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

TL;DR

This study calibrates the relation between total galaxy mass and globular cluster system mass in early-type galaxies, confirming M_GCS as an effective proxy for M_TOT and exploring its connection with X-ray properties and dark matter.

Contribution

It provides a new calibration of the M_GCS-M_TOT relation in early-type galaxies and demonstrates its effectiveness as a proxy, also analyzing its connection with X-ray and dark matter properties.

Findings

M_GCS correlates nearly linearly with M_TOT in early-type galaxies.

M_TOT is significantly larger than stellar mass in core ETGs, driven by dark matter.

Cusp ETGs show lower X-ray luminosity than core ETGs, with stellar feedback influencing ISM heating.

Abstract

Using globular cluster (GC) kinematics and photometry data, we calibrate the scaling relation between the total galaxy mass (M_TOT including dark matter) and total globular cluster system mass (M_GCS) in a sample of 30 early-type galaxies (ETG), 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 M_TOT and the ISM X-ray luminosity and temperature, respectively. We confirm that M_GCS can be effectively used as a proxy of M_TOT. We further find that the L_X,GAS - M_TOT relation is far tighter in the subsample of core ETGs, when compared to cusp ETGs. In core ETGs (old, passively evolving stellar systems) M_TOT is significantly larger than the total stellar mass M_STAR and the correlation with the hot gas properties is driven by their dark matter mass M_DM. Cusp ETGs have typically lower LX,GAS than core ETGs. In cusp ETGs, for a given M_DM, higher L_X,GAS is associated with higher M_STAR, suggesting stellar feedback as an important secondary factor for heating the ISM. Using the M_GCS- M_TOT scaling relations we compare 272 ETGs with previous estimates of the stellar-to-halo mass relation of galaxies. Our model-independent estimate of M_TOT results in a good agreement around halo masses of 10^12 Mo, but suggest higher star formation efficiency than usually assumed both at the low and at the high halo mass ends.