X-Ray Halos of Early-type Galaxies with Active Galactic Nucleus Feedback and Accretion from a Circumgalactic Medium: Models and Observations

Knowledge of the X-ray properties of the hot-gas halos of early-type galaxies (ETGs) has significantly advanced in the past years, for large and homogeneously investigated samples. We compare these results with the X-ray properties of an exploratory set of gas evolution models in realistic ETGs, produced with our high-resolution 2D hydrodynamical code MACER that includes active galactic nucleus feedback and accretion from a circumgalactic medium. The model X-ray emission and absorption are integrated along the line of sight, to obtain maps of the surface brightness Sigma X and temperature TX. The X-ray diagnostics considered are the luminosity and average temperature for the whole galaxy (LX and < TX >) and within five optical effective radii (LX,5 and < TX,5 >) and the circularized profiles Sigma X(R) and TX(R). The values for LX, LX,5, < TX >, and < TX,5 > compare very well with those observed. The Sigma X(R) and TX(R) also present qualitative similarities with those of the representative galaxy NGC 5129 and those of ETGs with the most commonly observed shape for TX(R): Sigma X(R) matches the observed profile over many optical effective radii Re, and TX(R) reproduces the characteristic bump that peaks at R = (1 divided by 3)Re. Inside the peak position, TX(R) declines toward the center, but the explored models are systematically hotter by similar or equal to 30%; possible explanations for this discrepancy are discussed. Interestingly, Sigma X(R) and TX(R) as large as those observed outside R similar or equal to Re are reproduced only with significant accretion from a circumgalactic medium, highlighting its importance.