http://arxiv.org/abs/1401.4924

Starburst galaxies are undergoing intense periods of star formation. Understanding the heating and cooling mechanisms in these galaxies can give us insight to the driving mechanisms that fuel the starburst. Molecular emission lines play a crucial role in the cooling of the excited gas. With SPIRE on the Herschel Space Observatory we have observed the rich molecular spectrum towards the central region of NGC 253. CO transitions from J=4-3 to 13-12 are observed and together with low-J line fluxes from ground based observations, these lines trace the excitation of CO. By studying the CO excitation ladder and comparing the intensities to models, we investigate whether the gas is excited by UV radiation, X-rays, cosmic rays, or turbulent heating. Comparing the $^{12}$CO and $^{13}$CO observations to large velocity gradient models and PDR models we find three main ISM phases. We estimate the density, temperature,and masses of these ISM phases. By adding $^{13}$CO, HCN, and HNC line intensities, we are able to constrain these degeneracies and determine the heating sources. The first ISM phase responsible for the low-J CO lines is excited by PDRs, but the second and third phases, responsible for the mid to high-J CO transitions, require an additional heating source. We find three possible combinations of models that can reproduce our observed molecular emission. Although we cannot determine which of these are preferable, we can conclude that mechanical heating is necessary to reproduce the observed molecular emission and cosmic ray heating is a negligible heating source. We then estimate the mass of each ISM phase; $6\times 10^7$ M$_\odot$ for phase 1 (low-J CO lines), $3\times 10^7$ M$_\odot$ for phase 2 (mid-J CO lines), and $9\times 10^6$ M$_\odot$ for phase 3 (high-J CO lines) for a total system mass of $1\times10^{8}$ M$_\odot$.

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Tue, 21 Jan 14
22/91

http://arxiv.org/abs/1401.4641

We present the results of a detailed analysis of galaxy properties along the red sequence in XMMU J1229+0151, an X-ray selected cluster at $z=0.98$ drawn from the HAWK-I Cluster Survey (HCS). Taking advantage of the broad photometric coverage and the availability of 77 spectra in the cluster field, we fit synthetic spectral energy distributions, and estimate stellar masses and photometric redshifts, which we use to determine the cluster membership. We investigate morphological and structural properties of red sequence galaxies and find that elliptical galaxies populate the bright end, while S0 galaxies represent the predominant population at intermediate luminosities, with their fraction decreasing at fainter magnitudes. A comparison with the low-redshift sample of the WINGS cluster survey reveals that at $z\sim1$ the bright end of the red sequence of XMMU J1229+0151 is richer in S0 galaxies. The faint end of the red sequence in XMMUJ1229+0151 appears rich in disc-dominated galaxies, which are rarer in the low redshift comparison sample at the same luminosities. Despite these differences between the morphological composition of the red sequence in XMMUJ1229+0151 and in low redshift samples, we find that to within the uncertainties, no such difference exists in the ratio of luminous to faint galaxies along the red sequence.

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Tue, 21 Jan 14
80/91

http://arxiv.org/abs/1401.4645

In the hierarchical structure formation scenario, galaxies enlarge through multiple merging events with less massive galaxies. In addition, the Magorrian relation indicates that almost all galaxies are occupied by a central supermassive black hole (SMBH) of mass $10^{-3}$ of its spheroidal component. Consequently, SMBHs are expected to wander in the halos of their host galaxies following a galaxy collision, although evidence of this activity is currently lacking. We investigate a current plausible location of an SMBH wandering in the halo of the Andromeda galaxy (M31). According to theoretical studies of $N$-body simulations, some of the many substructures in the M31 halo are remnants of a minor merger occurring about 1 Gyr ago. First, to evaluate the possible parameter space of the infalling orbit of the progenitor, we perform numerous parameter studies using a Graphics Processing Unit (GPU) cluster. To reduce uncertainties in the predicted position of the expected SMBH, we then calculate the time evolution of the SMBH in the progenitor dwarf galaxy from $N$-body simulations using the plausible parameter sets. Our results show that the SMBH lies within the halo ($\sim$20–50 kpc from the M31 center), closer to the Milky Way than the M31 disk. Furthermore, the predicted current positions of the SMBH were restricted to an observational field of $0\degr.6 \times 0\degr.7$ in the northeast region of the M31 halo. We also discuss the origin of the infalling orbit of the satellite galaxy and its relationships with the recently discovered vast thin disk plane of satellite galaxies around M31.

