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标题：UV and Ly α luminosity functions of galaxies and star formation rate density at the end of HI reionization from the VIMOS UltraDeep Survey (VUDS) ⋆
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作者：O. Le Fèvre ; P. Cassata ; O. Cucciati 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2020
卷号：634
页码：1-26
DOI：10.1051/0004-6361/201935400
语种：English
出版社：EDP Sciences
摘要：Context.The star formation rate density (SFRD) evolution presents an area of great interest in the studies of galaxy evolution and reionization. The current constraints of SFRD atz > 5 are based on the rest-frame UV luminosity functions with the data from photometric surveys. The VIMOS UltraDeep Survey (VUDS) was designed to observe galaxies at redshifts up to ∼6 and opened a window for measuring SFRD atz > 5 from a spectroscopic sample with a well-controlled selection function.Aims.We establish a robust statistical description of the star-forming galaxy population at the end of cosmic HI reionization (5.0 ≤ z ≤ 6.6) from a large sample of 49 galaxies with spectroscopically confirmed redshifts. We determine the rest-frame UV and Lyαluminosity functions and use them to calculate SFRD at the median redshift of our samplez = 5.6.Methods.We selected a sample of galaxies at 5.0 ≤ zspec ≤ 6.6 from the VUDS. We cleaned our sample from low redshift interlopers using ancillary photometric data. We identified galaxies with Lyαeither in absorption or in emission, at variance with most spectroscopic samples in the literature where Lyαemitters (LAE) dominate. We determined luminosity functions using the 1/Vmaxmethod.Results.The galaxies in this redshift range exhibit a large range in their properties. A fraction of our sample shows strong Lyαemission, while another fraction shows Lyαin absorption. UV-continuum slopes vary with luminosity, with a large dispersion. We find that star-forming galaxies at these redshifts are distributed along the main sequence in the stellar mass vs. SFR plane, described with a slopeα = 0.85 ± 0.05. We report a flat evolution of the specific SFR compared to lower redshift measurements. We find that the UV luminosity function is best reproduced by a double power law, while a fit with a Schechter function is only marginally inferior. The Lyαluminosity function is best fitted with a Schechter function. We derive a logSFRDUV(M⊙yr−1Mpc−3) = −1.45+0.06−0.08and logSFRDLyα(M⊙yr−1Mpc−3) = −1.40+0.07−0.08. The SFRD derived from the Lyαluminosity function is in excellent agreement with the UV-derived SFRD after correcting for IGM absorption.Conclusions.Our new SFRD measurements at a mean redshift ofz = 5.6 are ∼0.2 dex above the mean SFRD reported in Madau & Dickinson (2014, ARA&A, 52, 415), but in excellent agreement with results from Bouwens et al. (2015a, ApJ, 803, 34). These measurements confirm the steep decline of the SFRD atz > 2. The bright end of the Lyαluminosity function has a high number density, indicating a significant star formation activity concentrated in the brightest LAE at these redshifts. LAE with equivalent width EW > 25 Å contribute to about 75% of the total UV-derived SFRD. While our analysis favors low dust content in 5.0 < z < 6.6, uncertainties on the dust extinction correction and associated degeneracy in spectral fitting will remain an issue, when estimating the total SFRD until future surveys extending spectroscopy to the NIR rest-frame spectral domain, such as with JWST.
关键词：engalaxies: high-redshiftgalaxies: evolutiongalaxies: formationgalaxies: star formationdark ages, reionization, first starsgalaxies: luminosity function, mass function