Identification of low luminosity high redshift galaxies using galaxy clusters as cosmic telescopes

Abstract

Current models of structure formation suggest that the first galaxies formed at z > 10 when the universe was < 500 Myr old. The detection and characterization of galaxies at these early epochs is therefore critical to estimate the star formation rate density and their contribution to the reionization. The CLASH project (Cluster Lensing And Supernova survey with Hubble) combines an HST Treasury program to obtain panchromatic (ACS + WFC3) imaging of 25 carefully selected massive clusters, with other multi-wavelength observations, including a large spectroscopic campaign with VLT/VIMOS. Gravitational lensing, which is particularly powerful in several CLASH clusters, boost the efficiency of finding low-luminosity (i.e. L < L*) galaxies, which are thought to play a critical role in reionizing the Universe beyond z ∼ 10. In this letter, we will give some highlights of the construction of a sample of ∼ 200 magnified lensed galaxies at 2 < z < 7, collected as part of the CLASH-VLT project, whose spectro-photometric data can be used to characterize the physical properties of the low-luminosity galaxy population at high-z.