Work

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

Year: 2025

Type: article

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 ΣX 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 ΣX(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 ΣX(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): ΣX(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, ΣX(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.

Source: The Astrophysical Journal

DOI: 10.3847/1538-4357/adf5c1

Authors: Silvia Pellegrini, Luca Ciotti, Zhaoming Gan, Dong-Woo Kim, Jeremiah P. Ostriker