Astronomy & Astrophysics Seminar: New observational constraints on theories of galaxy accretion and feedback

Abstract:

I will present two novel observational tests of astrophysical theories that are central to our understanding of galaxy evolution.

The first test concerns quasar-driven galactic-scale outflows, which are often invoked by cosmological simulations to regulate star formation in massive galaxies. Several physical mechanisms have been proposed for the acceleration of these outflows, such as the ram pressure of shock-heated nuclear winds and radiation pressure on dust grains. I will demonstrate that the nature of the acceleration mechanism can be constrained using emission lines that originate from HII regions surrounding quasars. I will then present new constraints derived from observations with Gemini, Chandra, HST and SDSS.

The second test concerns gas in the dark matter halos of galaxies, which is a source of fuel for star formation in the galaxy. Cosmological simulations typically predict that around low-redshift ~L* galaxies, the halo gas is predominantly `hot', roughly at the virial temperature of the halo. I will present some challenges posed to this picture by recent observations with HST and SDSS, and suggest an alternative physical model which can explain the observations.

Seminar Organizer: Prof. Sara Beck