THE DISRUPTION OF GIANT MOLECULAR CLOUDS BY RADIATION PRESSURE and THE EFFICIENCY OF STAR FORMATION IN GALAXIES
- Canadian Institute for Theoretical Astrophysics, 60 St. George Street, University of Toronto, Toronto, ON M5S 3H8 (Canada)
- Astronomy Department and Theoretical Astrophysics Center, 601 Campbell Hall, University of California, Berkeley, CA 94720 (United States)
Star formation is slow in the sense that the gas consumption time is much longer than the dynamical time. It is also inefficient; star formation in local galaxies takes place in giant molecular clouds (GMCs), but the fraction of a GMC converted to stars is very small, epsilon{sub GMC} approx 5%. In luminous starbursts, the GMC lifetime is shorter than the main-sequence lifetime of even the most massive stars, so that supernovae can play no role in GMC disruption. We investigate the disruption of GMCs across a wide range of galaxies from normal spirals to the densest starbursts; we take into account the effects of H II gas pressure, shocked stellar winds, protostellar jets, and radiation pressure produced by the absorption and scattering of starlight on dust grains. In the Milky Way, a combination of three mechanisms-jets, H II gas pressure, and radiation pressure-disrupts the clouds. In more rapidly star-forming galaxies such as 'clump' galaxies at high-redshift, ultra-luminous infrared galaxies (ULIRGs), and submillimeter galaxies, radiation pressure dominates natal cloud disruption. We predict the presence of approx10-20 clusters with masses approx10{sup 7} M{sub sun} in local ULIRGs such as Arp 220 and a similar number of clusters with M{sub *} approx 10{sup 8} M{sub sun} in high redshift clump galaxies; submillimeter galaxies will have even more massive clusters. We find that epsilon{sub GMC} = piGSIGMA{sub GMC} c/(2(L/M{sub *})) for GMCs that are optically thin to far-infrared radiation, where SIGMA{sub GMC} is the GMC gas surface density. The efficiency in optically thick systems continues to increase with SIGMA{sub GMC}, but more slowly, reaching approx35% in the most luminous starbursts. The disruption of bubbles by radiation pressure stirs the interstellar medium (ISM) to velocities of approx10 km s{sup -1} in normal galaxies and to approx100 km s{sup -1} in ULIRGs like Arp 220, consistent with observations. Thus, radiation pressure may play a dominant dynamical role in the ISM of star-forming galaxies.
- OSTI ID:
- 21392354
- Journal Information:
- Astrophysical Journal, Vol. 709, Issue 1; Other Information: DOI: 10.1088/0004-637X/709/1/191; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COSMOLOGY AND ASTRONOMY
ABSORPTION
DUSTS
FAR INFRARED RADIATION
MASS
MILKY WAY
RADIATION PRESSURE
RED SHIFT
SCATTERING
STAR CLUSTERS
STELLAR WINDS
SUPERNOVAE
BINARY STARS
ELECTROMAGNETIC RADIATION
ERUPTIVE VARIABLE STARS
GALAXIES
INFRARED RADIATION
RADIATIONS
SORPTION
STARS
STELLAR ACTIVITY
VARIABLE STARS