THE CLOWES-CAMPUSANO LARGE QUASAR GROUP SURVEY. I.GALEXSELECTED SAMPLE OF LYMAN BREAK GALAXIES ATz∼ 1

Abstract

The nature of galaxy structures on large scales is a key observational prediction for current models of galaxy formation. The Sloan Digital Sky Survey (SDSS) and the 2dF galaxy survey have revealed a number of structures on 40-150 h(-1) Mpc scales at low redshifts, and some even larger ones. To constrain galaxy number densities, luminosities, and stellar populations in large structures at higher redshift, we have investigated two sheet-like structures of galaxies at z = 0.8 and 1.3 spanning 150 h(-1) comoving Mpc embedded in large quasar groups (LQGs) extending over at least 200 h(-1) Mpc. We present first results of an analysis of these sheet-like structures using two contiguous 1 deg Galaxy Evolution Explorer (GALEX) fields (FUV and NUV) cross-correlated with optical data from the SDSS. We derive a sample of 462 Lyman break galaxy (LBG) candidates coincident with the sheets. Using the GALEX and SDSS data, we show that the overall average spectral energy distribution of a LBG galaxy at z similar to 1 is flat (in f(lambda)) in the rest-frame wavelength range from 1500 angstrom to 4000 angstrom, implying evolved populations of stars in the LBGs. From the luminosity functions we get indications for overdensities in the two LQGs compared to their foreground regions. Similar conclusions come from the calculation of the 2-point correlation function, showing a 2 sigma overdensity for the LBGs in the z similar to 0.8 LQG on scales of 1.6 to 4.8 Mpc, indicating similar correlation scales for our LBG sample as their z similar to 3 counterparts.