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

N. P. Hathi, O. Le Fèvre, O. Ilbert, P. Cassata, L. A. M. Tasca, B. C. Lemaux, B. Garilli, V. Le Brun, D. Maccagni, L. Pentericci, E. Vanzella, G. Zamorani, E. Zucca, R. Amorín, S. Bardelli, L. P. Cassarà, M. Castellano, A. Cimatti, O. Cucciati, A. DurkalecA. Fontana, M. Giavalisco, A. Grazian, L. Guaita, A. Koekemoer, S. Paltani, J. Pforr, B. Ribeiro, D. Schaerer, M. Scodeggio, V. Sommariva, M. Talia, L. Tresse, D. Vergani, P. Capak, S. Charlot, T. Contini, J. G. Cuby, S. de la Torre, J. Dunlop, S. Fotopoulou, C. López-Sanjuan, Y. Mellier, M. Salvato, N. Scoville, Y. Taniguchi, P. W. Wang

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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.
Original languageEnglish
JournalAstronomy & Astrophysics
Publication statusPublished - 1 Apr 2016


  • galaxies: evolution
  • galaxies: formation
  • galaxies: high-redshift


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