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The Mid-Infrared Properties of Starburst Galaxies from Spitzer-IRS Spectroscopy
The Astrophysical Journal (2006)
  • B. R. Brandl, Leiden University
  • J. Bernard-Salas, Cornell University
  • H. W. W. Spoon, Cornell University
  • D. Devost, Cornell University
  • G. C. Sloan, Cornell University
  • S. Guilles, Cornell University
  • Y. Wu, Cornell University
  • J. R. Houck, Cornell University
  • D. W. Weedman, Cornell University
  • L. Armus, California Institue of Technology
  • P. N. Appleton, Southern California Institute of Technology
  • B. T. Soifer, California Institute of Technology
  • V. Charmandaris, University of Crete
  • L. Hao, Cornell University
  • Sarah J.U. Higdon, Cornell University
  • J. A. Marshall, Cornell University
  • T. L. Herter, Cornell University
We present 5Y38 m mid-infrared spectra at a spectral resolution of R  65Y130 of a large sample of 22 starburst nuclei taken with the Infrared Spectrograph ( IRS) on board the Spitzer Space Telescope. The spectra show a vast range of starburst SEDs. The silicate absorption ranges from essentially no absorption to heavily obscured systems with an optical depth of 9:8 m 5. The spectral slopes can be used to discriminate between starburst and AGN powered sources. The monochromatic continuum fluxes at 15 and 30 m enable a remarkably accurate estimate of the total infrared luminosity of the starburst. We find that the PAH equivalent width is independent of the total starburst luminosity LIR as both continuum and PAH feature scale proportionally. However, the luminosity of the 6.2 m feature scales with LIR and can be used to approximate the total infrared luminosity of the starburst. Although our starburst sample covers about a factor of 10 difference in the [Ne iii]/ [Ne ii] ratio, we found no systematic correlation between the radiation field hardness and the PAH equivalent width or the 7.7 m/11.3 m PAH ratio. These results are based on spatially integrated diagnostics over an entire starburst region, and local variations may be ‘‘averaged out.’’ It is presumably due to this effect that unresolved starburst nuclei with significantly different global properties appear spectrally as rather similar members of one class of objects. 
  • Galaxies,
  • Starburst,
  • Infrared
Publication Date
December 20, 2006
Publisher Statement
This version of the paper was obtained from In order for the work to be deposited in, the author must have copyright or it must be available under the Creative Commons Attribution license,Creative Commons Attribution-Noncommercial-ShareAlike license, orCreate Commons Public Domain Declaration. The publisher's final edited version of this article will be available at The Astrophysical Journal.
Citation Information
Sarah J.U. Higdon, B. R. Brandl, J. Bernard-Salas, H. W. W. Spoon, et al.. "The Mid-Infrared Properties of Starburst Galaxies from Spitzer-IRS Spectroscopy" The Astrophysical Journal Vol. 653 Iss. 2 (2006) p. 1129 - 1144
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