THE MASSIVE SURVEY. IV. THE X-RAY HALOS OF THE MOST MASSIVE EARLY-TYPE GALAXIES IN THE NEARBY UNIVERSE

Abstract

Studies of the physical properties of local elliptical galaxies are shedding new light on galaxy formation. Here we present the hot-gas properties of 33 early-type systems within the MASSIVE galaxy survey that have archival Chandra X-ray observations, and we use these data to derive X-ray luminosities ( ) and plasma temperatures ( ) for the diffuse gas components. We combine this with the survey to investigate the X-ray–optical properties of a statistically significant sample of early-type galaxies across a wide range of environments. When X-ray measurements are performed consistently in apertures set by the galaxy stellar content, we deduce that all early types (independent of galaxy mass, environment, and rotational support) follow a universal scaling law such that . We further demonstrate that the scatter in around both K -band luminosity ( L K ) and the galaxy stellar velocity dispersion ( ) is primarily driven by , with no clear trends with halo mass, radio power, or angular momentum of the stars. It is not trivial to tie the gas origin directly to either stellar mass or galaxy potential. Indeed, our data require a steeper relation between , and than predicted by standard mass-loss models. Finally, we find that is set by the galaxy potential inside the optical effective radius. We conclude that within the innermost 10–30 kpc region, early types maintain pressure-supported hot gas, with a minimum set by the virial temperature, but the majority show evidence for additional heating.