The VIMOS Ultra Deep Survey: Lyman Alpha Emission and Stellar Populations of Star-Forming Galaxies at 2<z<6

TL;DR

This study analyzes a large sample of star-forming galaxies at redshifts 2-6, revealing how Lyman alpha emission correlates with dust content, stellar properties, and redshift, highlighting the importance of sample selection effects.

Contribution

It provides a comprehensive analysis of Lyman alpha emitters across a wide redshift range using deep spectroscopic and photometric data, emphasizing the dependence of galaxy properties on selection methods.

Findings

LAE fraction increases from 10% at z~2 to 40% at z~5-6

LAEs have lower dust extinction (E(B-V)) than non-LAEs at all redshifts

LAEs tend to have slightly lower SFRs and stellar masses compared to non-LAEs

Abstract

The extensive ground-based spectroscopy campaign from the VIMOS Ultra-Deep Survey (VUDS), and the deep multi-wavelength photometry in three very well observed extragalactic fields (ECDFS, COSMOS, VVDS), allow us to investigate physical properties of a large sample (~4000 galaxies) of spectroscopically confirmed faint (i_{AB}<~25 mag) star-forming galaxies, with and without Lyman alpha in emission, at z~2-6. The fraction of Lyman alpha emitters (LAEs; equivalent width (EW)=>20A) increases from ~10% at z~2 to ~40% at z~5-6, which is consistent with previous studies that employ higher Lyman alpha EW cut. This increase in the LAE fraction could be, in part, due to a decrease in the dust content of galaxies as redshift increases. When we compare best-fit SED estimated stellar parameters for LAEs and non-LAEs, we find that E(B-V) is smaller for LAEs at all redshifts and the difference in the median E(B-V) between LAEs and non-LAEs increases as redshift increases, from 0.05 at z~2 to 0.1 at z~3.5 to 0.2 at z~5-6. For the luminosities probed here (~L*), we find that star formation rates (SFRs) and stellar masses of galaxies, with and without Lyman alpha in emission, show small differences such that, LAEs have lower SFRs and stellar masses compared to non-LAEs. This result could be a direct consequence of the sample selection. Our sample of LAEs are selected based on their continuum magnitudes and they probe higher continuum luminosities compared to narrow-band/emission line selected LAEs. Based on our results, it is important to note that all LAEs are not universally similar and their properties are strongly dependent on the sample selection, and/or continuum luminosities.