The Stochastic Effect of Ly-alpha absorbers on Broadband Luminosities of Galaxies

Abstract

We investigate the variations of broadband luminosities of low and intermediate redshift galaxies due to the stochastic nature of the neutral hydrogen present in form of Ly-alpha absorbers in the intergalactic medium. This effect is caused by variations in the distribution and properties (redshift, column density, Doppler parameter) of the absorbers along different lines-of-sight out to a given redshift. Using a set of observationally constrained redshift-, column density- and Doppler parameter distributions we perform Monte Carlo simulations for a large number of lines-of-sight towards galaxies at a given redshift z and calculate attenuated FUV/NUV magnitudes and corresponding 1-, 2- and 3-sigma variations. We predict significant variations in luminosity ranging from -0.22 to +0.48 magnitudes at the 1-sigma level for galaxies at z=1.5 in GALEX data.