The effects of galaxy shape and rotation on the X-ray haloes of early-type galaxies – II. Numerical simulations

Abstract

By means of high-resolution 2D hydrodynamical simulations, we study the evolution of the hot interstellar medium (ISM) for a large set of early-type galaxy models, characterized by various degrees of flattening and internal rotation. The galaxies are described by state-of-the-art axisymmetric two-component models, tailored to reproduce real systems; the dark matter haloes follow the Navarro–Frenk–White or the Einasto profile. The gas is produced by the evolving stars, and heated by Type Ia supernovae. We find that, in general, the rotation field of the ISM in rotating galaxies is very similar to that of the stars, with a consequent negligible heating contribution from thermalization of the ordered motions. The relative importance of flattening and rotation in determining the final X-ray luminosity LX and temperature TX of the hot haloes is a function of the galactic mass. Flattening and rotation in low-mass galaxies favour the establishment of global winds, with the consequent reduction of LX. In medium- to high-mass galaxies, flattening and rotation are not sufficient to induce global winds; however, in the rotating models, the nature of the gas flows is deeply affected by conservation of angular momentum, resulting in a reduction of both LX and TX.