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

¹ European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching bei München, Germany e-mail: kim@dark-cosmology.dk
² Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
³ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85741 Garching bei München, Germany
⁴ European Southern Observatory, Alonso de Córdova 3107, Casilla 19001, Vitacura, Santiago 19, Chile

Received: 15 December 2006
Accepted: 7 June 2007

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 . 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.