Abstract: Despite its fundamental role in shaping galaxy evolution, the interplay between star formation, galactic feedback, and gas accretion remains poorly understood in both observations and theory. In this talk, I will discuss how the circumgalactic medium (CGM)—a multiphase gas reservoir surrounding galaxies—serves as a powerful diagnostic to resolve these processes, probed in multi-wavelength observations, including UV absorption, optical IFU, radio HI 21 cm, and X-ray. I will introduce the general picture of the multiphase CGM, and focus on the recent progress in mapping the spatial distribution and kinematics of the diffuse gas. The spatial distribution of the CGM exhibits a significant correlation with the star formation rates of host galaxies, as a result of concentrated gas assembly or stellar-driven feedback. Encoded in the high-quality spectra, the velocity field in the CGM exhibits both global flows and strong turbulent motions. In particular, the enhanced turbulence around QSO host galaxies indicates large-scale, powerful feedback from supermassive black holes. Future synthesis of multiwavelength data will provide new insights into the CGM’s role in regulating galaxy growth.
Bio: Zhijie Qu is an Assistant Professor at Tsinghua University, before which he was a postdoctoral scholar at the University of Chicago. He received his PhD from the University of Michigan and his bachelor's degree from Peking University. His research specializes in characterizing multiphase diffuse gas using multi-wavelength observational techniques, including UV/optical absorption surveys, integral-field spectrographs, radio HI 21cm, X-ray observations, and the Sunyaev-Zeldovich effect, to elucidate the fundamental baryonic cycle in galaxy evolution.