The Interstellar and Circumgalactic Media at low and high redshift as traced by Atomic Carbon and Carbon Monoxide

A different chemistry of the interstellar medium (ISM) is expected in the circumgalactic medium (CGM) gas where high-energetic particles (i.e. cosmic rays) seem to be produced in-situ by the hot X-ray gas, as it is observed in the Perseus cluster. This very different astrochemistry, where extreme gas-dust thermal decoupling is expected, and where CO can be destroyed over large massscales, is the subject of the investigation briefly reported here. We introduce an on-going project aiming at studying the properties of the CGM of two clusters at low and high redshift using their molecular gas tracers and thermal emission from dust.