The Spitzer View of FR I Radio Galaxies: On the Origin of the Nuclear Mid-Infrared Continuum
- Creators
- Leipski, C.
- Antonucci, R.
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Ogle, P.
- Whysong, D.
Abstract
We present Spitzer mid-infrared (MIR) spectra of 25 FR I radio galaxies and investigate the nature of their MIR continuum emission. MIR spectra of star-forming galaxies and quiescent elliptical galaxies are used to identify host galaxy contributions while radio/optical core data are used to isolate the nuclear nonthermal emission. Out of the 15 sources with detected optical compact cores, four sources are dominated by emission related to the host galaxy. Another four sources show signs of warm, nuclear dust emission: 3C15, 3C84, 3C270, and NGC 6251. It is likely that these warm dust sources result from hidden active galactic nuclei of optical spectral type 1. The MIR spectra of seven sources are dominated by synchrotron emission, with no significant component of nuclear dust emission. In parabolic spectral energy distribution fits of the nonthermal cores FR Is tend to have lower peak frequencies and stronger curvature than blazars. This is roughly consistent with the common picture in which the core emission in FR Is is less strongly beamed than in blazars.
Additional Information
© 2009 American Astronomical Society. Print publication: Issue 2 (2009 August 20); received 2008 October 6; accepted for publication 2009 June 11; published 2009 July 28. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. We have also made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. We thank Ann Wehrle for a critical reading of a previous version of this paper, and also Alan Marscher and Luis Ho for advice on specific issues.We are grateful to Marco Chiaberge for comments on a previous version of the paper and for newly measuring the optical compact core flux of 3C15. We are thankful for the critical comments of the referee which helped to improve the paper. This research has made use of Sloan Digital Sky Survey (SDSS) data products. 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 http://www.sdss.org/. Facility: Spitzer (IRS)Attached Files
Published - Leipski2009p5709Astrophys_J.pdf
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Additional details
- Eprint ID
- 15418
- Resolver ID
- CaltechAUTHORS:20090828-133716201
- NASA
- Alfred P. Sloan Foundation
- NSF
- Department of Energy (DOE)
- Japanese Monbukagakusho
- Max Planck Society
- Higher Education Funding Council for England
- Created
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2009-08-28Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field