E. Merlin

The Evolution of the Galaxy Rest-Frame Ultraviolet Luminosity Function Over the First Two Billion Years

We present a robust measurement and analysis of the rest-frame ultraviolet (UV) luminosity functions at z = 4-8. We use deep Hubble Space Telescope imaging over the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey/GOODS fields, the Hubble Ultra Deep Field, and the Hubble Frontier Field deep parallel observations near the Abell 2744 and MACS J0416.1-2403 clusters. The combination of these surveys provides an effective volume of 0.6-1.2 x 10(6) Mpc(3) over this epoch, allowing us to perform a robust search for faint (M-UV = -18) and bright (Muv \textless -21) high-redshift galaxies. We select candidate galaxies using a well-tested photometric redshift technique with careful screening of contaminants, finding a sample of 7446 candidate galaxies at 3.5 \textless z \textless 8.5, with \textgreater1000 galaxies at z approximate to 6-8. We measure both a stepwise luminosity function for candidate galaxies in our redshift samples, and a Schechter function, using a Markov Chain Monte Carlo analysis to measure robust uncertainties. At the faint end, our UV luminosity functions agree with previous studies, yet we find a higher abundance of UV-bright candidate galaxies at z \textgreater= 6. Our best-fit value of the characteristic magnitude MN is consistent with -21 at z \textgreater=, 5, which is different than that inferred based on previous trends at lower redshift, and brighter at similar to 2 sigma significance than previous measures at z = 6 and 7. At z = 8, a single power law provides an equally good fit to the UV luminosity function, while at z = 6 and 7 an exponential cutoff at the bright end is moderately preferred. We compare our luminosity functions to semi-analytical models, and find that the lack of evolution in M-UV(*) is consistent with models where the impact of dust attenuation on the bright end of the luminosity function decreases at higher redshift, although a decreasing impact of feedback may also be possible. We measure the evolution of the cosmic star-formation rate (SFR) density by integrating our observed luminosity functions to M-UV = -17, correcting for dust attenuation, and find that the SFR density declines proportionally to (1 +z)(-4.3 +/- 0 5) at z \textgreater 4, which is consistent with observations at z \textgreater= 9. Our observed luminosity functions are consistent with a reionization history that starts at z greater than or similar to 10, completes at z \textgreater 6, and reaches a midpoint (xH = 0.5) at 6.7 \textless z \textless9.4. Finally, using a constant cumulative number density selection and an empirically derived rising star-formation history, our observations predict that the abundance of bright z = 9 galaxies is likely higher than previous constraints, although consistent with recent estimates of bright z similar to 10 galaxies.

The galaxy stellar mass function at 3.5 ≤ z ≤ 7.5 in the CANDELS/UDS, GOODS-South, and HUDF fields

