A CONSTANT MOLECULAR GAS DEPLETION TIME IN NEARBY DISK GALAXIES
- Department of Astronomy, Radio Astronomy Laboratory, University of California, Berkeley, CA 94720 (United States)
- National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
- Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, 69117 Heidelberg (Germany)
- Centre for Astrophysics Research, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom)
- IRAM, Avenida Divina Pastora 7, E-18012 Granada (Spain)
- IRAM, 300 rue de la Piscine, 38406 St. Martin d'Heres (France)
- Observatorio Astronomico Nacional, C/Alfonso XII, 3, 28014 Madrid (Spain)
We combine new sensitive, wide-field CO data from the HERACLES survey with ultraviolet and infrared data from GALEX and Spitzer to compare the surface densities of H{sub 2}, {Sigma}{sub H2}, and the recent star formation rate, {Sigma}{sub SFR}, over many thousands of positions in 30 nearby disk galaxies. We more than quadruple the size of the galaxy sample compared to previous work and include targets with a wide range of galaxy properties. Even though the disk galaxies in this study span a wide range of properties, we find a strong, and approximately linear correlation between {Sigma}{sub SFR} and {Sigma}{sub H2} at our common resolution of 1 kpc. This implies a roughly constant median H{sub 2} consumption time, {tau}{sup H2}{sub Dep} = {Sigma}{sub H2}/{Sigma}{sub SFR}, of {approx}2.35 Gyr (including heavy elements) across our sample. At 1 kpc resolution, there is only a weak correlation between {Sigma}{sub H2} and {tau}{sup H2}{sub Dep} over the range {Sigma}{sub H2} {approx} 5-100 M{sub sun} pc{sup -2}, which is probed by our data. We compile a broad set of literature measurements that have been obtained using a variety of star formation tracers, sampling schemes, and physical scales and show that overall, these data yield almost exactly the same results, although with more scatter. We interpret these results as strong, albeit indirect evidence that star formation proceeds in a uniform way in giant molecular clouds in the disks of spiral galaxies.
- OSTI ID:
- 21560429
- Journal Information:
- Astrophysical Journal Letters, Vol. 730, Issue 2; Other Information: DOI: 10.1088/2041-8205/730/2/L13; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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