Cusp-core dichotomy of elliptical galaxies: the role of thermal evaporation

TL;DR

This paper proposes that thermal evaporation of cold gas by hot interstellar medium explains the cusp-core dichotomy in elliptical galaxies, linking galaxy mass and hot gas content to their central brightness profiles.

Contribution

It introduces a thermal evaporation model as the mechanism behind the cusp-core dichotomy, connecting galaxy properties with their central surface-brightness profiles.

Findings

Cusp galaxies are less massive and hot-gas poor, often refilled by starbursts.

Core galaxies are more massive and hot-gas rich, with cold gas eliminated.

The model aligns with observed differences in luminosity, X-ray content, and stellar populations.

Abstract

There are two families of luminous elliptical galaxies: cusp galaxies, with steep central surface-brightness profiles, and core galaxies, whose surface-brightness profiles have flat central cores. Thermal evaporation of accreted cold gas by the hot interstellar medium may be at the origin of this cusp-core dichotomy: in less massive (hot-gas poor) galaxies central cores are likely to be refilled by central starbursts following cold gas infall, while in more massive (hot-gas rich) galaxies most cold gas is eliminated and central cores survive. This scenario is consistent with the observation that cusp and core galaxies differ systematically in terms of optical luminosity, X-ray gas content, age of the central stellar population, and properties of the active galactic nucleus.