Unsupervised Method for Correlated Noise Removal for Multi-wavelength Exoplanet Transit Observations [IMA]


Exoplanetary atmospheric observations require an exquisite precision in the measurement of the relative flux among wavelengths. In this paper, we aim to provide a new adaptive method to treat light curves before fitting transit parameters in order to minimize systematic effects that affect, for instance, ground-based observations of exo-atmospheres. We propose a neural-network-based method that uses a reference built from the data itself with parameters that are chosen in an unsupervised fashion. To improve the performance of proposed method, K-means clustering and Silhouette criteria are used for identifying similar wavelengths in each cluster. We also constrain under which circumstances our method improves the measurement of planetary-to-stellar radius ratio without producing significant systematic offset. We tested our method in high quality data from WASP-19b and low quality data from GJ-1214. We succeed in providing smaller error bars for the former when using JKTEBOP, but GJ-1214 light curve was beyond the capabilities of this method to improve as it was expected from our validation tests.

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A. Firoozabadi, A. Diaz, P. Rojo, et. al.
Wed, 28 Jun 17

Comments: 14 pages, 18 figures

LBT observations of compact star-forming galaxies with extremely high [OIII]/[OII] flux ratios: HeI emission-line ratios as diagnostics of Lyman continuum leakage [GA]


We present Large Binocular Telescope spectrophotometric observations of five low-redshift (z<0.070) compact star-forming galaxies (CSFGs) with extremely high emission-line ratios O32 = [OIII]5007/[OII]3727, ranging from 23 to 43. Galaxies with such high O32 are thought to be promising candidates for leaking large amounts of Lyman continuum (LyC) radiation and, at high redshifts, for contributing to the reionization of the Universe. The equivalent widths EW(Hbeta) of the Hbeta emission line in the studied galaxies are very high, ~350-520A, indicating very young ages for the star formation bursts, <3 Myr. All galaxies are characterized by low oxygen abundances 12+logO/H = 7.46 – 7.79 and low masses Mstar~10^6-10^7 Msun, much lower than the Mstar for known low-redshift LyC leaking galaxies, but probably more typical of the hypothetical population of low-luminosity dwarf LyC leakers at high redshifts. A broad Halpha emission line is detected in the spectra of all CSFGs, possibly related to expansion motions of supernova remnants. Such rapid ionized gas motions would facilitate the escape of the resonant Ly$\alpha$ emission from the galaxy. We show that high O32 may not be a sufficient condition for LyC leakage and propose new diagnostics based on the HeI 3889/6678 and 7065/6678 emission-line flux ratios. Using these diagnostics we find that three CSFGs in our sample are likely to have density-bounded HII regions and are thus leaking large amounts of LyC radiation. The amount of leaking LyC radiation is probably much lower in the other two CSFGs.

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Y. Izotov, T. Thuan and N. Guseva
Wed, 28 Jun 17

Comments: 16 pages, 8 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society

DEPFET detectors for direct detection of MeV Dark Matter particles [CL]


The existence of dark matter is undisputed, while the nature of it is still unknown. Explaining dark matter with the existence of a new unobserved particle is among the most promising possible solutions. Recently dark matter candidates in the MeV mass region received more and more interest. In comparison to the mass region between a few GeV to several TeV, this region is experimentally largely unexplored. We discuss the application of a RNDR DEPFET semiconductor detector for direct searches for dark matter in the MeV mass region. We present the working principle of the RNDR DEPFET devices and review the performance obtained by previously performed prototype measurements. The future potential of the technology as dark matter detector is discussed and the sensitivity for MeV dark matter detection with RNDR DEPFET sensors is presented. Under the assumption of three background events in the region of interest and an exposure of one kg$\cdot$y a sensitivity of $\bar{\sigma}_{\bar{e}} = 10^{-41}$ cm$^{2}$ for dark matter particles with a mass of 10 MeV can be reached.

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A. Baehr, H. Kluck, J. Ninkovic, et. al.
Wed, 28 Jun 17

Comments: N/A

On the SFR-M$_*$ main sequence archetypal star-formation history and analytical models [GA]


