Chandra Survey of Nearby Highly Inclined Disc Galaxies - III: Comparison   with Hydrodynamical Simulations of Circumgalactic Coronae
  X-ray observations of circumgalactic coronae provide a valuable means by which to test galaxy formation theories. Two primary mechanisms are thought to be responsible for the establishment of such coronae: accretion of intergalactic gas (IGM) and/or galactic feedback. In this paper, we first compare our Chandra sample of galactic coronae of 53 nearby highly-inclined disc galaxies to an analytical model considering only the accretion of IGM. We confirm the existing conclusion that this pure accretion model substantially over-predicts the coronal emission. We then select 30 field galaxies from our original sample, and correct their coronal luminosities to uniformly compare them to deep X-ray measurements of several massive disc galaxies from the literature, as well as to a comparable sample of simulated galaxies drawn from the Galaxies-Intergalactic Medium Interaction Calculation (GIMIC). These simulations explicitly model both accretion and SNe feedback and yield galaxies exhibit X-ray properties in broad agreement with our observational sample. However, notable and potentially instructive discrepancies exist between the slope and scatter of the Lx-M200 and Lx-SFR relations, highlighting some known shortcomings of GIMIC, e.g., the absence of AGN feedback, and possibly the adoption of constant stellar feedback parameters. The simulated galaxies exhibit a tight Lx-M200 correlation with little scatter. Having inferred M200 for our observational sample via the Tully-Fisher relation, we find a weaker and more scattered correlation. In the simulated and observed samples alike, massive non-starburst galaxies above a typical transition mass of M*~2e11Msun or M200~1e13Msun tend to have higher Lx/M* and Lx/M200 than low-mass counterparts, indicating that the accretion of IGM plays an increasingly important role in establishing the observable hot circumgalactic medium with increasing galaxy mass. 
Jiang-Tao Li (CEA/UMASS/NJU), Robert A. Crain (Leiden Observatory),   and Q. Daniel Wang (UMASS)
astro-ph.CO astro-ph.GA astro-ph.HE