1. The Mid‐Infrared Properties of Starburst Galaxies fromSpitzer‐IRS Spectroscopy
- Author
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Brandl, B. R., Bernard-Salas, J., Spoon, Henrik W. W., Devost, Daniel, Sloan, G. C., Guilles, S., Wu, Y., Houck, J. R., Weedman, Dan W., Armus, Lee, Appleton, Philip N., Soifer, B. T., Charmandaris, Vassilis, Hao, Lei, Higdon, J. A., Marshall, S. J., Herter, T. L., Leiden University, Department of Astronomy, Cornell University, Spitzer Fellow, Spitzer Science Center, California Institute of Technology (SSC), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS), and Crete Center for Theoretical Physics, Department of Physics
- Subjects
Physics ,Infrared ,Astronomy and Astrophysics ,Starburst region ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Galaxy ,Spectral line ,Star cluster ,Spitzer Space Telescope ,Space and Planetary Science ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Spectral resolution ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,Equivalent width ,Astrophysics::Galaxy Astrophysics - Abstract
We present 5 38µm mid-infrared spectra at a spectral resolution of R � 65 130 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 in starburst SEDs. The silicate absorption ranges from essentially no absorption to heavily obscured systems with an optical depth of �9.8µm � 5. The spectral slopes can be used to discriminate between starburst and AGN powered sources. The monochromatic continuum fluxes at 15µm and 30µm 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 6.2µm 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 ten difference in the [NeIII]/[NeII] ratio, we found no systematic correlation between the radiation field hardness and the PAH equivalent width or the 7.7µm/11.3µm 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. Subject headings: Telescopes: Spitzer, Galaxies: ISM, starburst, star clusters ISM: dust, extinction, HII regions
- Published
- 2006
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