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.
