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Published April 1, 2016 | Published + Submitted
Journal Article Open

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


The aim of this paper is to investigate spectral and photometric properties of 854 faint (i_(AB) ≲ 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 E_s(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 (SFG_N; EW ≤ 0 Å), SFGs with Lyα emission (SFG_L; 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 SFG_N, SFG_L 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 (m_(3.6) ≲ 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.

Additional Information

© 2016 ESO. Received 3 March 2015. Accepted 11 December 2015. We thank the referee for helpful comments and suggestions that significantly improved this paper. This work is supported by funding from the European Research Council Advanced Grant ERC-2010-AdG-268107-EARLY and by INAF Grants PRIN 2010, PRIN 2012 and PICS 2013. A.C., O.C., M.T. and V.S. acknowledge the grant MIUR PRIN 2010–2011. This work is based on data products made available at the CESAM data center, Laboratoire d'Astrophysique de Marseille. This work partly uses observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS.

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Published - aa26012-15.pdf

Submitted - 1503.01753v2.pdf


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