Galactic winds in star forming galaxies and AGNs: is there evidence for AGN feedback

Galactic-scale gas flows are one of the most fundamental, yet least understood, facets of galaxy evolution. They are fundamental in shaping the build-up of galaxies and their morphologies, in regulating star formation and metallicity of galaxies as well as the enrichment of the circum-galactic medium. I will give an overview of the relatively young field of galactic winds and discuss recent progresses. I will present several observational results and show that there is convincing evidence that galactic winds are common. We observe blue shifts or broad line profiles from multiphase outflows in star forming galaxies and AGNs in both nearby and distant galaxies. Despite laudable progress in observations in the past decade, the detail physical properties of the wind (such as geometry and extent of the wind, the mass outflow rate, driving mechanism, kinetic coupling efficiencies, etc) are very uncertain or yet unknown. The impact of AGN outflows (e.g, on star-formation quenching) is also not clear. Most absorption line studies of the cool gas indicate moderate average wind velocities (~200 km/s) in AGNs, which are similar to those in star-forming and  starburst galaxies. However, the wind velocity dispersions (or maximum velocities) of the ionized gas are likely higher in AGNs by about a factor of two; Some of the gas in AGN reaches ~1000-2000 km/s. It is not clear if this high velocity gas is a significant fraction of the total mass or if it is most of the gas.

Discussion Leader: 
Hassen Yesuf
Thursday, November 22, 2018 - 12:00pm to 1:00pm