Searching for a Gravitational Heating Signature in Nearby Luminous Ellipticals

TL;DR

This study investigates whether gravitational interactions in nearby luminous elliptical galaxies can heat their interstellar medium, using deep optical imaging to identify tidal disturbances and analyze their potential impact on ISM temperature regulation.

Contribution

It provides the first statistical analysis of tidal disturbance signatures in a complete sample of ellipticals, linking gravitational interactions to ISM heating.

Findings

73% of galaxies show tidal disturbances

Ellipticals continue to evolve through gravitational interactions

Potential link between interactions and ISM heating

Abstract

We present a new deep optical study of a luminosity limited sample of nearby elliptical galaxies, attempting to observe the effects of gravitational interactions on the ISM of these objects. This study is motivated by recent observations of M86, a nearby elliptical galaxy that shows possible evidence for gas heating through a recent gravitational interaction. The complete sample includes luminous ellipticals in clusters, groups and the field. For each of the galaxies we objectively derive a tidal parameter which measures the deviation of the stellar body from a smooth, relaxed model and find that 73% of them show tidal disturbance signatures in their stellar bodies. This is the first time that such an analysis is done on a statistically complete sample and it confirms that elliptical galaxies continue to grow and evolve through gravitational interactions even in the local Universe. Our study of ellipticals in a wide range of interaction stages, along with available ISM data will attempt to shed light on this possibly alternative mechanism for maintaining the observed ISM temperatures of elliptical galaxies.