The dust un-biased cosmic star formation history from the 20 cm VLA-COSMOS survey

TL;DR

This study uses a large radio-selected galaxy sample from the VLA-COSMOS survey to accurately trace the cosmic star formation history up to redshift 1.3, confirming a significant decline since z~1.

Contribution

It provides the first detailed measurement of the high-luminosity end of the star-forming galaxy luminosity function using radio data, differentiating AGN from star formation, and confirms the decline in star formation rate density.

Findings

Slower evolution of high-luminosity star-forming galaxies than previously thought.

More intense star formation in luminous starbursts at higher redshift.

Radio data independently confirms the decline in cosmic star formation since z~1.

Abstract

We derive the cosmic star formation history (CSFH) out to z=1.3 using a sample of ~350 radio-selected star-forming galaxies, a far larger sample than in previous, similar studies. We attempt to differentiate between radio emission from AGN and star-forming galaxies, and determine an evolving 1.4 GHz luminosity function based on these VLA-COSMOS star forming galaxies. We precisely measure the high-luminosity end of the star forming galaxy luminosity function (SFR>100 M_Sol/yr; equivalent to ULIRGs) out to z=1.3, finding a somewhat slower evolution than previously derived from mid-infrared data. We find that more stars are forming in luminous starbursts at high redshift. We use extrapolations based on the local radio galaxy luminosity function; assuming pure luminosity evolution, we derive $L_* \propto (1+z)^{2.1 \pm 0.2}$ or $L_* \propto (1+z)^{2.5 \pm 0.1}$, depending on the choice of the local radio galaxy luminosity function. Thus, our radio-derived results independently confirm the ~1 order of magnitude decline in the CSFH since z~1.