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Tue, 21 Jan 14
91/91

http://arxiv.org/abs/1401.4191

We map the kinematics of stars in simulated galaxy disks with spiral arms using the vertex deviation of the velocity ellipsoid. We use test particle simulations including, for the first time, fully self-consistent and high resolution N-body models. We compare our maps with the analytical predictions of the Tight-Winding Approximation (TWA) model. We see that, independently of the model, when the spiral arms are non-corotant the vertex deviation parameter values are related with the position of density peaks of overdense and underdense regions. We also find that if the spiral arms do not corotate with the disk, the sign of the vertex deviation changes from negative to positive when crossing the spiral arms in the direction of rotation, in the places where the spiral arms are in between corotation and the Outer Lindblad Resonance (OLR). By contrast, when they are inside the corotation radius and outside the Outer Lindblad Resonance, l$_v$ changes from negative to positive. We propose that measurements of the vertex deviations pattern can be used to trace the position of the main resonances of the spiral arms. For unbarred N-body simulations with corotant spiral arms our analysis suggests that no clear correlation exists between l$_v$ and density structures.

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Mon, 20 Jan 14
26/44

http://arxiv.org/abs/1401.4175

We review the formation and early evolution of the most massive and dense young stellar clusters, focusing on the role they can play in our understanding of star and planet formation as a whole. Young massive cluster (YMC) progenitor clouds in the Galactic Center can accumulate to a high enough density without forming stars that the initial protostellar densities are close to the final stellar density. For this to hold in the disk, the time scale to accumulate the gas to such high densities must be much shorter than the star formation timescale. Otherwise the gas begins forming stars while it is being accumulated to high density. The distinction between the formation regimes in the two environments is consistent with the predictions of environmentally-dependent density thresholds for star formation. This implies that stars in YMCs of similar total mass and radius can have formed at widely different initial protostellar densities. The fact that no systematic variations in fundamental properties are observed between YMCs in the disk and Galactic Center suggests stellar mass assembly is not strongly affected by the initial protostellar density. We review recent theoretical advances and summarize the debate on three key open questions: the initial (proto)stellar distribution, infant (im)mortality and age spreads within YMCs. We conclude: the initial protostellar distribution is likely hierarchical; YMCs likely experienced a formation history that was dominated by gas exhaustion rather than gas expulsion; YMCs are dynamically stable from a young age; and YMCs have age spreads much smaller than their mean age. Finally, we show that it is plausible that metal-rich globular clusters may have formed in a similar way to YMCs in nearby galaxies. In summary, the study of YMC formation bridges star/planet formation in the solar neighborhood to the oldest structures in the local Universe. [abridged]

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Mon, 20 Jan 14
29/44

http://arxiv.org/abs/1401.3747

We report significant inhomogeneities in the projected two-dimensional (2D) spatial distributions of Low-Mass X-ray Binaries (LMXBs) and Globular Clusters (GCs) of the intermediate mass elliptical galaxy NGC4278. In the inner region of NGC4278, a significant arc-like excess of LMXBs extending south of the center at ~50″ in the western side of the galaxy can be associated to a similar over-density of the spatial distribution of red GCs from~Brassington et al. (2009). Using a recent catalog of GCs produced by Usher et al.(2013) and covering the whole field of the NGC4278 galaxy, we have discovered two other significant density structures outside the D25 isophote to the W and E of the center of NGC4278, associated to an over-density and an under-density respectively. We discuss the nature of these structures in the context of the similar spatial inhomogeneities discovered in the LMXBs and GCs populations of NGC4649 and NGC4261, respectively. These features suggest streamers from disrupted and accreted dwarf companions.

