Chandra survey of nearby highly inclined disc galaxies - III. Comparison with hydrodynamical simulations of circumgalactic coronae

Abstract

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 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 intergalactic gas. We confirm the existing conclusion that this pure accretion model substantially overpredicts 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 supernovae feedback and yield galaxies that 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, for example, the absence of active galactic nuclei feedback, and possibly the adoption of constant stellar feedback parameters. The simulated galaxies exhibit a tight correlation (with little scatter) between coronal luminosity and halo mass. Having inferredM200 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 ofM* ̃ 2× 1011M⊙ orM200 ̃ 1013M⊙ tend to have higher LX/M* and LX/M200 than low-mass counterparts, indicating that the accretion of intergalactic gas plays an increasingly important role in establishing the observable hot circumgalactic medium with increasing galaxy mass. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.