The MASSIVE Survey IV.: The X-ray halos of the most massive early-type
  galaxies in the nearby Universe
  Studies of the physical properties of local elliptical galaxies (e.g., gas
temperatures, halo masses, stellar kinematics) are shedding new light on galaxy
formation. Here we present the hot X-ray gas properties of 33 early-type
systems within the MASSIVE galaxy survey sample that have archival Chandra
X-ray observations. Through careful X-ray spectral modeling, we derive X-ray
luminosities (L_X) and plasma temperatures (T_gas) for the diffuse gas
components in these galaxies. We combine the MASSIVE sample with 41 galaxies
from the ATLAS^3D survey to investigate the X-ray and optical properties of a
statistically significant sample of nearby early-type galaxies across a
wide-range of environments. We deduce that all early-type galaxies (independent
of galaxy mass and rotational support) follow a universal scaling law such that
L_X~T_gas^4.5. When X-ray measurements are performed consistently in apertures
set by the galaxy stellar content, the wide-scale environment does not
contribute to the intrinsic scatter (~0.5dex) within the scaling relation. We
further demonstrate that the scatter in L_X around both K-band luminosity (L_K)
and the galaxy stellar velocity dispersion is primarily driven by T_gas, with
no clear trends with halo mass, radio power, or angular momentum of the stars.
It is not trivial to tie the origin of the gas directly to either the stellar
mass or the galaxy potential. Indeed, our data require a steeper relation
between L_X, L_K, and sigma_e than predicted by standard mass-loss models.
Finally, we find a statistically significant correlation between sigma_e and
T_gas, suggesting that T_gas is set by the galaxy potential inside the optical
effective radius. We conclude that within the inner-most 10-30kpc region,
early-types maintain pressure-supported hot gas, with a minimum T_gas set by
the virial temperature, but the majority show evidence for some additional
heating.
