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A Closer View of the Radio-FIR Correlation: Disentangling the Contributions of Star Formation and Active Galactic Nucleus Activity

Morić, I. and Smolčić, V. and Kimball, A. and Riechers, D. A. and Ivezić, Ž. and Scoville, N. (2010) A Closer View of the Radio-FIR Correlation: Disentangling the Contributions of Star Formation and Active Galactic Nucleus Activity. Astrophysical Journal, 724 (1). pp. 779-790. ISSN 0004-637X.

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We extend the Unified Radio Catalog, a catalog of sources detected by various (NVSS, FIRST, WENSS, GB6) radio surveys, and SDSS, to IR wavelengths by matching it to the IRAS Point and Faint Source catalogs. By fitting each NVSS-selected galaxy's NUV-NIR spectral energy distribution (SED) with stellar population synthesis models we add to the catalog star formation rates (SFRs), stellar masses, and attenuations. We further add information about optical emission-line properties for NVSS-selected galaxies with available SDSS spectroscopy. Using an NVSS 20 cm (F_(1.4 GHz) ≳ 2.5 mJy) selected sample, matched to the SDSS spectroscopic ("main" galaxy and quasar) catalogs and IRAS data (0.04 < z ≲ 0.2) we perform an in-depth analysis of the radio-FIR correlation for various types of galaxies, separated into (1) quasars, (2) star-forming, (3) composite, (4) Seyfert, (5) LINER, and (6) absorption line galaxies using the standard optical spectroscopic diagnostic tools. We utilize SED-based SFRs to independently quantify the source of radio and FIR emission in our galaxies. Our results show that Seyfert galaxies have FIR/radio ratios lower than, but still within the scatter of, the canonical value due to an additional (likely active galactic nucleus (AGN)) contribution to their radio continuum emission. Furthermore, IR-detected absorption and LINER galaxies are on average strongly dominated by AGN activity in both their FIR and radio emission; however their average FIR/radio ratio is consistent with that expected for star-forming galaxies. In summary, we find that most AGN-containing galaxies in our NVSS-IRAS-SDSS sample have FIR/radio flux ratios indistinguishable from those of the star-forming galaxies that define the radio-FIR correlation. Thus, attempts to separate AGNs from star-forming galaxies by their FIR/radio flux ratios alone can separate only a small fraction of the AGNs, such as the radio-loud quasars.

Item Type:Article
Related URLs:
URLURL TypeDescription
Smolčić, V.0000-0002-3893-8614
Riechers, D. A.0000-0001-9585-1462
Ivezić, Ž.0000-0001-5250-2633
Scoville, N.0000-0002-0438-3323
Additional Information:© 2010 American Astronomical Society. Received 2010 August 9; accepted 2010 September 21; published 2010 November 4. Based on observations with the National Radio Astronomy Observatory which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. We are grateful to the anonymous referee for helpful comments. The authors thank R. Beck, S. Charlot, O. Ilbert, K. K. Knudsen, M. Sargent, and J. Walcher for insightful discussions. I.M. thanks California Institute of Technology for generous hospitality. I.M. and D.R. acknowledge support from NASA through an award issued by JPL/Caltech. V.S. acknowledges support from the Owens Valley Radio Observatory, which is supported by the National Science Foundation through grant AST-0838260. V.S. and I.M. thank Unity through Knowledge Fund ( for collaboration support through the “Homeland Visit” grant. D.R. acknowledges support from NASA through Hubble Fellowship grant HST-HF-51235.01 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. A.K. and Z.I. acknowledge NSF grant AST-0507259 to the University of Washington. The research leading to these results has received funding from the European Union’s Seventh Framework program under grant agreement 229517. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web Site is The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington.
Funding AgencyGrant Number
Owens Valley Radio ObservatoryUNSPECIFIED
Unity through Knowledge FundUNSPECIFIED
NASA Hubble FellowshipHST-HF-51235.01
Space Telescope Science InstituteUNSPECIFIED
European Union’s Seventh Framework program229517
Subject Keywords:cosmology: observations; evolution; galaxies: active; galaxies: fundamental parameters; radio continuum: galaxies
Issue or Number:1
Classification Code:PACS: 95.80.+p; 98.62.Ai; 98.54.Cm; 98.62.Lv; 98.62.Qz
Record Number:CaltechAUTHORS:20101207-140605345
Persistent URL:
Official Citation:I. Morić et al 2010 ApJ 724 779 doi: 10.1088/0004-637X/724/1/779
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21220
Deposited By: Jason Perez
Deposited On:08 Dec 2010 19:45
Last Modified:03 Oct 2019 02:21

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