Abstract: Extended, diffuse soft X-ray emission has been widely detected around individual galaxies and is commonly attributed to either galactic feedback processes or gravitational heating, with the latter expected to be efficient primarily in massive systems. However, in most galaxies the observed X-ray radiation efficiency—defined as the fraction of feedback energy emitted in X-rays—is far below unity, raising fundamental questions about the thermodynamic state and detectability of the hot circumgalactic medium (CGM). In this talk, I will introduce an analytical framework as a baseline model to quantify the X-ray radiation efficiency and to track the evolutionary trajectory of feedback-driven superbubbles propagating in a hot ambient medium. By comparing this baseline model with numerical simulations and X-ray observations, I will discuss its key implications for the structure, energetics, and observability of the hot CGM. I will then present observational evidence supporting the multi-phase nature of the hot CGM and discuss physical mechanisms that may help bridge the gap between theoretical expectations and observational constraints.
Bio: Jiang-Tao Li received his PhD from Nanjing University in 2010 under the supervision of Profs. Daniel Wang (University of Massachusetts Amherst) and Yang Chen (Nanjing University). He subsequently held postdoctoral positions at UMass Amherst, CEA Saclay, and the University of Michigan, Ann Arbor between 2010 and 2018. He joined the University of Michigan as research faculty in early 2018 and was promoted to Associate Research Professor in 2022. In 2023, he joined the Purple Mountain Observatory as a Full Professor. His research focuses on multi-wavelength studies of multi-phase gas across a wide range of scales, from nearby galaxies to the high-redshift universe.