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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 559439.0, MPI für Astronomie / Publikationen_mpia
The VLA-COSMOS perspective on the IR-radio relation. I. New constraints on selection biases and the non-evolution of the IR/Radio properties of star forming and AGN galaxies at intermediate and high redshift
Authors:Sargent, Mark T.; Schinnerer, E.; Murphy, E.; Aussel, H.; Le Floc'h, E.; Frayer, D. T.; Martínez-Sansigre, A.; Oesch, P.; Salvato, M.; Smolcic, V.; Zamorani, G.; Brusa, M.; Cappelluti, N.; Carollo, C. M.; Ilbert, O.; Kartaltepe, J.; Koekemoer, A. M.; Lilly, S. J.; Sanders, D. B.; Scoville, N. Z.
Date of Publication (YYYY-MM-DD):2010
Title of Journal:The Astrophysical Journal Supplement Series
Issue / Number:2
Start Page:341
End Page:377
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:VLA 1.4 GHz (rms noise ~0.012 mJy) and MIPS 24 and 70 micron (rms noise ~0.02 and ~1.7 mJy, respectively) observations covering the 2 square degree COSMOS field are combined with an extensive multi-wavelength data set to study the evolution of the 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 (q24 & q70), as well as the ratio of the total IR and the 1.4 GHz luminosity (qTIR) are used as indicators for the IR/radio properties of star forming galaxies and AGN. 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 2.5<z<5. At redshift z<1.4 we observe that radio-quiet AGN 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.
Free Keywords:Astrophysics - Cosmology and Extragalactic Astrophysics
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:URL:http://adsabs.harvard.edu/abs/2010arXiv1001.1354S [ID No:1]
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