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

Abstract 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 Σ X and temperature T X . The X-ray diagnostics considered are the luminosity and average temperature for the whole galaxy ( L X and 〈 T X 〉) and within five optical effective radii ( L X,5 and 〈 T X,5 〉) and the circularized profiles Σ X ( R ) and T X ( R ). The values for L X , L X,5 , 〈 T X 〉, and 〈 T X,5 〉 compare very well with those observed. The Σ X ( R ) and T X ( R ) also present qualitative similarities with those of the representative galaxy NGC 5129 and those of ETGs with the most commonly observed shape for T X ( R ): Σ X ( R ) matches the observed profile over many optical effective radii R e , and T X ( R ) reproduces the characteristic bump that peaks at R = (1 ÷ 3) R e . Inside the peak position, T X ( R ) declines toward the center, but the explored models are systematically hotter by ≃30%; possible explanations for this discrepancy are discussed. Interestingly, Σ X ( R ) and T X ( R ) as large as those observed outside R ≃ R e are reproduced only with significant accretion from a circumgalactic medium, highlighting its importance.