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          Institute: MPI für Kernphysik     Collection: Infrared Astrophysics     Display Documents

ID: 204745.0, MPI für Kernphysik / Infrared Astrophysics
Modelling the pan-spectral energy distribution of starburst galaxies: I. The role of the ISM pressure and the molecular cloud dissipation timescale
Authors:Dopita, M. A.; Groves, B. A.; Fischera, J.; Sutherland, R. S.; Tuffs, R. J.; Popescu, C. C.; Kewley, L. J.; Reuland, M.; Leitherer, C.
Research Context:dust
Date of Publication (YYYY-MM-DD):2005-02-01
Title of Journal:Astrophysical Journal
Journal Abbrev.:ApJ
Issue / Number:2 part 1
Start Page:755
End Page:778
Copyright:© 2005. The American Astronomical Society
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:In this paper, we combine the stellar spectral synthesis code STARBURST99, the nebular modeling code MAPPINGS IIIq, a one-dimensional dynamical evolution model of H II regions around massive clusters of young stars, and a simplified model of synchrotron emissivity to produce purely theoretical self-consistent synthetic spectral energy distributions (SEDs) for (solar metallicity) starbursts lasting ± 108 yr. These SEDs extend from the Lyman limit to beyond 21 cm. We find that two ISM parameters control the form of the SED: the pressure in the diffuse phase of the ISM (or, equivalently, its density), and the molecular cloud dissipation timescale. In particular, the shape of the far-infrared (dust re-emission) bump is strongly dependent on the mean pressure in the star-forming or starburst galaxy. This can explain the range of far-infrared (FIR) colors seen in starburst galaxies. In the case of objects of composite excitation, such diagrams potentially provide a means of estimating the fraction of the FIR emission that is contributed by an active nucleus. We present detailed SED fits to Arp 220 and NGC 6240, and we give the predicted colors for starburst galaxies derived from our models for the IRAS and the Spitzer Space Telescope MIPS and IRAC instruments. Our models reproduce the spread in observed colors of starburst galaxies. From both the SED fits and the color : color diagrams, we infer the presence of a population of compact and ultracompact H II regions around single OB stars or small OB clusters. Finally, we present absolute calibrations to convert observed fluxes into star formation rates in the UV (GALEX), at optical wavelengths (H), and in the IR (IRAS or Spitzer). We show that 25 m fluxes are particularly valuable as star formation indicators, since they largely eliminate one of the parameters controlling the IR SED.
Free Keywords:dust, extinction-galaxies: general-galaxies: starburst-H II regions - infrared: galaxies - radio continuum: galaxies - ultraviolet: galaxies
External Publication Status:published
Document Type:Article
Affiliations:MPI für Kernphysik/Group H. J. Völk/Infrared Astrophysics (R. Tuffs, H.J. Völk)
External Affiliations:Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston Creek, ACT 2611, Australia
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138
Sterrewacht Leiden, P.O. Box 9513, 2300 RA Leiden, Netherlands
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218
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