TRACING COLD H I GAS IN NEARBY, LOW-MASS GALAXIES
- Minnesota Institute for Astrophysics, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States)
- Department of Astronomy, Box 351580, University of Washington, Seattle, WA 98195 (United States)
- National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
- Max Planck Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)
- Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, IL 61801 (United States)
- Australia Telescope National Facility, CSIRO Astronomy and Space Science, P.O. Box 76, Epping NSW 1710 (Australia)
We analyze line-of-sight atomic hydrogen (H I) line profiles of 31 nearby, low-mass galaxies selected from the Very Large Array-ACS Nearby Galaxy Survey Treasury (VLA-ANGST) and The H I Nearby Galaxy Survey (THINGS) to trace regions containing cold (T {approx}< 1400 K) H I from observations with a uniform linear scale of 200 pc beam{sup -1}. Our galaxy sample spans four orders of magnitude in total H I mass and nine magnitudes in M{sub B} . We fit single and multiple component functions to each spectrum to isolate the cold, neutral medium given by a low-dispersion (<6 km s{sup -1}) component of the spectrum. Most H I spectra are adequately fit by a single Gaussian with a dispersion of 8-12 km s{sup -1}. Cold H I is found in 23 of 27 ({approx}85%) galaxies after a reduction of the sample size due to quality-control cuts. The cold H I contributes {approx}20% of the total line-of-sight flux when found with warm H I. Spectra best fit by a single Gaussian, but dominated by cold H I emission (i.e., have velocity dispersions of <6 km s{sup -1}), are found primarily beyond the optical radius of the host galaxy. The cold H I is typically found in localized regions and is generally not coincident with the very highest surface density peaks of the global H I distribution (which are usually areas of recent star formation). We find a lower limit for the mass fraction of cold-to-total H I gas of only a few percent in each galaxy.
- OSTI ID:
- 22092228
- Journal Information:
- Astrophysical Journal, Vol. 757, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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