2025ApJ...990..194P

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.