Colloquia Schedule

Elizabeth Blanton (Boston University)

March 5, 2015, 3:45 p.m. — LGRT 1033
Title: Extragalactic Jets as Probes of Clusters of Galaxies

Abstract: I will present multi-wavelength (X-ray, optical, infrared, and radio) observations of clusters of galaxies, including in-depth study of nearby objects and a survey of distant systems. Cooling of the hot intracluster medium in cluster centers can feed the supermassive black holes in the cores of the dominant cluster galaxies leading to AGN outbursts. This AGN feedback can reheat the gas, stopping cooling and large amounts of star formation. Most relaxed, cool core clusters host powerful AGN in their central galaxies and these AGN can significantly affect the distribution of e.g., temperature and abundance on cluster scales. AGN heating can come in the form of shocks, buoyantly rising bubbles that have been inflated by radio jets and lobes, and sound wave propogation. Sloshing of the cluster gas, related to minor, off-center interactions with galaxy sub-clusters or groups also affects the distribution of temperature and abundance on large scales. This sloshing gas can interact with the AGN's radio-emitting jets and lobes causing them to bend. This bending is also found in AGN jets and lobes embedded in clusters undergoing major, head-on cluster, cluster mergers. Since this bending is a signature of interaction within clusters, bent, double-lobed AGN observed in the radio can be used as beacons for clusters of galaxies at high redshifts. I will describe our large sample of high-redshift, bent-double radio sources that were observed in the infrared with Spitzer and that have yielded approximately 200 new, distant clusters of galaxies with z > 0.7. These clusters will serve as important laboratories for studying galaxy evolution and cosmology.

Beth Willman (Haverford)

March 12, 2015, 3:45 p.m. — LGRT 1033
Title: TBA

Rob Simcoe (MIT)

March 26, 2015, 3:45 p.m. — LGRT 1033
Title: TBA

Katja Poppenhaeger (CfA)

April 2, 2015, 3:45 p.m. — LGRT 1033
Title: A high-energy view of exoplanets and their host stars

Abstract: Many exoplanets orbit their host stars at close distances, with orbital periods of only a few days. For such systems, the magnetic activity of the planet-hosting star determines the high-energy environment of its exoplanet and is an important factor in understanding the exoplanetary evolution. X-ray and UV observations allow us to determine the high-energy input into the exoplanetary atmosphere, which is the main driver of planetary evaporation. X-ray emission is also directly connected to the stellar rotation; without external input of angular momentum, the star spins down over time due to magnetic braking. However, if there is tidal interaction between a star and its Hot Jupiter, the spin-down of the host star may not follow the usual age/rotation/activity relations. I will discuss recent X-ray and UV observations which provide insights into both the evaporation of close-in exoplanets and a possibly altered age-activity relationship for host stars of such planets.

Pieter van Dokkum (Yale University)

April 9, 2015, 3:45 p.m. — LGRT 1033
Title: A history of the dense cores of massive galaxies

Tracy Webb (McGill University)

April 16, 2015, 3:45 p.m. — LGRT 1033
Title: TBA

Meredith Hughes (TBA)

April 23, 2015, 3:45 p.m. — LGRT 1033
Title: TBA