Title: Gamma-ray production in the extended halo of a galaxy and its implication for the missing baryons
Speaker: 柳若愚, Nanjing University
Host: Ke Shi
Time: 14:30-16:30, Thursday, 12 Nov. 2020
Location: Physics Building 552
Abstract: Various studies suggest the existence of gaseous halos around galaxies extending out their virial radii, which are also known as the circumgalactic medium (CGM). Cosmic rays that are generated in a galaxy will eventually escape to the halo, and produce gamma-ray emissions via the hadronuclear interactions with the CGM. Different from some traditional measurements of CGM which are sensitive only to gas in certain specific temperature range, the hadronic gamma-ray flux is sensitive to baryonic gases in all phases and does not rely on the metallicity in the halo. We therefore suggest gamma-ray observation as a novel probe to the mass of the CGM. By comparing the expected gamma-ray flux with the observed one from the extended halos of Milky Way and the Andromeda Galaxy, we put a constraint on the total mass of the CGM and the baryon fraction for the two galaxies respectively. Other implications and caveats of our results will be also discussed.
Biography: I obtained my doctoral degree from the University of Heidelberg in 2015. Before I join Nanjing University, I worked as a postdoctoral researcher in Max-Planck-Institute for Nuclear Physics (MPIK) and Deutsches Electron-Synchrotron researcher center (DESY) respectively for two years. My research interest mainly focuses on (but not limited to) the astroparticle physics and the high-energy astrophysics, including the origin of high-energy cosmic rays and high-energy neutrinos, the radiation processes in dynamic astrophysical objects such blazars, gamma-ray bursts, pulsar wind nebulae, etc, as well as their roles as the accelerators of cosmic rays.