Isolated compact elliptical galaxies: Stellar systems that ran away

TL;DR

This study uncovers 195 isolated compact elliptical galaxies, showing they are tidally stripped systems ejected from their hosts, challenging previous notions of their formation.

Contribution

The paper identifies a large population of isolated compact elliptical galaxies and demonstrates their origin as ejected tidally stripped systems through dynamical analysis.

Findings

Found 195 isolated compact elliptical galaxies across various environments.

Dynamical analysis supports their ejection from host clusters via three-body encounters.

Isolated cE galaxies are confirmed as tidally stripped systems that ran away from hosts.

Abstract

Compact elliptical galaxies form a rare class of stellar system (~30 presently known) characterized by high stellar densities and small sizes and often harboring metal-rich stars. They were thought to form through tidal stripping of massive progenitors, until two isolated objects were discovered where massive galaxies performing the stripping could not be identified. By mining astronomical survey data, we have now found 195 compact elliptical galaxies in all types of environment. They all share similar dynamical and stellar population properties. Dynamical analysis for nonisolated galaxies demonstrates the feasibility of their ejection from host clusters and groups by three-body encounters, which is in agreement with numerical simulations. Hence, isolated compact elliptical and isolated quiescent dwarf galaxies are tidally stripped systems that ran away from their hosts.