UV and Lyα luminosity functions of galaxies and star formation rate density at the end of HI reionization from the VIMOS UltraDeep Survey (VUDS)

Medientyp: E-Artikel
Titel: UV and Lyα luminosity functions of galaxies and star formation rate density at the end of HI reionization from the VIMOS UltraDeep Survey (VUDS)
Beteiligte: Khusanova, Y.; Le Fèvre, O.; Cassata, P.; Cucciati, O.; Lemaux, B. C.; Tasca, L. A. M.; Thomas, R.; Garilli, B.; Le Brun, V.; Maccagni, D.; Pentericci, L.; Zamorani, G.; Amorín, R.; Bardelli, S.; Castellano, M.; Cassarà, L. P.; Cimatti, A.; Giavalisco, M.; Hathi, N. P.; Ilbert, O.; Koekemoer, A. M.; Marchi, F.; Pforr, J.; Ribeiro, B.; [...]
Erschienen: EDP Sciences, 2020
Erschienen in: Astronomy & Astrophysics
Sprache: Nicht zu entscheiden
DOI: 10.1051/0004-6361/201935400
ISSN: 0004-6361; 1432-0746
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Beschreibung: <jats:p><jats:italic>Context.</jats:italic> 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 at <jats:italic>z</jats:italic> > 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 at <jats:italic>z</jats:italic> > 5 from a spectroscopic sample with a well-controlled selection function.</jats:p> <jats:p><jats:italic>Aims.</jats:italic> We establish a robust statistical description of the star-forming galaxy population at the end of cosmic HI reionization (5.0 ≤ <jats:italic>z</jats:italic> ≤ 6.6) from a large sample of 49 galaxies with spectroscopically confirmed redshifts. We determine the rest-frame UV and Ly<jats:italic>α</jats:italic> luminosity functions and use them to calculate SFRD at the median redshift of our sample <jats:italic>z</jats:italic> = 5.6.</jats:p> <jats:p><jats:italic>Methods.</jats:italic> We selected a sample of galaxies at 5.0 ≤ <jats:italic>z</jats:italic><jats:sub>spec</jats:sub> ≤ 6.6 from the VUDS. We cleaned our sample from low redshift interlopers using ancillary photometric data. We identified galaxies with Ly<jats:italic>α</jats:italic> either in absorption or in emission, at variance with most spectroscopic samples in the literature where Ly<jats:italic>α</jats:italic> emitters (LAE) dominate. We determined luminosity functions using the 1/<jats:italic>V</jats:italic><jats:sub>max</jats:sub> method.</jats:p> <jats:p><jats:italic>Results.</jats:italic> The galaxies in this redshift range exhibit a large range in their properties. A fraction of our sample shows strong Ly<jats:italic>α</jats:italic> emission, while another fraction shows Ly<jats:italic>α</jats:italic> in 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 slope <jats:italic>α</jats:italic> = 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 Ly<jats:italic>α</jats:italic> luminosity function is best fitted with a Schechter function. We derive a logSFRD<jats:sub>UV</jats:sub>(<jats:italic>M</jats:italic><jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup> Mpc<jats:sup>−3</jats:sup>) = −1.45<jats:sup>+0.06</jats:sup><jats:sub>−0.08</jats:sub> and logSFRD<jats:sub>Ly<jats:italic>α</jats:italic></jats:sub>(<jats:italic>M</jats:italic><jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup> Mpc<jats:sup>−3</jats:sup>) = −1.40<jats:sup>+0.07</jats:sup><jats:sub>−0.08</jats:sub>. The SFRD derived from the Ly<jats:italic>α</jats:italic> luminosity function is in excellent agreement with the UV-derived SFRD after correcting for IGM absorption.</jats:p> <jats:p><jats:italic>Conclusions.</jats:italic> Our new SFRD measurements at a mean redshift of <jats:italic>z</jats:italic> = 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 at <jats:italic>z</jats:italic> > 2. The bright end of the Ly<jats:italic>α</jats:italic> luminosity 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 < <jats:italic>z</jats:italic> < 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.</jats:p>
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