Naslov
The VLA-COSMOS Perspective on the Infrared-Radio Relation. I. New Constraints on Selection Biases and the Non-Evolution of the Infrared/Radio Properties of Star-Forming and Active Galactic Nucleus Galaxies at Intermediate and High Redshift

Autori
Sargent, M.T. ; Schinnerer, E. ; Murphy, E. ; Aussel, H. ; Le Floc'h, E. ; Frayer, D.T. ; Martínez-Sansigre, A. ; Oesch, P. ; Salvato, M. ; Smolčić, Vernesa ; Zamorani, G. ; Brusa, M. ; Cappelluti, N. ; Carilli, C.L. ; Carollo, C.M. ; Ilbert, O. ; Kartaltepe, J. ; Koekemoer, A.M. ; Lilly, S.J. ; Sanders, D.B. ; Scoville, N.Z.

Izvornik
The Astrophysical journal. Supplement series (0067-0049) 186 (2010), 2; 341-377

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
cosmology: observations; galaxies: active; galaxies: evolution; galaxies: high-redshift; infrared: galaxies; radio continuum: galaxies; surveys

Sažetak
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 deg2 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 zin [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.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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