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Date and Time of the Query: 2019-04-25 T18:40:42 PDT
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For refcode 1989MNRAS.238..523R:
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Copyright by Royal Astronomical Society. 1989MNRAS.238..523R Models for infrared emission from IRAS galaxies M. Rowan-Robinson and J. Crawford Astronomy Unit, Queen Mary College, Mile End Road, London E1 4NS Accepted 1988 November 24. Received 1988 November 23; in original form 1986 June 17 Summary. The far-infrared (10-100 microns) spectra of galaxies detected in all four wavelength bands by IRAS are modelled in terms of three components: a cool 'disc' component; a warmer 'starburst' component, and a 'Seyfert' component peaking at 25 microns. The luminosity in the 'disc' component is well-correlated with the optical luminosity of the galaxy and this component is interpreted as emission from interstellar dust illuminated by the galaxy's starlight. The 'starburst' component is interpreted as being due to a burst of star formation in the galaxy nucleus and its spectrum is fitted well by a model consisting of hot stars embedded in an optically thick dust cloud. The 'seyfert' component is interpreted as being due to a power-law continuum source within a dust cloud presumably associated with the narrow-line region of the compact source. The density distribution in this dust cloud behaves as n(r) is proportional to r^-1^. The luminosity in the 'starburst' component is correlated with Hubble type and whether or not the galaxy has a bar. The luminosity in the 'Seyfert' component is correlated with the X-ray luminosity of the galaxy, supporting the hypothesis that the central compact power-law continuum source is responsible for illuminating the dust seen emitting in the far-infrared. Detailed ultraviolet to submillimetre spectra of several galaxies are compared with the predictions of the models. For the non-Seyfert and many of the Seyferts the proposed models are a good fit, but for NGC 1068 and several other Seyfert galaxies a more complex geometry for the dust distribution is indicated. The observed 1-10 micron spectra can be fitted in several cases with a higher-optical-depth 'Seyfert' component, but since a power-law continuum is seen in the ultraviolet for many of these Seyferts, we infer that the dust in the narrow-line region has a non-spherically symmetric geometry, for example being concentrated into clouds. For Arp 220 and NGC 4418, 'starburst' models with additional internal or interstellar extinction give a good fit, though a deeply dust-embedded quasar is also a possibility for Arp 220.
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