The influence of wavelength, flux, and lensing selection effects on the redshift distribution of dusty, star-forming galaxies

Abstract : We interpret the wide variety of redshift distributions for galaxies found by far-infrared and (sub) millimeter deep surveys depending on their depth and wavelength using our phenomenological model of galaxy evolution. This model reproduces the observed redshift distributions from 100 μm to 1.4 mm and, especially, the increase in the median redshift with survey wavelength without any new parameter tuning. This median redshift also varies significantly with the depth of the surveys, and deeper surveys do not necessarily probe higher redshifts. Paradoxically, at a fixed wavelength and flux limit, the lensed sources are not always at higher redshift. We found that the higher redshift of 1.4 mm-selected South Pole Telescope (SPT) sources compared to other SMG surveys is caused not only by the lensing selection, but also by the longer wavelength. This SPT sample is expected to be dominated by a population of lensed main-sequence galaxies and a minor contribution (~10%) of unlensed extreme starbursts.