THE SPITZER VIEW OF FR I RADIO GALAXIES: ON THE ORIGIN OF THE NUCLEAR MID-INFRARED CONTINUUM
- Department of Physics, University of California, Santa Barbara, CA 93106 (United States)
- Spitzer Science Center, California Institute of Technology, Mail Code 220-6, Pasadena, CA 91125 (United States)
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.
- OSTI ID:
- 21319596
- Journal Information:
- Astrophysical Journal, Vol. 701, Issue 2; Other Information: DOI: 10.1088/0004-637X/701/2/891; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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