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A Census of Galactic Winds in the Local Universe

Ed Elson
International Centre for Radio Astronomy Research

The mechanical energy deposited by high-mass star formation and supernova explosions into the interstellar medium is capable of expelling a galaxy's gas into its halo, resulting in various neutral and ionized gas structures. Given that such feedback processes dominate the chemical enrichment of the intergalactic medium, detecting and studying them at multiple wavelengths in nearby galaxies provides us with the opportunity to better understand one of the dominant processes of galaxy evolution.
Using R-band continuum and narrow-band H-alpha imaging from the Survey for Ionization in Neutral Gas Galaxies, we have identified ~ 100 out of 200 moderately- to highly-inclined star-forming galaxies as having ionized hydrogen in their halos. We show, statistically, that the extra-planar H-alpha is more extended along the minor axis, in quantitative agreement with the theory of galaxy winds. Using our optically unbiased sample of galaxies we study the wind properties over a wide range of star formation rates with the aim of identifying the physical conditions required for mass ejection. We quantify the incidence rate of wind activity as a function of HI mass, R-band luminosity and star formation rate. Ultimately, our aim is to determine the metallicity ejection rate and hence the rate of metal pollution of the intergalactic medium.

2012 July 19, 13:30

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