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Fri, 17 Jan 14
20/53

http://arxiv.org/abs/1401.3759

The kinematic complexity and the favorable position of M51 on the sky make this galaxy an ideal target to test different theories of spiral arm dynamics. Taking advantage of the new high resolution PdBI Arcsecond Whirlpool Survey (PAWS) data, we undertake a detailed kinematic study of M51 to characterize and quantify the origin and nature of the non-circular motions. Using a tilted-ring analysis supported by several other archival datasets we update the estimation of M51’s position angle (PA=(173 +/- 3) deg) and inclination (i=(22 +/- 5) deg). Harmonic decomposition of the high resolution (40 pc) CO velocity field shows the first kinematic evidence of an m=3 wave in the inner disk of M51 with a corotation at R(CR,m=3)=1.1 +/- 0.1 kpc and a pattern speed of Omega_p(m=3) = 140 km/(s kpc). This mode seems to be excited by the nuclear bar, while the beat frequencies generated by the coupling between the m=3 mode and the main spiral structure confirm its density-wave nature. We observe also a signature of an m=1 mode that is likely responsible for the lopsidedness of M51 at small and large radii. We provide a simple method to estimate the radial variation of the amplitude of the spiral perturbation (Vsp) attributed to the different modes. The main spiral arm structure has <Vsp>=50-70 km/s, while the streaming velocity associated with the m=1 and m=3 modes is, in general, 2 times lower. Our joint analysis of HI and CO velocity fields at low and high spatial resolution reveals that the atomic and molecular gas phases respond differently to the spiral perturbation due to their different vertical distribution and emission morphology.

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Fri, 17 Jan 14
36/53

http://arxiv.org/abs/1401.3775

This study uses r-band images from the Eighth Data Release of the Sloan Digital Sky Survey (SDSS DR8) to study bars in lenticular (S0) galaxies in one of the nearest rich cluster environments, the Coma cluster. We develop techniques for bar detection, and assess their success when applied to SDSS image data. To detect and characterise bars we perform 2D bulge+disk+bar light decompositions of galaxy images with GALFIT. Using a sample of artificial galaxy images we determine the faintest magnitude at which bars can be successfully measured at the depth and resolution of SDSS. We perform detailed decompositions of 83 S0 galaxies in Coma, 64 from a central sample, and 19 from a cluster outskirts sample. For the central sample, the S0 bar fraction is 72^{+5}_{-6}%. This value is significantly higher than that obtained using an ellipse fitting method for bar detection, 48^{+6}_{-6}%. At a fixed luminosity, barred S0s are redder in (g-r) colour than unbarred S0s by 0.02 mag. The frequency and strength of bars increase towards fainter luminosities. Neither central metallicity nor stellar age distributions differ significantly between barred and unbarred S0s. There is an increase in the bar fraction towards the cluster core, but this is at a low significance level. Bars have at most a weak correlation with cluster-centric radius.

