Evolution of the Far-Infrared-Radio Correlation and Infrared SEDs of Massive Galaxies over z = 0 - 2

TL;DR

This study examines the evolution of the far-infrared-radio correlation in massive galaxies from redshift 0 to 2, revealing that the correlation remains stable when using certain wavelengths, but shows signs of change at others, indicating evolving galaxy properties.

Contribution

It provides new insights into the SEDs of high-redshift galaxies, showing a preference for quiescent spiral templates and highlighting potential spectral changes affecting the FRC at z=0-2.

Findings

FRC index remains stable from z=0 to 2 with certain photometry

High-redshift galaxies are best fit by quiescent spiral SEDs

Possible spectral steepening or deficiency at 70μm at high z

Abstract

We investigate the far-infrared-radio correlation (FRC) of stellar-mass-selected galaxies in the Extended Chandra Deep Field South using far-infrared imaging from Spitzer and radio imaging from the Very Large Array and Giant Metre-Wave Radio Telescope. We stack in redshift bins to probe galaxies below the noise and confusion limits. Radio fluxes are K-corrected using observed flux ratios, leading to tentative evidence for an evolution in spectral index. We compare spectral energy distribution (SED) templates of local galaxies for K-correcting FIR fluxes, and show that the data are best fit by a quiescent spiral template (M51) rather than a warm starburst (M82) or ULIRG (Arp220), implying a predominance of cold dust in massive galaxies at high redshift. In contrast we measure total infrared luminosities that are consistent with high star-formation rates. We observe that the FRC index (q) does not evolve significantly over z=0-2 when computed from K-corrected 24 or 160-mum photometry, but that using 70-mum fluxes leads to an apparent decline in q beyond z~1. This suggests some change in the SED at high redshift, either a steepening of the spectrum at rest-frame ~25-35mum or a deficiency at ~70mum leading to a drop in the total infrared/radio ratios. We compare our results to other work in the literature and find synergies with recent findings on the high-redshift FRC, high specific star-formation rates of massive galaxies and the cold dust temperatures in these galaxies.