Physics Department

Astrophysics Seminar
New observational constraints on theories of galaxy accretion and feedback
Jonathan Stern
MPIA, Heidelberg
28/05/2017, 14:30 - 15:30
Lidow, 620


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 inflows from the intergalactic medium, which provide fuel for star formation in the galaxy. I will demonstrate that the physical properties of inflows can be constrained from spectra and photometry of background quasars which sightlines pass within ~1 Mpc of galaxies. I will then present the implied properties of inflows around low-redshift ~L* galaxies, as derived from recent HST-COS and SDSS observations. Our analysis suggests that inflows around blue galaxies are significantly different from inflows around red galaxies.

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