We derive the SFH of MS galaxies showing how the SFH peak of a galaxy depends on its seed mass at e.g. z=5. Following the MS, galaxies undergo a drastic slow down of their stellar mass growth after reaching the peak of their SFH. According to abundance matching, these masses correspond to hot and massive DM halos which state could results in less efficient gas inflows on the galaxies and thus could be at the origin of the limited stellar mass growth. As a result, galaxies on the MS can enter the passive region of the UVJ diagram while still forming stars. The ability of the classical analytical SFHs to retrieve the SFR of galaxies from SED fitting is studied. Due to mathematical limitations, the exp-declining and delayed SFH struggle to model high SFR which starts to be problematic at z>2. The exp-rising and log-normal SFHs exhibit the opposite behavior with the ability to reach very high SFR, and thus model starburst galaxies, but not low values such as those expected at low redshift for massive galaxies. We show that these four analytical forms recover the SFR of MS galaxies with an error dependent on the model and the redshift. They are, however, sensitive enough to probe small variations of SFR within the MS but all the four fail to recover the SFR of rapidly quenched galaxies. However, these SFHs lead to an artificial gradient of age, parallel to the MS which is not exhibited by a simulated sample. This gradient is also produced on real data, using a sample of GOODS-South galaxies at 1.5<z<1.2. We propose a SFH composed of a delayed form to model the bulk of stellar population plus a flexibility in the recent SFH. This SFH provides very good estimates of the SFR of MS, starbursts, and rapidly quenched galaxies at all z. Furthermore, used on the GOODS-South sample, the age gradient disappears, showing its dependency on the SFH assumption made to perform the SED fitting.

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L. Ciesla, D. Elbaz and J. Fensch
Wed, 28 Jun 17

Comments: Submitted to A&A, includes first round of referee’s comments

First Detection of HC$_{5}$$^{15}$N in the Interstellar Medium [GA]


We report the first detection of HC${5}$$^{15}$N with the $J=9-8$ rotational line from the cyanopolyyne peak in Taurus Molecular Cloud-1 (TMC-1 CP) using the 45-m radio telescope of the Nobeyama Radio Observatory. The column density of HC${5}$$^{15}$N is derived to be (1.9 +- 0.5)*$10^{11}$ cm$^{-2}$ (1 sigma). We apply the double isotope method to derive the $^{14}$N/$^{15}$N ratios of HC$_{5}$N and HC$_{3}$N in TMC-1 CP. The $^{14}$N/$^{15}$N ratios are calculated to be 344 +- 53 and 257 +- 54 for HC$_{5}$N and HC$_{3}$N, respectively. The $^{14}$N/$^{15}$N ratio of HC$_{5}$N is lower than the elemental ratio in the local interstellar medium (~440) and slightly higher than that of HC$_{3}$N in TMC-1 CP. Since HC$_{3}$N is formed via the neutral-neutral reaction between C$_{2}$H$_{2}$ and CN, the slightly higher $^{14}$N/$^{15}$N ratio of HC$_{5}$N may support our previous suggestions that the main formation mechanism of HC$_{5}$N is the ion-molecule reactions between hydrocarbon ions (C$_{5}$H$_{n}^{+}$) and nitrogen atoms.

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K. Taniguchi and M. Saito
Wed, 28 Jun 17

Comments: Accepted by PASJ (Publications of the Astronomical Society of Japan) letter, 1 Figure, 2 Tables

Oscillating Affleck-Dine condensate and its cosmological implications [CL]


We study the dynamics of the Affleck-Dine field after inflation in more detail. After inflation, the Affleck-Dine field inevitably oscillates around the potential minimum. This oscillation is hard to decay and can cause accidental suppression of the consequential baryon asymmetry. This suppression is most effective for the model with non-renormalizable superpotential $W_{AD}\sim \Phi^4$ ($\Phi$: Affleck-Dine field). It is found that the Affleck-Dine leptogenesis in high-scale inflation, which suffers from serious gravitino overproduction, becomes workable owing to this effect.

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F. Hasegawa and M. Kawasaki
Wed, 28 Jun 17

Comments: 6 pages, 6 figures

Simulating the effect of high column density absorbers on the one-dimensional Lyman-alpha forest flux power spectrum [CEA]


We measure the effect of high column density absorbing systems of neutral hydrogen (HI) on the one-dimensional (1D) Lyman-alpha forest flux power spectrum using cosmological hydrodynamical simulations from the Illustris project. High column density absorbers (which we define to be those with HI column densities $N(\mathrm{HI}) > 1.6 \times 10^{17}\,\mathrm{atoms}\,\mathrm{cm}^{-2}$) cause broadened absorption lines with characteristic damping wings. These damping wings bias the 1D Lyman-alpha forest flux power spectrum by causing absorption in quasar spectra away from the location of the absorber itself. We investigate the effect of high column density absorbers on the Lyman-alpha forest using hydrodynamical simulations for the first time. We provide templates as a function of column density and redshift, allowing the flexibility to accurately model residual contamination, i.e., if an analysis selectively clips out the largest damping wings. This flexibility will improve cosmological parameter estimation, e.g., allowing more accurate measurement of the shape of the power spectrum, with implications for cosmological models containing massive neutrinos or a running of the spectral index. We provide fitting functions to reproduce these results so that they can be incorporated straightforwardly into a data analysis pipeline.

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K. Rogers, S. Bird, H. Peiris, et. al.
Wed, 28 Jun 17

Comments: 11 pages, 5 figures. To be submitted to MNRAS