LAUSR

We create mock X-ray observations of hot gas in galaxy clusters with a new extension of L-Galaxies semi-analytic model of galaxy formation, which includes the radial distribution of hot gas in each halo. Based on the model outputs, we first build some mock light cones, then generate mock spectra with SOXS package and derive the mock images in the light cones. Using the mock data, we simulate the mock X-ray spectra for \emph{ROSAT} all-sky survey, and compare the mock spectra with the observational results. Then, we consider the design parameters of \emph{HUBS} mission and simulate the observation of the halo hot gas for \emph{HUBS} as an important application of our mock work. We find: (1) Our mock data match the observations by current X-ray telescopes. (2) The survey of hot baryons in resolved clusters by \emph{HUBS} is effective below redshift 0.5, and the observations of the emission lines in point-like sources at $z>0.5$ by \emph{HUBS} help us understand the hot baryons in the early universe. (3) By taking the advantage of the large simulation box and flexibility in semi-analytic models, our mock X-ray observations provide the opportunity to make target selection and observation strategies for forthcoming X-ray facilities.