Tracing cold HI gas in nearby, low-mass galaxies

Steven R. Warren, Evan D. Skillman, Adrienne M. Stilp, Julianne J. Dalcanton, Jürgen Ott, Fabian Walter, Eric A. Petersen, Bärbel Koribalski, Andrew A. West

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

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 ≲ 1400K) H I from observations with a uniform linear scale of 200pcbeam-1. Our galaxy sample spans four orders of magnitude in total H I mass and nine magnitudes in MB . We fit single and multiple component functions to each spectrum to isolate the cold, neutral medium given by a low-dispersion (<6km s-1) component of the spectrum. Most H I spectra are adequately fit by a single Gaussian with a dispersion of 8-12kms-1. Cold H I is found in 23 of 27 (85%) galaxies after a reduction of the sample size due to quality-control cuts. The cold H I contributes 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 <6kms-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.

Original languageEnglish (US)
Article number84
JournalAstrophysical Journal
Volume757
Issue number1
DOIs
StatePublished - Sep 20 2012

Keywords

  • ISM: atoms
  • ISM: clouds
  • ISM: structure
  • galaxies: ISM
  • galaxies: dwarf
  • radio lines: ISM

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