Context. The form and evolution of the galaxy stellar mass function (GSMF) at high redshifts provide crucial information on star formation history and mass assembly in the young Universe, close or even prior to the epoch of reionization. Aims. We used the unique combination of deep optical/near-infrared/mid-infrared imaging provided by HST, Spitzer, and the VLT in the CANDELS-UDS, GOODS-South, and HUDF fields to determine the GSMF over the redshift range 3.5 ≤ z ≤ 7.5. Methods. We used the HST WFC3/IR near-infrared imaging from CANDELS and HUDF09, reaching H ≃ 27 − 28.5 over a total area of 369 arcmin^2, in combination with associated deep HST ACS optical data, deep Spitzer IRAC imaging from the SEDS programme, and deep Y and K-band VLT Hawk-I images from the HUGS programme, to select a galaxy sample with high-quality photometric redshifts. These have been calibrated with more than 150 spectroscopic redshifts in the range 3.5 ≤ z ≤ 7.5, resulting in an overall precision of σ_z/ (1 + z) ~ 0.037. With this database we have determined the low-mass end of the high-redshift GSMF with unprecedented precision, reaching down to masses as low as M^∗ ~ 10^9 M_⊙ at z = 4 and ~6 × 10^9 M_⊙ at z = 7. Results. We find that the GSMF at 3.5 ≤ z ≤ 7.5 depends only slightly on the recipes adopted to measure the stellar masses, namely the photometric redshifts, the star formation histories, the nebular contribution, or the presence of AGN in the parent sample. The low-mass end of the GSMF is steeper than has been found at lower redshifts, but appears to be unchanged over the redshift range probed here. Meanwhile the high-mass end of the GSMF appears to evolve primarily in density, although there is also some evidence of evolution in characteristic mass. Our results are very different from previous mass function estimates based on converting UV galaxy luminosity functions into mass functions via tight mass-to-light relations. Integrating our evolving GSMF over mass, we find that the growth of stellar mass density is barely consistent with the time-integral of the star formation rate density over cosmic time at z> 4. Conclusions. These results confirm the unique synergy of the CANDELS+HUDF, HUGS, and SEDS surveys for the discovery and study of moderate/low-mass galaxies at high redshifts, and reaffirm the importance of space-based infrared selection for the unbiased measurement of the evolving GSMF in the young Universe.The galaxy stellar mass function (GSMF) at high-z provides key information on star-formation history and mass assembly in the young Universe. We aimed to use the unique combination of deep optical/NIR/MIR imaging provided by HST, Spitzer and the VLT in the CANDELS-UDS, GOODS-South, and HUDF fields to determine the GSMF over the redshift range 3.5 4. These results confirm the unique synergy of the CANDELS+HUDF, HUGS, and SEDS surveys for the discovery and study of moderate/low-mass galaxies at high redshifts.

STELLAR MASSES FROM THE CANDELS SURVEY: THE GOODS-SOUTH AND UDS FIELDS

We present the public release of the stellar mass catalogs for the GOODS-S and UDS fields obtained using some of the deepest near-IR images available, achieved as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey project. We combine the effort from 10 different teams, who computed the stellar masses using the same photometry and the same redshifts. Each team adopted their preferred fitting code, assumptions, priors, and parameter grid. The combination of results using the same underlying stellar isochrones reduces the systematics associated with the fitting code and other choices. Thanks to the availability of different estimates, we can test the effect of some specific parameters and assumptions on the stellar mass estimate. The choice of the stellar isochrone library turns out to have the largest effect on the galaxy stellar mass estimates, resulting in the largest distributions around the median value (with a semi interquartile range larger than 0.1 dex). On the other hand, for most galaxies, the stellar mass estimates are relatively insensitive to the different parameterizations of the star formation history. The inclusion of nebular emission in the model spectra does not have a significant impact for the majority of galaxies (less than a factor of 2 for ~80% of the sample). Nevertheless, the stellar mass for the subsample of young galaxies (age <100 Myr), especially in particular redshift ranges (e.g., 2.2 < z < 2.4, 3.2 < z < 3.6, and 5.5 < z < 6.5), can be seriously overestimated (by up to a factor of 10 for <20 Myr sources) if nebular contribution is ignored.

THE EVOLUTION OF THE GALAXY STELLAR MASS FUNCTION AT z = 4–8: A STEEPENING LOW-MASS-END SLOPE WITH INCREASING REDSHIFT

We present galaxy stellar mass functions (GSMFs) at

T-PHOT: A new code for PSF-matched, prior-based, multiwavelength extragalactic deconfusion photometry

z=

The ASTRODEEP Frontier Fields catalogues - II. Photometric redshifts and rest frame properties in Abell-2744 and MACS-J0416

4-8 from a rest-frame ultraviolet (UV) selected sample of

The Lyman continuum escape fraction of galaxies at z=3.3 in the VUDS-LBC/COSMOS field

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Paving the way for the JWST: witnessing globular cluster formation at z > 3

4500 galaxies, found via photometric redshifts over an area of

The ASTRODEEP Frontier Fields catalogues - I. Multiwavelength photometry of Abell-2744 and MACS-J0416

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THE GRISM LENS-AMPLIFIED SURVEY FROM SPACE (GLASS). IV. MASS RECONSTRUCTION OF THE LENSING CLUSTER ABELL 2744 FROM FRONTIER FIELD IMAGING AND GLASS SPECTROSCOPY

280 arcmin