images. The paper has been published in IJMPD. For images by the author see this https URL

Cosmic ray driven winds in the Galactic environment and the cosmic ray spectrum [HEAP]

http://arxiv.org/abs/1703.04490


Cosmic Rays escaping the Galaxy exert a force on the interstellar medium directed away from the Galactic disk. If this force is larger than the gravitational pull due to the mass embedded in the Galaxy, then galactic winds may be launched. Such outflows may have important implications for the history of star formation of the host galaxy, and in turn affect in a crucial way the transport of cosmic rays, both due to advection with the wind and to the excitation of waves by the same cosmic rays, through streaming instability. The possibility to launch cosmic ray induced winds and the properties of such winds depend on environmental conditions, such as the density and temperature of the plasma at the base of the wind and the gravitational potential, especially the one contributed by the dark matter halo. In this paper we make a critical assessment of the possibility to launch cosmic ray induced winds for a Milky-Way-like galaxy and how the properties of the wind depend upon the conditions at the base of the wind. Special attention is devoted to the implications of different conditions for wind launching on the spectrum of cosmic rays observed at different locations in the disc of the galaxy. We also comment on how cosmic ray induced winds compare with recent observations of Oxygen absorption lines in quasar spectra and emission lines from blank-sky, as measured by XMM-Newton/EPIC-MOS.

Read this paper on arXiv…

S. Recchia, P. Blasi and G. Morlino
Tue, 14 Mar 17
53/74

Comments: N/A

Features in single field slow-roll inflation [CEA]

http://arxiv.org/abs/1703.04375


We compare the effects of local features (LF) and branch features (BF) of the inflaton potential on the spectrum of primordial perturbations. We show that LF affect the spectrum in a narrow range of scales while BF produce a step between large and small scales with respect to the featureless spectrum. We comment on the possibility of distinguishing between these two types of feature models from the analysis of the Cosmic Microwave Background (CMB) radiation data.
We also show that there exists a quantitative similarity between the primordial spectra predicted by two of the BF potentials considered. This could lead to a degeneracy of their predicted CMB temperature spectra which could make difficult to discriminate between the models from a CMB analysis. We comment on the possibility that the degeneracy can be broken when higher order terms in the perturbations are considered. In this sense non-Gaussianity may play an important role in discerning between different inflationary models which predict similar spectra.

Read this paper on arXiv…

A. Cadavid
Tue, 14 Mar 17
54/74

Comments: To be published in Journal of Physics: Conference Series as the proceedings of the 70&70 Classical and Quantum Gravitation Party: Meeting with Two Latin American Masters on Theoretical Physics (Cartagena de Indias – Colombia, 28th-30th September, 2016)

On the Effectiveness of Multi-Instrument Solar Flare Observations During Solar Cycle 24 [SSA]

http://arxiv.org/abs/1703.04412


Our current fleet of space-based solar observatories offer us a wealth of opportunities to study solar flares over a range of wavelengths, and the greatest advances in our understanding of flare physics often come from coordinated observations between different instruments. However, despite considerable effort to coordinate this armada of instruments over the years (e.g. through the Max Millennium Program of Solar Flare Research), there are few solar flares that have been observed by most or all available instruments simultaneously, due to the combination of each instrument’s operational constraints. Here we describe a technique that retrospectively searches archival databases for flares jointly observed by RHESSI, SDO/EVE (MEGS-A and MEGS-B), Hinode/(EIS, SOT and XRT), and IRIS. Out of the 6,953 flares of GOES magnitude C1 or greater that we consider over the 6.5 years after the launch of SDO, 40 have been observed by six or more instruments simultaneously. The difficulty in scheduling co-ordinated observations for solar flare research is discussed with respect to instruments projected to begin operations during Solar Cycle 25, such as the Daniel K. Inouye Solar Telescope, Solar Orbiter and Solar Probe Plus.

Read this paper on arXiv…

R. Milligan and J. Ireland
Tue, 14 Mar 17
55/74

Comments: 17 pages, 6 figures, 4 tables. Submitted to Solar Physics

X-ray Temperatures, Luminosities, and Masses From XMM-Newton Follow-up of the First Shear-selected Galaxy Cluster Sample [CEA]

http://arxiv.org/abs/1703.04023


We continue the study of the first sample of shear-selected clusters (Wittman et al. 2006) from the initial 8.6 square degrees of the Deep Lens Survey (DLS, Wittman et al. 2002); a sample with well-defined selection criteria corresponding to the highest ranked shear peaks in the survey area. We aim to characterize the weak lensing selection by examining the sample’s X-ray properties. There are multiple X-ray clusters associated with nearly all the shear peaks: 14 X-ray clusters corresponding to seven DLS shear peaks. An additional three X-ray clusters cannot be definitively associated with shear peaks, mainly due to large positional offsets between the X-ray centroid and the shear peak. Here we report on the X-ray properties of the 17 X-ray clusters. The X-ray clusters display a wide range of luminosities and temperatures; the Lx-Tx relation we determine for the shear-associated X-ray clusters is consistent with X-ray cluster samples selected without regard to dynamical state, while it is inconsistent with self-similarity. For a subset of the sample, we measure X-ray masses using temperature as a proxy, and compare to weak lensing masses determined by the DLS team (Abate et al. 2009; Wittman et al. 2014). The resulting mass comparison is consistent with equality. The X-ray and weak lensing masses show considerable intrinsic scatter (~48%), which is consistent with X-ray selected samples when their X-ray and weak lensing masses are independently determined.

Read this paper on arXiv…

A. Deshpande, J. Hughes and D. Wittman
Tue, 14 Mar 17
56/74

Comments: 14 pages, 4 figures

Kiloparsec-Scale Simulations of Star Formation in Disk Galaxies. IV. Regulation of Galactic Star Formation Rates by Stellar Feedback [GA]

http://arxiv.org/abs/1703.04509


Star formation from the interstellar medium of galactic disks is a basic process controlling the evolution of galaxies. Understanding the star formation rate in a local patch of a disk with a given gas mass is thus an important challenge for theoretical models. Here we simulate a kiloparsec region of a disk, following the evolution of self-gravitating molecular clouds down to subparsec scales, as they form stars that then inject feedback energy by dissociating and ionizing UV photons and supernova explosions. We assess the relative importance of each feedback mechanism. We find that $\rm H_2$-dissociating feedback results in the largest absolute reduction in star formation compared to the run with no feedback. Subsequently adding photoionization feedback produces a more modest reduction. Our fiducial models that combine all three feedback mechanisms yield, without fine-tuning, star formation rates that are in excellent agreement with observations, with $\rm H_2$-dissociating photons playing a crucial role. Models that only include supernova feedback—a common method in galaxy evolution simulations—settle to similar star formation rates, but with very different temperature and chemical states of the gas, and with very different spatial distributions of young stars.

Read this paper on arXiv…

M. Butler, J. Tan, R. Teyssier, et. al.
Tue, 14 Mar 17
57/74

Comments: 26 pages, 18 figures, submitted to ApJ