Radiation Pressure from Massive Star Clusters as a Launching Mechanism for Super-galactic Winds

• Published in: The Astrophysical journal Vol. 735; no. 1; pp. 66 - jQuery1323907166958='48'
• Main Authors: Murray, Norman, Ménard, Brice, Thompson, Todd A
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.07.2011; IOP
• Subjects: Astronomy; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BINARY STARS; CLOUDS; COSMIC GASES; DENSITY; Earth, ocean, space; ERUPTIVE VARIABLE STARS; Exact sciences and technology; FLUIDS; GALAXIES; GASES; MASS; PHYSICAL PROPERTIES; RADIATION PRESSURE; STAR CLUSTERS; STARS; STELLAR ACTIVITY; STELLAR WINDS; SUPERNOVAE; VARIABLE STARS; Quasars; Intergalactic matter; Red shift; Galactic wind; Starburst galaxies; quasars: absorption lines; Disk galaxies; intergalactic medium; Star clusters; Galactic disks; Formation rate; Radiation pressure; ISM: structure; Massive stars; Galaxy clusters; Absorption line; extinction; Star formation; Galactic supernova; Hot gas; dust; galaxies: star clusters: general
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/735/1/66

Galactic outflows of cool (~104 K) gas are ubiquitous in local starburst galaxies and in most high-redshift galaxies. Hot gas from supernovae has long been suspected as the primary driver, but this mechanism suffers from its tendency to destroy the cool gas. We propose a modification of the supernova scenario that overcomes this difficulty. Star formation is observed to take place in clusters. We show that, for L galaxies, the radiation pressure from clusters with M cl 106 M is able to expel the surrounding gas at velocities in excess of the circular velocity vc of the disk galaxy. This cool gas travels above the galactic disk before supernovae erupt in the driving cluster. Once above the disk, the cool outflowing gas is exposed to radiation and hot gas outflows from the galactic disk, which in combination drive it to distances of ~50 kpc. Because the radiatively driven clouds grow in size as they travel, and because the hot gas is more dilute at large distance, the clouds are less subject to destruction. Therefore, unlike wind-driven clouds, radiatively driven clouds can give rise to the metal absorbers seen in quasar spectra. We identify these cluster-driven winds with large-scale galactic outflows. The maximum cluster mass in a galaxy is an increasing function of the galaxy's gas surface density, so only starburst galaxies are able to drive cold outflows. We find the critical star formation rate for launching large-scale cool outflows to be , in good agreement with observations.