The VIMOS Ultra Deep Survey: Lyα emission and stellar populations of star-forming galaxies at 2 < z < 2.5

Journal
Date Issued
2016
Author(s)
Hathi, N. P.
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Le Fèvre, O.
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Ilbert, O.
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Cassata, P.
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Tasca, L. A. M.
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Lemaux, B. C.
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Le Brun, V.
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Maccagni, D.
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Thomas, R.
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Zamorani, G.
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Amorín, R.
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•
•
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Cimatti, A.
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Durkalec, A.
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Giavalisco, M.
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Guaita, L.
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Koekemoer, A.
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Paltani, S.
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Pforr, J.
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Ribeiro, B.
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Schaerer, D.
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Sommariva, V.
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Talia, M.
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Tresse, L.
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Capak, P.
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Charlot, S.
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Contini, T.
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Cuby, J. G.
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Dunlop, J.
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Fotopoulou, S.
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López-Sanjuan, C.
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Mellier, Y.
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Salvato, M.
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Scoville, N.
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Taniguchi, Y.
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Wang, P. W.
DOI
Abstract
The aim of this paper is to investigate spectral and photometric properties of 854 faint (IAB ≲ 25 mag) star-forming galaxies (SFGs) at 2 < z < 2.5 using the VIMOS Ultra-Deep Survey (VUDS) spectroscopic data and deep multi-wavelength photometric data in three extensively studied extragalactic fields (ECDFS, VVDS, COSMOS). These SFGs were targeted for spectroscopy as a result of their photometric redshifts. The VUDS spectra are used to measure the UV spectral slopes (β) as well as Lyα equivalent widths (EW). On average, the spectroscopically measured β (-1.36 ± 0.02), is comparable to the photometrically measured β (-1.32 ± 0.02), and has smaller measurement uncertainties. The positive correlation of β with the spectral energy distribution (SED)-based measurement of dust extinction Es(B-V) emphasizes the importance of β as an alternative dust indicator at high redshifts. To make a proper comparison, we divide these SFGs into three subgroups based on their rest-frame Lyα EW: SFGs with no Lyα emission (SFGN; EW ≤ 0 Å), SFGs with Lyα emission (SFGL; EW > 0 Å), and Lyα emitters (LAEs; EW ≥ 20 Å). The fraction of LAEs at these redshifts is ~10%, which is consistent with previous observations. We compared best-fitSED-estimated stellar parameters of the SFGN, SFGL and LAE samples. For the luminosities probed here (~ L∗), we find that galaxies with and without Lyα in emission have small but significant differences in their SED-based properties. We find that LAEs have less dust, and lower star-formation rates (SFR) compared to non-LAEs. We also find that LAEs are less massive compared to non-LAEs, though the difference is smaller and less significant compared to the SFR and Es(B-V). When we divide the LAEs according to their Spitzer/IRAC 3.6 μm fluxes, we find that the fraction of IRAC-detected (m3.6 ≲ 25 mag) LAEs is much higher than the fraction of IRAC-detected narrow band (NB)-selected LAEs at z ≃ 2-3. This could imply that UV-selected LAEs host a more evolved stellar population, which represents a later stage of galaxy evolution, compared to NB-selected LAEs.

Based on data obtained with the European Southern Observatory Very Large Telescope, Paranal, Chile, under Large Program 185.A-0791.

Volume
588
Start page
A26
Uri
Url
Issn Identifier
0004-6361
Ads BibCode
2016A&A...588A..26H
Rights
open.access
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