Revisiting the X-ray-mass scaling relations of early-type galaxies with the mass of their globular cluster systems as a proxy for the total galaxy mass
Using globular cluster kinematics and photometry data, we calibrate the scaling relation between the total galaxy mass (MTOT, including dark matter) and total globular cluster system mass (MGCS) in a sample of 30 early-type galaxies (ETGs), confirming a nearly linear relationship between the two physical parameters. Using samples of 83 and 57 ETGs, we investigate this scaling relation in conjunction with the previously known relations between MTOT and the interstellar medium (ISM) X-ray luminosity and temperature, respectively. We confirm that MGCS can be effectively used as a proxy of MTOT. We further find that the LX,GAS-MTOT relation is far tighter in the subsample of core ETGs when compared to cusp ETGs. In core ETGs (old, passively evolving stellar systems) MTOT is significantly larger than the total stellar mass MSTAR and the correlation with the hot gas properties is driven by their dark matter mass MDM. Cusp ETGs typically have lower LX,GAS than core ETGs. In cusp ETGs, for a given MDM, higher LX,GAS is associated with higher MSTAR, suggesting stellar feedback as an important secondary factor for heating the ISM. Using the MGCS-MTOT scaling relations we compare 272 ETGs with previous estimates of the stellar-to-halo-mass relation of galaxies. Our model-independent estimate of MTOT results in a good agreement around halo masses of 1012 M☉, but suggests higher star formation efficiency than usually assumed both at the low- and at the high-halo-mass ends.
