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Normal Galaxies in the Infrared

Helou, G. (2000) Normal Galaxies in the Infrared. In: Astronomie spatiale infrarouge, aujourd’hui et demain: Infrared space astronomy, today and tomorrow. Les Houches - Ecole d’Ete de Physique Theorique. No.70. Springer , Berlin, pp. 337-380. ISBN 978-3-540-67386-6.

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A normal galaxy is one that derives its luminosity primarily from nuclear burning in stars, and is at neither the high nor the low extreme of the luminosity distribution. In such galaxies, the visible and ultraviolet is the only direct window onto the photospheres of stars, whereas the rest of the spectrum reflects reprocessed light from stars (Fig. 1). Dust in the interstellar medium reprocesses part of the stellar luminosity into infrared emission from a few μm to 1 mm or longer wavelengths. The radio emission at millimeter wavelengths derives from thermal emission from ionized plasmas in HII regions, whereas the synchrotron emission from cosmic ray electrons (CR e⁻) trapped in the magnetic field of the galaxy fill in the cm-wavelength spectrum. In the X-rays, the luminosity is dominated by very hot plasmas at T ≳ 10 K⁶ created by shocks from supernova explosions. The global spectrum of normal galaxies has some very stable signatures, and other quite variable aspects. Much of this article is an attempt to understand what makes for stability in the spectrum, and what significance to attach to the variable parameters.

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Helou, G.0000-0003-3367-3415
Additional Information:© 2000 EDP Sciences, Springer-Verlag. First Online: 31 July 2002. I would like to thank the organizers of the Summer School for the invitation to participate in this exciting encounter, and for their patience when it came to submitting the manuscript. James Lequeux in addition provided help and comments on the manuscript. Danny Dale and Alessandra Contursi helped with customized plots, and a careful reading of the manuscript. This work was carried out at the California Institute of Technology, under funding by the National Aeronautics and Space Administration. It was supported in part by the ISO Data Analysis Funding Program, administered for NASA by the Jet Propulsion Laboratory, California Institute of Technology.
Funding AgencyGrant Number
Subject Keywords:Optical Depth; Star Formation; Star Formation Rate; Spectral Energy Distribution; Infrared Emission
Series Name:Les Houches - Ecole d’Ete de Physique Theorique
Issue or Number:70
Record Number:CaltechAUTHORS:20200615-163436555
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103934
Deposited By: Tony Diaz
Deposited On:22 Jun 2020 17:40
Last Modified:16 Nov 2021 18:26

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