Galactic Superwinds at Low and High Redshift

Abstract

In this contribution I summarize our current knowledge of the nature and significance of starburst-driven galactic superwinds. These flows are driven primarily by the kinetic energy supplied by supernovae. Superwinds are complex, multiphase phenomena requiring a panchromatic observational approach. They are ubiquitous in galaxies in which the global star-formation rate per unit area exceeds roughly 10$^{-1}$ M$_{\odot}$ yr$^{-1}$ kpc$^{-2}$ (a condition satisfied by local starbursts and high-z Lyman Break galaxies). Data on X-ray emission, optical line-emission, and optical/UV interstellar absorption-lines together imply that the mass outflow rates are comparable to the star-formation-rates and that the conversion of kinetic energy from supernovae to superwind is quite efficient ($\sim$ 30 to 100%). Measured/inferred outflow speeds range from a few $\times 10^2$ to 10$^3$ km/s and appear to be independent of the rotation speed of the ``host'' galaxy. The outflows are dusty (dust/gas ratios of $\sim$ 1% by mass). These properties imply that superwinds may have established the mass-metallicity relation in elliptical and bulges, polluted the inter-galactic medium to a metallicity of $\sim$ 10 to 30% solar, heated the inter-galactic medium by up to $\sim$1 kev per baryon, and ejected enough dust into the inter-galactic medium to have potentially observable consequences.