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 (L X,gas ) and plasma temperatures (T gas ) for the diffuse gas components. We combine this with the ATLAS 3D 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 µL T X,gas gas 4.5 . We further demonstrate that the scatter in L X,gas around both K-band luminosity (L K ) and the galaxy stellar velocity dispersion (s e ) 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 gas origin directly to either stellar mass or galaxy potential. Indeed, our data require a steeper relation between L L , K X,gas , and s e than predicted by standard mass-loss models. Finally, we find that T gas 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 T gas set by the virial temperature, but the majority show evidence for additional heating.

The MASSIVE Survey. VI. The Spatial Distribution and Kinematics of Warm Ionized Gas in the Most Massive Local Early-type Galaxies

“…However, with only redshifted emission, we cannot rule out an inflow, rotation, or simply an ongoing merger. We do detect a compact radio source (K. Nyland et al in preparation) and a soft nuclear X-ray source (Goulding et al 2016) in the center. Since we do not detect Hβ we cannot say much about the nuclear line ratios.…”

“…The relationship between the warm ionized and hot X-ray-emitting gas is still unclear (e.g., Forman et al 1985;H e c k m a ne ta l .1989; Macchetto et al 1996;Goudfrooij 1999;Sarzi et al 2013;Goulding et al 2016),andwe have approved Chandra time (PI: Goulding) to increase the MASSIVE sample with hot gas measurements. Similarly, the occurrence rate of warm ionized gas (and dust) as a function of radio continuum detection may reveal relationships to accreting supermassive black holes and the presence of central dust disks; this will be explored in a future study.…”

“…This paper represents part of our comprehensive effort to study gas of all phases in the MASSIVE sample, including using CO to trace molecular gas (Davis et al 2016) as well as hot X-ray gas (Goulding et al 2016).…”

Hot Gaseous Halos in Early Type Galaxies

“…X-ray scaling relations have been widely used to investigate the origin and evolution of the hot ISM of ETGs [1][2][3][4]. Recent numerical simulation studies [5][6][7][8] have further attempted to reproduce the observed scaling relations, in order to constrain the physical mechanisms that shape the hot ISM.…”

“…This relation is tighter than the L X,GAS -L K relation and may indicate virialization of the hot gas in the dark matter halos. The best fit relation is L X,GAS~TGAS 4.5 [1,3,4] when the cD galaxies are excluded. The relation is particularly tight for the normal (non-cD) core galaxies with a scatter of only 0.2 dex rms.…”