Lecturer: Dr. Jonathan Stern Affiliation: Galaxies and Cosmology Department Max-Planck-Institute for Astronomy [MPIA] 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 the circumgalactic medium (CGM), which is the reservoir of fuel for future star formation in the galaxy. I will demonstrate that the CGM thermal properties, which regulate the accretion rate onto the galaxy, can be constrained from absorption features imprinted by highly ionized oxygen and neutral hydrogen on the ultraviolet spectra of background sources. I will show that recent HST-COS observations of these features suggest that the thermal state of the CGM is strongly coupled to the galaxy star formation rate, and that this result provides a challenge for modern hydro- simulations. Additional details of the upcoming Astrophysics' seminars can be found on the following link. ‏האירוע הזה כולל שיחת וידאו ב-Google Hangouts. הצטרף: https://plus.google.com/hangouts/_/mail.huji.ac.il/astrophysics?hceid=bWFpbC5odWppLmFjLmlsX2c0czhydDlpcmhwZzRvdGNybWIzZGFqcjdvQGdyb3VwLmNhbGVuZGFyLmdvb2dsZS5jb20.3v60444msrjk7okit3bmjmgmck&hs=121