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Fri, 17 Jan 14
45/53

http://arxiv.org/abs/1401.3340

We present analysis of two O VI absorbers at redshift z_{abs} = 0.227, detected in the spectra of two closely spaced QSO sightlines (Q 0107-025 A and B), observed with the Cosmic Origins Spectrograph (COS) on board the Hubble Space Telescope (HST). At the same redshift, presence of a single bright (~ 1.2 L*) galaxy at an impact parameter of ~ 200 kpc (proper) from both the sightlines was reported by Crighton et al. (2010). Using detailed photoionization models we show that the high ionization phases of both the O VI absorbers have similar ionization conditions (e.g. log U ~ -1.1 to -0.9), chemical enrichment (e.g. log Z ~ -1.4 to -1.0), total hydrogen column density (e.g. log N_{H} (cm^{-2}) ~ 19.6-19.7) and line of sight thickness (e.g. l_{los} ~ 600-800 kpc). Therefore we speculate that the O VI absorbers are tracing different parts of same large scale structure, presumably the circumgalactic medium (CGM) of the identified galaxy. Using sizes along and transverse to the line of sight, we estimate the size of the CGM to be R ~ 330 kpc. The baryonic mass associated with this large CGM as traced by O VI absorption is ~ 1.2×10^{11} M_{sun}. A low ionization phase is detected in one of the O VI systems with near solar metallicity (log Z = 0.20\pm0.20) and parsec scale size (l_{los} ~ 6 pc), possibly tracing the neutral phase of a high velocity cloud (HVC) embedded within the CGM.

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Thu, 16 Jan 14
31/53

http://arxiv.org/abs/1401.3334

We measure the redshift evolution of the bar fraction in a sample of 2380 visually selected disc galaxies found in Cosmic Evolution Survey (COSMOS) Hubble Space Telescope (HST) images. The visual classifications used to identify both the disc sample and to indicate the presence of stellar bars were provided by citizen scientists via the Galaxy Zoo: Hubble (GZH) project. We find that the overall bar fraction decreases by a factor of two, from 22+/-5% at z=0.4 (tlb = 4.2 Gyr) to 11+/-2% at z=1.0 (tlb = 7.8 Gyr), consistent with previous analysis. We show that this decrease, of the strong bar fraction in a volume limited sample of massive disc galaxies [stellar mass limit of log(Mstar/Msun) > 10.0], cannot be due to redshift dependent biases hiding either bars or disc galaxies at higher redshifts. Splitting our sample into three bins of mass we find that the decrease in bar fraction is most prominent in the highest mass bin, while the lower mass discs in our sample show a more modest evolution. We also include a sample of 98 red disc galaxies. These galaxies have a high bar fraction (45+/-5%), and are missing from other COSMOS samples which used SED fitting or colours to identify high redshift discs. Our results are consistent with a picture in which the evolution of massive disc galaxies begins to be affected by slow (secular) internal process at z~1. We discuss possible connections of the decrease in bar fraction to the redshift, including the growth of stable disc galaxies, mass evolution of the gas content in disc galaxies, as well as the mass dependent effects of tidal interactions.

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Thu, 16 Jan 14
39/53

http://arxiv.org/abs/1401.3002

We compile a sample of dispersion-supported and rotation-supported galaxies for which the dynamical mass enclosed at 500 pc can be measured. We find that this dynamical quantity increases only slowly with stellar mass (M$_{total}$(<500pc) $\propto$ M$_{stars}$$^{0.16}$) over ~9 decades in baryonic mass and ~3 in length scale, with a sudden upturn at the highest masses (M$_{stars}$ > 10$^{10}$M$_{sun}$). This upturn occurs for the earliest type (S0 and Sa) disk galaxies, and is consistent with the “extra” mass within 500 pc being predominantly stellar. This sudden change may be indicative of different bulge formation mechanisms between early and late type disks. We also compare the data to the results of recent galaxy formation simulations. These broadly track the observed trend, with some tendency to put too much mass in the inner 500 pc, depending on the details of each simulation.

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Wed, 15 Jan 14
12/67

http://arxiv.org/abs/1401.3248

To understand the relation between the small “obscuring torus” and dusty structures at larger scales (5-10 pc) in NGC 1068, we use ESO’s Mid-Infrared Interferometer (MIDI) with the 1.8 m Auxiliary Telescopes to achieve the necessary spatial resolution (~ 20-100 millarcsec). We use the chromatic phases in the data to improve the spatial fidelity of the analysis. We present interferometric data for NGC 1068 obtained in 2007 and 2012. We find no evidence of source variability. Many (u,v) points show non-zero chromatic phases indicating significant asymmetries. Gaussian model fitting of the correlated fluxes and chromatic phases provides a 3-component best fit with estimates of sizes, temperatures and positions of the components. A large, warm, off-center component is required at a distance approximately 90 mas to the north-west at a PA ~ -18 deg. The dust at 5-10 pc in the polar region contributes 4 times more to the mid-infrared flux at 12 um than the dust located at the center. This dust may represent the inner wall of a dusty cone. If similar regions are heated by the direct radiation from the nucleus, then they will contribute substantially to the classification of many Seyfert galaxies as Type 2. Such a region is also consistent in other Seyfert galaxies (the Circinus galaxy, NGC 3783 and NGC 424).

