Volume 588, April 2016
|Number of page(s)||18|
|Published online||14 March 2016|
The VIMOS Ultra Deep Survey: Lyα emission and stellar populations of star-forming galaxies at 2 < z < 2.5⋆
1 Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
2 INAF–Osservatorio Astronomico di Bologna, via Ranzani,1, 40127 Bologna, Italy
3 INAF–IASF, via Bassini 15, 20133 Milano, Italy
4 INAF–Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy
5 University of Bologna, Department of Physics and Astronomy (DIFA), V.le Berti Pichat, 6/2 – 40127 Bologna, Italy
6 INAF–IASF Bologna, via Gobetti 101, 40129 Bologna, Italy
7 Institut d’Astrophysique de Paris, UMR7095 CNRS, Université Pierre et Marie Curie, 98 bis Boulevard Arago, 75014 Paris, France
8 Institut de Recherche en Astrophysique et Planétologie – IRAP, CNRS, Université de Toulouse, UPS-OMP, 14, avenue E. Belin, 31400 Toulouse, France
9 Department of Astronomy, University of Geneva, ch. d’Écogia 16, 1290 Versoix, Switzerland
10 Geneva Observatory, University of Geneva, ch. des Maillettes 51, 1290 Versoix, Switzerland
11 Centro de Estudios de Física del Cosmos de Aragón, 44001 Teruel, Spain
12 Department of Astronomy, California Institute of Technology, 1200 E. California Blvd., MC 249–17, Pasadena, CA 91125, USA
13 Astronomy Department, University of Massachusetts, Amherst, MA 01003, USA
14 Max-Planck-Institut für Extraterrestrische Physik, Postfach 1312, 85741 Garching bei München, Germany
15 Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho 2–5, 790-8577 Matsuyama, Japan
16 SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, EH9 3HJ, UK
17 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
18 Instituto de Fisica y Astronomia, Facultad de Ciencias, Universidad de Valparaiso, Av. Gran Bretana 1111, Casilla 5030, Valparaiso, Chile
Received: 3 March 2015
Accepted: 11 December 2015
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.
Key words: galaxies: evolution / galaxies: formation / galaxies: high-redshift
© ESO, 2016
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