Arendt, R. G. and Stolovy, S. R. and Ramirez, S. V. and Sellgren, K. and Cotera, A. S. and Law, C. J. and Yusef-Zadeh, F. and Smith, H. A. and Gezari, D. Y. (2008) The mid-infrared colors of the interstellar medium and extended sources at the Galactic center. Astrophysical Journal, 682 (1). pp. 384-399. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:AREapj08
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A mid-infrared (3.6–8 μm) survey of the Galactic center has been carried out with the IRAC instrument on the Spitzer Space Telescope. This survey covers the central 2º x 1.4º (~280 x 200 pc) of the Galaxy. At 3.6 and 4.5 μm the emission is dominated by stellar sources, the fainter ones merging into an unresolved background. At 5.8 and 8 μm the stellar sources are fainter, and large-scale diffuse emission from the ISM of the Galaxy's central molecular zone becomes prominent. The survey reveals that the 8-to-5.8 μm color of the ISM emission is highly uniform across the surveyed region. This uniform color is consistent with a flat extinction law and emission from polycyclic aromatic hydrocarbons (PAHs). Models indicate that this broadband color should not be expected to change if the incident radiation field heating the dust and PAHs is <10^4 times that of the solar neighborhood. The few regions with unusually red emission are areas where the PAHs are underabundant and the radiation field is locally strong enough to heat large dust grains to produce significant 8 μm emission. These red regions include compact H II regions, Sgr B1, and wider regions around the Arches and Quintuplet clusters. In these regions the radiation field is >~10^4 times that of the solar neighborhood. Other regions of very red emission indicate cases where thick dust clouds obscure deeply embedded objects or very early stages of star formation.
|Additional Information:||© 2008. The American Astronomical Society. Received 2007 October 4; accepted 2008 April 23. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. This research hasmade use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. We thank the referee for pointing out the nonnegligible influence of the 4.5 µm ISM emission in our analysis. Facilities: Spitzer ( IRAC)|
|Subject Keywords:||dust, extinction—Galaxy: center—infrared: ISM|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Marie Noren|
|Deposited On:||09 Oct 2008 16:57|
|Last Modified:||26 Dec 2012 10:22|
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