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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 308817.0, MPI für Astronomie / Publikationen_mpia
The nature of infrared emission in the Local Group dwarf galaxy NGC 6822 as revealed by Spitzer
Authors:Cannon, J. M.; Walter, F.; Armus, L.; Bendo, G. J.; Calzetti, D.; Draine, B. T.; Engelbracht, C. W.; Helou, G.; Kennicutt, R. C.; Leitherer, C.; Roussel, H.; Bot, C.; Buckalew, B. A.; Dale, D. A.; de Blok, W. J. G.; Gordon, K. D.; Hollenbach, D. J.; Jarrett, T. H.; Meyer, M. J.; Murphy, E. J.; Sheth, K.; Thornley, M. D.
Date of Publication (YYYY-MM-DD):2006
Journal Abbrev.:The Astrophysical Journal
Start Page:1170
End Page:1187
Audience:Not Specified
Abstract / Description:We present Spitzer imaging of the metal-deficient (Z~=30% Zsolar) Local Group dwarf galaxy NGC 6822. On spatial scales of ~130 pc, we study the nature of IR, Halpha, H I, and radio continuum emission. Nebular emission strength correlates with IR surface brightness; however, roughly half of the IR emission is associated with diffuse regions not luminous at Halpha (as found in previous studies). The global ratio of dust to H I gas in the ISM, while uncertain at the factor of ~2 level, is ~25 times lower than the global values derived for spiral galaxies using similar modeling techniques; localized ratios of dust to H I gas are about a factor of 5 higher than the global value in NGC 6822. There are strong variations (factors of ~10) in the relative ratios of Halpha and IR flux throughout the central disk; the low dust content of NGC 6822 is likely responsible for the different Halpha/IR ratios compared to those found in more metal-rich environments. The Halpha and IR emission is associated with high column density (>~1021 cm-2) neutral gas. Increases in IR surface brightness appear to be affected by both increased radiation field strength and increased local gas density. Individual regions and the galaxy as a whole fall within the observed scatter of recent high-resolution studies of the radio-far-IR correlation in nearby spiral galaxies; this is likely the result of depleted radio and far-IR emission strengths in the ISM of this dwarf galaxy.
Free Keywords:Galaxies: Dwarf; Galaxies: Individual: NGC Number: NGC 6822; Galaxies: Irregular; Galaxies: ISM; Infrared: Galaxies
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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