FOREGROUND CONTAMINATION IN Lyα INTENSITY MAPPING DURING THE EPOCH OF REIONIZATION

Abstract

The intensity mapping of Ly-alpha emission during the epoch of reionization\n(EoR) will be contaminated by foreground emission lines from lower redshifts.\nWe calculate the mean intensity and power spectrum of Ly-alpha emission at z~7,\nand estimate the uncertainties according to the relevant astrophysical\nprocesses. We find that the low-redshift emission lines from 6563 A H-alpha,\n5007 A [OIII] and 3727 A [OII] will be the strong contaminants on the observed\nLy-alpha power spectrum. We make use of both the star formation rate (SFR) and\nluminosity functions (LF) to estimate the mean intensity and power spectra of\nthe three foreground lines at z~0.5 for H-alpha, z~0.9 for [OIII] and z~1.6 for\n[OII], as they will contaminate the Ly-alpha emission at z~7. The [OII] line is\nfound to be the strongest. We analyze the masking of the bright survey pixels\nwith a foreground line above some line intensity threshold as a way to reduce\nthe contamination in the intensity mapping survey. We find that the foreground\ncontamination can be neglected if we remove the pixels with fluxes above\n1.4x10^-20 W/m^2.