  Interstellar (ISM) and circumgalactic mediums (CGM) around galaxies are
linked to several physical processes that drive galaxy evolution. For example,
the X-ray emission from the CGM gas around ellipticals has been linked to the
AGN feedback occurring in the host. Upcoming telescopes, such as HUBS with ~2
eV resolution, can provide us with deep insights about the hot gas properties
of such galaxies thus constrain these processes. In this project, we discuss
X-ray emission of the ISM and CGM of elliptical galaxies simulated using MACER
code. We generate X-ray emission data from the MACER simulations with various
feedback models and produce mock observations for an instrument with high
spectral resolution, which is a necessary step of selecting sources for the
future observations with planned mission such as HUBS. More importantly, we
establish connections between the physics of AGN and stellar feedback with the
emission spectra from the ISM and CGM to investigate the possibility of using
observations to constrain feedback models. We fit the X-ray spectra from these
simulations with standard fitting procedures and compare the retrieved physical
properties with their counterparts from the simulations to understand whether
the future high-resolution observations can reliably reveal the properties of
the gas in the galaxies.