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Wed, 15 Jan 14
13/67

http://arxiv.org/abs/1401.3228

We present the search for the [CII] emission line in three $z>6.5$ Lyman-alpha emitters (LAEs) and one J-Dropout galaxy using the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and the Plateau de Bure Interferometer (PdBI). We observed three bright $z\sim6.5-7$ LAEs discovered in the SUBARU deep field (SDF) and the Multiple Imaged lensed $z\sim 11$ galaxy candidate found behind the galaxy cluster MACSJ0647.7+7015. For the LAEs IOK-1 ($z=6.965$), SDF J132415.7+273058 ($z=6.541$) and SDF J132408.3+271543 ($z=6.554$) we find upper limits for the [CII] line luminosity of $<2.05$, $<4.52$ and $<10.56\times10^{8}{\rm L}_{\odot}$ respectively. We find upper limits to the FIR luminosity of the galaxies using a spectral energy distribution template of the local galaxy NGC 6946 and taking into account the effects of the Cosmic Microwave Background on the mm observations. For IOK-1, SDF J132415.7+273058 and SDF J132408.3+271543 we find upper limits for the FIR luminosity of $<2.33$, $3.79$ and $7.72\times10^{11}{\rm L}_{\odot}$ respectively. For the lensed galaxy MACS0647-JD, one of the highest redshift galaxy candidate to date with $z_{\rm ph}=10.7^{+0.6}_{-0.4}$ we put an upper limit in the [CII] emission of $<1.36\times10^{8}\times(\mu/15)^{-1}{\rm L}_{\odot}$ and an upper limit in the FIR luminosity of $<6.1\times10^{10}\times(\mu/15)^{-1}{\rm L}_{\odot}$ (where $\mu$ is the magnification factor). We explore the different conditions relevant for the search for [CII] emission in high redshift galaxies as well as the difficulties for future observations with ALMA and CCAT.

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Wed, 15 Jan 14
17/67

http://arxiv.org/abs/1401.2994

We report significant anisotropies in the projected two-dimensional (2D) spatial distributions of Globular Clusters (GCs) of the giant Virgo elliptical galaxy NGC4649 (M60). Similar features are found in the 2D distribution of low-mass X-ray binaries (LMXBs), both associated with GCs and in the stellar field. Deviations from azimuthal symmetry suggest an arc-like excess of GCs extending north at 4-15 kpc galactocentric radii in the eastern side of major axis of NGC4649. This feature is more prominent for red GCs, but still persists in the 2D distribution of blue GCs. High and low luminosity GCs also show some segregation along this arc, with high-luminosity GCs preferentially located in the southern end and low-luminosity GCs in the northern section of the arc. GC-LMXBs follow the anisotropy of red-GCs, where most of them reside; however, a significant overdensity of (high-luminosity) field LMXBs is present to the south of the GC arc. These results suggest that NGC4649 has experienced mergers and/or multiple accretions of less massive satellite galaxies during its evolution, of which the GCs in the arc may be the fossil remnant. We speculate that the observed anisotropy in the field LMXB spatial distribution indicates that these X-ray binaries may be the remnants of a star formation event connected with the merger, or maybe be ejected from the parent red GCs, if the bulk motion of these clusters is significantly affected by dynamical friction. We also detect a luminosity enhancement in the X-ray source population of the companion spiral galaxy NGC4647. We suggest that these may be younger high mass X-ray binaries formed as a result of the tidal interaction of this galaxy with NGC4649.

