A multi-wavelength study of z = 3.15 Lyman-α emitters in the GOODS South Field

Abstract

Context: Lyα-emitters have proven to be excellent probes of faint, star-forming galaxies in the high redshift universe. However, although the sample of known emitters is increasingly growing, their nature (e.g. stellar masses, ages, metallicities, star-formation rates) is still poorly constrained.
Aims: We aim to study the nature of Lyα-emitters, to find the properties of a typical Lyα-emitting galaxy and to compare these properties with the properties of other galaxies at similar redshift, in particular Lyman-break galaxies.
Methods: We have performed narrow-band imaging at the VLT, focused on Lyα at redshift z ≈ 3.15, in the GOODS-S field. We have identified a sample of Lyα-emitting candidates, and we have studied their Spectral Energy Distributions (SEDs).
Results: We find that the emitters are best fit by an SED with low metallicity (Z/Z⊙ = 0.005), low dust extinction (A_V ≈ 0.26) and medium stellar masses of approximately 10⁹ M_⊙. The age is not very well constrained. One object out of 24 appears to be a high redshift Lyα-emitting dusty starburst galaxy. We find filamentary structure as traced by the Lyα-emitters at the 4σ level. The rest-frame UV SED of these galaxies is very similar to that of Lyman Break Galaxies (LBGs) and comply with the selection criteria for U-band drop-outs, except they are intrinsically fainter than the current limit for LBGs.
Conclusions: Lyα-emitters are excellent probes of galaxies in the distant universe, and represent a class of star-forming, dust and AGN free, medium mass objects.

Based on observations carried out at the European Southern Observatory (ESO) under prog. ID No. 70.A-0447, 274.A-5029 and LP168.A-0485.