Description
Optically luminous early type galaxies inhabit dense environments and host X-ray luminous, hot atmospheres. At fainter optical magnitudes, as the dark matter halos decrease in mass, the energy input into the hot atmospheres is likely able to drive galactic winds and expel much of the hot gas that accumulates from stellar mass loss or remains from earlier epochs of galaxy formation. In addition, there are a very few examples of galaxies which are unusually X-ray luminous with large dark matter halo masses and large SMBHs but have small optical luminosities (i.e., NGC4342 and NGC4291). These properties suggest that, in some galaxies, star formation can be truncated at early times, breaking the simple scaling relations. Current X-ray galaxy samples are very biased toward more massive (more luminous) systems. eRosita will provide an unprecedented view of the early type galaxy population. In addition, eRosita will enable "stacking" of all subtypes of early type galaxies to probe to fainter optical luminosities (and hence halo masses; assuming a correlation between stellar mass and halo mass, for most galaxies). We will discuss the current state of early type galaxy samples and eRosita's impact for understanding the atmospheres of early-type galaxies, feedback from SMBHs, and the formation of the stellar mass component of early type galaxies at the time of star formation.
