Radiation pressure from massive star clusters as a launching mechanism for super-galactic winds - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate




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Abstract: Galactic outflows of low ionization, cool gas are ubiquitous in localstarburst galaxies, and in the majority of galaxies at high redshift. How thesecool outflows arise is still in question. Hot gas from supernovae has long beensuspected as the primary driver, but this mechanism suffers from its tendencyto destroy the cool gas as the latter is accelerated. We propose a modificationof the supernova scenario that overcomes this difficulty.Star formation is observed to take place in clusters; in a given galaxy, thebulk of the star formation is found in the ~20 most massive clusters. We showthat, for L* galaxies, the radiation pressure from clusters with M>10^6 M sunis able to expel the surrounding gas at velocities in excess of the circularvelocity of the disk galaxy. This cool gas can travel above the galactic diskin less than 2 Myr, well before any supernovae erupt in the driving cluster.Once above the disk, the cool outflowing gas is exposed to radiation, andsupernovae induced hot gas outflows, from other clusters in the disk, whichdrive it to distances of several tens to hundreds of kpc. Because theradiatively driven clouds grow in size as they travel, and because the hot gasis more dilute at large distance, the clouds are less subject to destruction ifthey do eventually encounter hot gas. Therefore, unlike wind driven clouds,radiatively driven clouds can survive to distances ~50 kpc. We identify thesecluster-driven winds with large-scale galactic outflows. Another implication ofour model is that only starburst galaxies, where massive clusters reside, areable to drive winds cold outflows on galactic scales via this mechanism. Wefind that the critical star formation rates above which large scale cooloutflows will be launched to be ~0.1 M sun-yr-kpc^2, which is in good agreementwith observations.



Author: Norman Murray, Brice Ménard, Todd A. Thompson

Source: https://arxiv.org/







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