2013ApJ...776..116K

We have revisited the X-ray scaling relations of early-type galaxies (ETG) by investigating, for the first time, the L_X,Gas-M_Totalrelation in a sample of 14 ETGs. In contrast to the large scatter (a factor of 10²-10³) in the L_X,Total-L_Brelation, we found a tight correlation between these physically motivated quantities with an rms deviation of a factor of three in L_X,Gas= 10³⁸-10⁴³ erg/s or M_Total= a fewx10¹⁰ to a fewx10¹² M_☉. More striking, this relation becomes even tighter with an rms deviation of a factor of 1.3 among the gas-rich galaxies (with L_X,Gas> 10⁴⁰ erg/s). In a simple power-law form, the new relation is (L_X,Gas/10⁴⁰ erg/s) = (M_Total/3.2x10¹¹ M_☉)³. This relation is also consistent with the steep relation between the gas luminosity and temperature, L_X,Gas∼ T_Gas^4.5, identified by Boroson et al., if the gas is virialized. Our results indicate that the total mass of an ETG is the primary factor in regulating the amount of hot gas. Among the gas-poor galaxies (with L_X,Gas< a fewx10³⁹ erg/s), the scatter in the L_X,Gas-M_Total(and L_X,Gas-T_Gas) relation increases, suggesting that secondary factors (e.g., rotation, flattening, star formation history, cold gas, environment, etc.) may become important.