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.

A Statistical and Multi-wavelength Study of Star Formation in Galaxies

“…We show in Table 3.5 as "method C" how the figures change using this alternative method. Indeed the measured boosting is smaller than when using the full PSF, and is consistent with that reported by Béthermin et al (2015b), but our method is even less affected thanks to the use of a local background.…”

“…It is however less versatile, and in particular it is not capable of measuring flux dispersions. Béthermin et al (2015b) also show that it can suffer from biases coming from the incompleteness of the input catalog.…”

The Herschel Bright Sources (HerBS): sample definition and SCUBA-2 observations

“…Typically, higher average redshifts are expected for longer selection wavelengths (Bethermin et al 2015). We see this for the SPT sample, which has higher average redshifts.…”

“…This increase is able to compensate for the cosmological dimming due to the increase of luminosity distance, e.g. a redshift 1 or 4 galaxy has a similar flux density in sub-mm wavelengths (Blain & Longair 1993;Blain et al 2002;Bethermin et al 2015).…”

Faint Submillimeter Galaxies Identified Through Their Optical/Near-Infrared Colors. I. Spatial Clustering and Halo Masses

“…Since recently both observations and theoretical models have suggested little variations of redshift distributions between bright and faint SMGs (e.g., Simpson et al 2014;Béthermin et al 2015;Cowley et al 2015), together with the fact that faint SMGs withS 1 850 mJy are about 5-10 times more abundant than bright SMGs, we expect the lifetime of faint SMGs to be longer than that of bright SMGs by a similar factor. Based on the clustering measurements and the estimated gas depletion timescale, the typical lifetime of bright SMGs is ∼100 Myr (e.g., Hickox et al 2012;Bothwell et al 2013).…”