Small-scale properties of atomic gas in extended disks of galaxies

Sanchayeeta Borthakur, Emmanuel Momjian, Timothy M. Heckman, Donald G. York, David V. Bowen, Min S. Yun, Todd M. Tripp

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

We present high-resolution H I 21 cm observations with the Karl G. Jansky Very Large Array for three H I rich galaxies in absorption against radio quasars. Our sample contains six sightlines with impact parameters from 2.6 to 32.4 kpc. We detected a narrow H I absorber of FWHM 1.1 km s-1 at 444.5 km s-1 toward SDSS J122106.854+454852.16 probing the dwarf galaxy UCG 7408 at an impact parameter of 2.8 kpc. The absorption feature was barely resolved and its width corresponds to a maximum kinetic temperature, Tk ≈ 26 K. We estimate a limiting peak optical depth of 1.37 and a column density of 6 × 1019 cm-2. The physical extent of the absorber is 0.04 kpc2 and covers ∼25%-30% of the background source. A comparison between the emission and absorption strengths suggests the cold-to-total H I column density in the absorber is ∼30%. Folding in the covering fraction, the cold-to-total H I mass is ∼10%. This suggest that condensation of warm H I (Ts ∼ 1000 K) to cold phase (Ts < 100 K) is suppressed in UGC 7408. The unusually low temperature of the H I absorber also indicates inefficiency in condensation of atomic gas into molecular gas. The suppression in condensation is likely to be the result of low metal content in this galaxy. The same process might explain the low efficiency of star formation in dwarf galaxies despite their huge gas reservoirs. We report the non-detection of H I in absorption in five other sightlines. This indicates that either the cold gas distribution is highly patchy or the gas is much warmer (Ts > 1000 K) toward these sightlines.

Original languageEnglish (US)
Article number98
JournalAstrophysical Journal
Volume795
Issue number1
DOIs
StatePublished - Nov 1 2014
Externally publishedYes

Fingerprint

monatomic gases
absorbers
galaxies
gas
Very Large Array (VLA)
dwarf galaxies
optical thickness
folding
quasars
optical depth
condensation
coverings
radio
kinetics
high resolution
estimates
cold
temperature
parameter

Keywords

  • galaxies: dwarf
  • galaxies: ISM
  • ISM: abundances
  • ISM: structure
  • quasars: absorption lines
  • radio lines: ISM
  • ultraviolet: ISM

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Borthakur, S., Momjian, E., Heckman, T. M., York, D. G., Bowen, D. V., Yun, M. S., & Tripp, T. M. (2014). Small-scale properties of atomic gas in extended disks of galaxies. Astrophysical Journal, 795(1), [98]. https://doi.org/10.1088/0004-637X/795/1/98

Small-scale properties of atomic gas in extended disks of galaxies. / Borthakur, Sanchayeeta; Momjian, Emmanuel; Heckman, Timothy M.; York, Donald G.; Bowen, David V.; Yun, Min S.; Tripp, Todd M.

In: Astrophysical Journal, Vol. 795, No. 1, 98, 01.11.2014.

Research output: Contribution to journalArticle

Borthakur, S, Momjian, E, Heckman, TM, York, DG, Bowen, DV, Yun, MS & Tripp, TM 2014, 'Small-scale properties of atomic gas in extended disks of galaxies', Astrophysical Journal, vol. 795, no. 1, 98. https://doi.org/10.1088/0004-637X/795/1/98
Borthakur, Sanchayeeta ; Momjian, Emmanuel ; Heckman, Timothy M. ; York, Donald G. ; Bowen, David V. ; Yun, Min S. ; Tripp, Todd M. / Small-scale properties of atomic gas in extended disks of galaxies. In: Astrophysical Journal. 2014 ; Vol. 795, No. 1.
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KW - ultraviolet: ISM

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