The relationship between star formation rate and radio synchrotron luminosity at 0 < z < 2

TL;DR

This study investigates the link between star formation rates and radio synchrotron luminosity in galaxies up to redshift 2, testing if local relations hold at high redshift and exploring potential evolution.

Contribution

It provides new 610-MHz GMRT observations and demonstrates that the local SFR-radio luminosity relation applies to high-redshift, high-SFR galaxies with some exceptions.

Findings

The local SFR-radio luminosity relation is applicable up to z=2.

Some galaxies show deviations possibly due to recent starburst activity or measurement inaccuracies.

The physical processes behind synchrotron radiation have largely remained consistent since peak star formation.

Abstract

We probe the relationship between star formation rate (SFR) and radio synchrotron luminosity in galaxies at 0 < z < 2 within the northern Spitzer Wide-area Infrared Extragalactic survey (SWIRE) fields, in order to investigate some of the assumptions that go into calculating the star formation history of the Universe from deep radio observations. We present new 610-MHz Giant Metrewave Radio Telescope (GMRT) observations of the European Large-Area ISO Survey (ELAIS)-N2 field, and using this data, along with previous GMRT surveys carried out in the ELAIS-N1 and Lockman Hole regions, we construct a sample of galaxies which have redshift and SFR information available from the SWIRE survey. We test whether the local relationship between SFR and radio luminosity is applicable to z = 2 galaxies, and look for evolution in this relationship with both redshift and SFR in order to examine whether the physical processes which lead to synchrotron radiation have remained the same since the peak of star formation in the Universe. We find that the local calibration between radio luminosity and star formation can be successfully applied to radio-selected high-redshift, high-SFR galaxies, although we identify a small number of sources where this may not be the case; these sources show evidence for inaccurate estimations of their SFR, but there may also be some contribution from physical effects such as the recent onset of starburst activity, or suppression of the radio luminosity within these galaxies.