Probing the effects of SMBH feedback on the CGM with Line Emission Mapper (LEM) mission

The circumgalactic medium (CGM) plays an essential role in the formation and evolution of galaxies. It is the interface where inflows from cosmic gas and outflows driven by galactic feedback meet. At the same time, supermassive black holes (SMBH) are thought to be the central engines powering feedback driving large-scale outflows, injecting mass, energy and metals into the CGM. Modern simulations predict that these processes have a large impact on the physical state of the CGM including: i) Diversity between star-forming and quiescent galaxies at the Milky-Way mass range; and ii) Anisotropic distribution in the CGM thermodynamic properties and metal content. However, probing these effects is challenging, even impossible, with current X-ray CCD detectors. In this work, we carry out a forecast study on the prospects of the Line Emission Mapper (LEM) Probe Mission for probing Active Galactic Nuclei feedback effects on the CGM. LEM is a microcalorimeter-based X-ray imaging spectrometer with a large field of view (30’x30’) and unprecedented spectral resolution (1-2 eV). Based on analyzing state-of-the-art cosmological simulations of galaxies (including IllustrisTNG, EAGLE, and SIMBA), we show that the three simulations consistently predict a dichotomy between star-forming and quiescent galaxies in X-ray emission metal lines, which is a direct manifestation of the SMBH feedback-driven quenching mechanism. In addition, these simulations also predict that SMBH feedback drives the CGM anisotropy traced by line emission, though the anisotropic signal is quantitatively different among the simulations. Finally we show that LEM will be capable of mapping CGM emission (in prominent lines such as OVII, OVIII, and FeXVII) out to a significant fraction of the virial radius (R200) in a representative sample of galaxies, whereby enabling us to probe those predicted SMBH feedback imprints on the CGM.