The mid-infrared colors of the interstellar medium and extended sources at the galactic center

R. G. Arendt, S. R. Stolovy, S. V. Ramírez, K. Sellgren, A. S. Cotera, C. J. Law, F. Yusef-Zadeh, H. A. Smith, D. Y. Gezari

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


A mid-infrared (3.6Y8 μm) survey of the Galactic center has been carried out with the IRAC instrument on the Spitzer Space Telescope. This survey covers the central 2° x 1:4° (∼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 <104 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 isk104 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.

Original languageEnglish (US)
Pages (from-to)384-399
Number of pages16
JournalAstrophysical Journal
Issue number1
StatePublished - Jul 20 2008


  • Dust, extinction
  • Galaxy: center
  • Infrared: ISM

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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