12:00–1:00 pm Zoom
Host: Vikram Dwarkadas
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Congyao Zhang "Giant Shock Waves in Galaxy Clusters"
Hot gas (a.k.a., intracluster medium, ICM) is an important matter component of galaxy clusters, confined within the gravitational potential of the dark matter (DM) halos. Its detection, especially in the cluster outskirts, is one of the major goals of the next-generation X-ray and sub-mm/SZ telescopes. An interesting observational feature of the ICM is its shock structures, which are driven by feedback, mergers, and accretion. In this talk, I will discuss the formation and evolution of giant shocks on Mpc scales in the outskirts of galaxy clusters. I will introduce the concept of runaway merger shocks, which are considered as promising candidates for powering radio relics in the periphery of galaxy clusters. The Coma cluster shows a beautiful example of these runaway shocks. They eventually overtake the accretion shock at the boundary of the ICM and re-shape the gas atmospheres in the outer cluster regions. This picture naturally explains the prominent radial offset between the boundaries of gas and DM halos in galaxy clusters, long noticed in the cosmological simulations.
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Insung Jang "Stellar outskirts of NGC 300: an exceptionally extended disk or an abnormally massive halo?"
The very outer parts of galaxies are believed to still contain latent information that could reveal the early formation history of galaxies. Observations have shown that massive disk galaxies do have stellar halos and their halo properties are diverse in terms of mass, mass fraction and metallicity. For low-mass disk galaxies, however, our knowledge is still limited, mainly due to the even fainter stellar structures around the galaxies. NGC 300 is a low-mass disk galaxy in the Sculptor group. In this talk, I present my on-going work to quantify the disk and halo properties of NGC 300 based on resolved stars.
