[Phys-seminars] 2017-04-05 Astrophysics and Cosmology Seminar

griv griv at bgu.ac.il
Sun Apr 2 09:25:29 IDT 2017

Astrophysics and Cosmology Seminar

 DATE: 05-04-17

 TIME: 11:15

 PLACE: Seminar Room 207, Building 54

New observational constraints on theories of galaxy accretion and feedback

Dr. Jonathan Stern, Northwestern University

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 the physical properties of the circumgalactic medium (CGM), which regulate the accretion rate onto the galaxy. I will present a new technique to constrain the CGM thermal properties and chemical abundance, based on the signatures impri
 nted by the CGM on the spectra and photometry of background sources. I will demonstrate that recent HST-COS and SDSS observations suggest that the CGM is highly metal-enriched, and that its thermal state is strongly coupled to the galaxy star formation rate. This result provides a challenge for cosmological hydro-simulations.

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