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Wed, 15 Jan 14
44/67

http://arxiv.org/abs/1401.3131

We use deep Chandra X-ray Observatory observations to examine the coronae of the two brightest cluster galaxies in the Coma cluster of galaxies, NGC 4874 and NGC 4889. We find that NGC 4889 hosts a central depression in X-ray surface brightness consistent with a cavity or pair of cavities of radius 0.6 kpc. If the central cavity is associated with an AGN outburst and contains relativistic material, its enthalpy should be around 5×10^55 erg. The implied heating power of this cavity would be around an order of magnitude larger than the energy lost by X-ray emission. It would be the smallest and youngest known cavity in a brightest cluster galaxy and the lack of over pressuring implies heating is still gentle. In contrast, NGC 4874 does not show any evidence for cavities, although it hosts a well-known wide-angle-tail radio source which is visible outside the region occupied by the X-ray corona. These two galaxies show that AGN feedback can behave in varied ways in the same cluster environment.

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Wed, 15 Jan 14
45/67

http://arxiv.org/abs/1401.2985

I present a new framework for modeling the dynamics of tidal streams. The framework consists of simple models for the initial action-angle distribution of tidal debris, which can be straightforwardly evolved forward in time. Taking advantage of the essentially one-dimensional nature of tidal streams, the transformation to position-velocity coordinates can be linearized and interpolated near a small number of points along the progenitor orbit, thus allowing for efficient computations of a stream’s properties in observable quantities. I illustrate how to calculate the stream’s average location (its ‘track’) in different coordinate systems, how to quickly estimate the dispersion around its track, and how to draw mock stream data. As a generative model, this framework allows one to compute the full probability distribution function and marginalize over or condition it on certain phase-space dimensions as well as convolve it with observational uncertainties. This will be instrumental in proper data analysis of stream data. In addition to providing a computationally-efficient practical tool for modeling the dynamics of tidal streams, the action-angle nature of the framework helps elucidate in exactly what manner streams do not follow single orbits, how the observed width of the stream relates to the velocity dispersion or mass of the progenitor, and how the progenitors of ‘orphan’ streams could be located.
The practical usefulness of the proposed framework crucially depends on the ability to calculate action-angle variables for any orbit in any gravitational potential. A novel method for calculating actions, frequencies, and angles in any static potential using a single orbit integration is described in an Appendix.

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Wed, 15 Jan 14
49/67

http://arxiv.org/abs/1401.2473

Stars do not generally form in isolation. Instead, they form in clusters, and in these clustered environments newborn stars can have profound effects on one another and on their parent gas clouds. Feedback from clustered stars is almost certainly responsible for a number of otherwise puzzling facts about star formation: that it is an inefficient process that proceeds slowly when averaged over galactic scales; that most stars disperse from their birth sites and dissolve into the galactic field over timescales $\ll 1$ Gyr; and that newborn stars follow an initial mass function (IMF) with a distinct peak in the range $0.1 – 1$ $M_\odot$, rather than an IMF dominated by brown dwarfs. In this review we summarize current observational constraints and theoretical models for the complex interplay between clustered star formation and feedback.

