2010/01/11 by M. Sargent, Mark T. Sargent, E. Schinnerer +27 · 1 citation
Physics and Astronomy · #Active galactic nucleus #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gamma-ray bursts and supernovae #Infrared #Luminosity #Luminous infrared galaxy #Physics #Radio galaxy #Redshift #Star formation #astro-ph.CO
paper · pdf · doi:10.1088/0067-0049/186/2/341
52 pages, 23 figures (11 at reduced resolution). Accepted for publication in ApJS
arxiv created 2010/01/11 · openalex publication_date 2010/01/28 · arxiv updated 2015/05/14 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
VLA 1.4 GHz (σ∼ 0.012 mJy) and MIPS 24 and 70 μm (σ∼ 0.02 and 1.7 mJy, respectively) observations covering the 2 deg 2 COSMOS field are combined with an extensive multiwavelength data set to study the evolution of the infrared (IR)–radio relation at intermediate and high redshift. With ∼4500 sources—of which ∼30% have spectroscopic redshifts—the current sample is significantly larger than previous ones used for the same purpose. Both monochromatic IR/radio flux ratios ( q 24 and q 70 ), as well as the ratio of the total IR and the 1.4 GHz luminosity ( q TIR ), are used as indicators for the IR/radio properties of star-forming galaxies and active galactic nuclei (AGNs). Using a sample jointly selected at IR and radio wavelengths in order to reduce selection biases, we provide firm support for previous findings that the IR–radio relation remains unchanged out to at least z ∼ 1.4. Moreover, based on data from ∼150 objects we also find that the local relation likely still holds at z ∈ [2.5, 5]. At redshift z < 1.4, we observe that radio-quiet AGNs populate the locus of the IR–radio relation in similar numbers as star-forming sources. In our analysis, we employ the methods of survival analysis in order to ensure a statistically sound treatment of flux limits arising from non-detections. We determine the observed shift in average IR/radio properties of IR- and radio-selected populations and show that it can reconcile apparently discrepant measurements presented in the literature. Finally, we also investigate variations of the IR/radio ratio with IR and radio luminosity and find that it hardly varies with IR luminosity but is a decreasing function of radio luminosity.