Two Talks: Linking The Most Massive Galaxies To Their Hot Gas Halos (speaker: Andy Goulding, Princeton); Escape Fraction Of Ionizing Photons – The Impact Of Binary Stars (speaker: Xiangcheng Ma, CalTech)

Monday May 9, 2016 12:05 pm
Marlar Lounge (37-252)

Talk #1 — Linking the most massive galaxies to their hot gas halos

Speaker: Andy Goulding, Princeton

Abstract:  Studies of the physical properties of local elliptical galaxies (e.g., gas temperatures, halo masses, stellar kinematics) are shedding new light on galaxy formation. I will present our recent investigations into the X-ray and optical properties of nearby, massive early-type galaxies. We harness the exquisite spatial resolution and sensitivity of the Chandra X-ray observatory, combined with integral field optical spectroscopy, to provide the most complete picture to date, of the influence of large and small scale environment on the evolution of elliptical galaxies.

Host: Esra Bulbul

Talk #2 — Escape fraction of ionizing photons – the impact of binary stars

Speaker: Xiangcheng Ma, Caltech

Abstract: The escape fraction of Lyman Continuum photons needs to be ~20% in order to ionize the universe. We use the high-resolution cosmological zoom-in simulations from the FIRE project, which include detailed models of the multi-phase ISM, star formation, and stellar feedback, and Monte Carlo radiative transfer code, to study the escape fraction from dwarf galaxies at z>6. Using ‘standard’ stellar population models from STARBURST99, we find that the time-averaged escape fraction is ~5%, far below the requirement of reionization. This is because most of the absorption comes from individual star-forming clouds, while the timescale for stellar feedback to destroy these birth clouds is comparable to the lifetime of massive stars that produce most of the ionizing photons. However, stellar population models that include binary interaction (e.g. the BPASS model) predict much more ionizing photons than single-star models from STARBURST99 at late times. We find that using BPASS model, the predicted escape fraction can be boosted by a factor of 4-10, which matches the requirement of deionization.

Host: Paul Torrey