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For refcode 2002ApJ...572..105S:
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2002ApJ...572..105S The Far-Infrared Energy Distributions of Seyfert and Starburst Galaxies in the Local Universe: Infrared Space Observatory Photometry of the 12 Micron Active Galaxy Sample Luigi Spinoglio Istituto di Fisica dello Spazio Interplanetario, CNR via Fosso del Cavaliere 100, I-00133 Rome, Italy; luigi@ifsi.rm.cnr.it Paola Andreani Osservatorio Astronomico Padova, Vicolo dell'Osservatorio 5, I-35122 Padova, Italy; andreani@pd.astro.it and Matthew A. Malkan Physics and Astronomy Department, UCLA, Los Angeles, CA 90095-1562; malkan@astro.ucla.edu Received 2001 November 19; accepted 2002 February 18 ABSTRACT New far-infrared photometry with ISOPHOT aboard the Infrared Space Observatory (ISO) is presented for 58 galaxies with homogeneous published data for another 32 galaxies, all belonging to the 12 micron galaxy sample - in total, 29 Seyfert 1 galaxies, 35 Seyfert 2 galaxies, and 12 starburst galaxies, or about half of the 12 micron active galaxy sample, plus 14 normal galaxies for comparison. ISO and Infrared Astronomical Satellite (IRAS) data are used to define color-color diagrams and spectral energy distributions (SEDs). Thermal dust emission at two temperatures (one cold at 15-30 K and one warm at 50-70 K) can fit the 60-200 micron SED, with a dust emissivity law proportional to the inverse square of the wavelength. Seyfert 1 galaxies and Seyfert 2 galaxies are indistinguishable longward of 100 microns, while, as already seen by IRAS, the former have flatter SEDs shortward of 60 microns. A mild anticorrelation is found between the [200-100] color and the "60 micron excess." We infer that this is due to the fact that galaxies with a strong starburst component and thus a strong 60 micron flux have a steeper far-infrared turnover. In non-Seyfert galaxies, increasing the luminosity corresponds to increasing the star formation rate, which enhances the 25 and 60 micron emission. This shifts the peak emission from around 150 microns in the most quiescent spirals to shorter than 60 micron in the strongest starburst galaxies. To quantify these trends further, we identified with the IRAS colors three idealized infrared SEDs: pure quiescent disk emission, pure starburst emission, and pure Seyfert nucleus emission. Even between 100 and 200 micron, the quiescent disk emission remains much cooler than the starburst component. Seyfert galaxies have 100-200 micron SEDs ranging from pure disks to pure starbursts, with no apparent contribution from their active nuclei at those wavelengths. Subject headings: galaxies: active - galaxies: nuclei - galaxies: photometry - galaxies: Seyfert - galaxies: starburst - infrared: galaxies
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