2006/08/11 by John M. Cannon, Fabian Walter, L. Armus +31 · 2 citations
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Star Formation Studies #Dwarf galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Infrared #Interacting galaxy #Irregular galaxy #Local Group #Physics #Spiral galaxy #Surface brightness #astro-ph
paper · pdf · doi:10.1086/508341
published as Astrophys.J.652:1170-1187,2006 · ApJ, in press; please retrieve full-resolution version from http://www.astro.wesleyan.edu/~cannon/pubs.html
arxiv created 2006/08/11 · openalex publication_date 2006/11/27 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present Spitzer imaging of the metal-deficient ( Z ≃ 30% Z ☉ ) Local Group dwarf galaxy NGC 6822. On spatial scales of ~130 pc, we study the nature of IR, Hα, 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 Hα (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 Hα and IR flux throughout the central disk; the low dust content of NGC 6822 is likely responsible for the different Hα/IR ratios compared to those found in more metal-rich environments. The Hα and IR emission is associated with high column density (≳10 21 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.