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Tue, 14 Jan 14
11/72

http://arxiv.org/abs/1401.2492

We present a spectroscopic study of the four extended star clusters (ESCs) in NGC 6822 based on the data obtained with Gemini Multi-Object Spectrograph (GMOS) on the Gemini-South 8.1m telescope. Their radial velocities derived from the spectra range from $-61.2 \pm 20.4$ km s$^{-1}$ (for C1) to $-115.34 \pm 57.9$ km s$^{-1}$ (for C4) and, unlike the intermediate age carbon stars, they do not display any sign of systematic rotation around NGC 6822. The ages and metallicities derived using the Lick indices show that the ESCs are old ($\geq 8$ Gyr) and metal poor ([Fe/H]$\lesssim -1.5$). NGC 6822 is found to have both metal poor ([Fe/H]$\approx -2.0$) and metal rich ([Fe/H]$\approx -0.9$) star clusters within 15 arcmin (2 kpc) from the center, while only metal poor clusters are observed in the outer halo with $r \geq 20$ arcmin (2.6 kpc). The kinematics, old ages, and low metallicities of ESCs suggest that ESCs may have accreted into the halo of NGC 6822. Based on the velocity distribution of ESCs, we have determined the total mass and the mass-to-light ratio of NGC 6822: $M_{N6822} = 7.5^{+4.5}_{-0.1} \times 10^{9} M_{\odot}$ and $(M/L)_{N6822} = 75^{+45}_{-1} (M/L)_{\odot}$. It shows that NGC 6822 is one of the most dark matter dominated dwarf galaxies in the Local Group.

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Tue, 14 Jan 14
44/72

http://arxiv.org/abs/1401.2562

With the aim to determine the spatial distribution of dark matter, we investigate the polar ring galaxy NGC 4262. We used the stellar kinematics data for the central galaxy obtained from optical spectroscopy together with information about the kinematics of the neutral hydrogen for polar component. It was shown that NGC 4262 is the classic polar ring galaxy case with the relative angle of $88^{\circ}$ between components. From simulations of the central galaxy and ring kinematics we found that the shape of the dark matter distribution varies strongly with the radius. Namely, the dark matter halo is flattened towards the galactic disk plane $c/a=0.4$, however it is prolate to the orthogonal (polar) plane far beyond the central galaxy $c/a=1.7$. Also, the simulations of the ring evolution let us to confirm the stability of the ring and the formation of quasi-spiral structures within it.

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Tue, 14 Jan 14
61/72

http://arxiv.org/abs/1401.2455

We have undertaken an ambitious program to visually classify all galaxies in the five CANDELS fields down to H<24.5 involving the dedicated efforts of 65 individual classifiers. Once completed, we expect to have detailed morphological classifications for over 50,000 galaxies up to z<4 over all the fields. Here, we present our detailed visual classification scheme, which was designed to cover a wide range of CANDELS science goals. This scheme includes the basic Hubble sequence types, but also includes a detailed look at mergers and interactions, the clumpiness of galaxies, $k$-corrections, and a variety of other structural properties. In this paper, we focus on the first field to be completed — GOODS-S. The wide area coverage spanning the full field includes 7634 galaxies that have been classified by at least three different people. In the deep area of the field, 2534 galaxies have been classified by at least five different people at three different depths. With this paper, we release to the public all of the visual classifications in GOODS-S along with the GUI that we developed to classify galaxies. We find that the level of agreement among classifiers is good and depends on both the galaxy magnitude and the galaxy type, with disks showing the highest level of agreement and irregulars the lowest. A comparison of our classifications with the Sersic index and rest-frame colors shows a clear separation between disk and spheroid populations. Finally, we explore morphological k-corrections between the V-band and H-band observations and find that a small fraction (84 galaxies in total) are classified as being very different between these two bands. These galaxies typically have very clumpy and extended morphology or are very faint in the V-band.

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Mon, 13 Jan 14
2/39

http://arxiv.org/abs/1401.2179

We present the results of recent studies on the co-evolution of galaxies and the supermassive black holes (SMBHs) using Herschel far-infrared and Chandra X-ray observations in the Bo\”otes survey region. For a sample of star-forming (SF) galaxies, we find a strong correlation between galactic star formation rate and the average SMBH accretion rate in SF galaxies. Recent studies have shown that star formation and AGN accretion are only weakly correlated for individual AGN, but this may be due to the short variability timescale of AGN relative to star formation. Averaging over the full AGN population yields a strong linear correlation between accretion and star formation, consistent with a simple picture in which the growth of SMBHs and their host galaxies are closely linked over galaxy evolution time scales.

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Mon, 13 Jan 14
31/39