NGC 5626: a massive fast rotator with a twist

TL;DR

This study analyzes the massive elliptical galaxy NGC 5626, revealing it as a rare fast rotator with a significant kinematic twist, and discusses its possible formation through a galaxy merger.

Contribution

It provides a detailed kinematic analysis of NGC 5626 using MUSE data, highlighting its rarity and the potential of MUSE to discover similar galaxies.

Findings

NGC 5626 is a massive fast rotator with a strong kinematic twist.

Such large-scale kinematic twists may be underdetected in previous surveys.

A merger between the Milky Way and Andromeda could produce a galaxy like NGC 5626.

Abstract

We present a kinematic analysis of the dust-lane elliptical NGC 5626 based on MUSE observations. These data allow to robustly classify this galaxy as a fast rotator and to infer a virial mass of $10^{11.7} M_\odot$, making it one of the most massive fast rotators known. In addition, the depth and extent of the MUSE data reveal a strong kinematic twist in the stellar velocity field (by up to $45$ degrees beyond $1.5R_e$). A comparison with the ATLAS$^\mathrm{3D}$ sample underlines the rareness of this system, although we show that such a large-scale kinematic twist could have been missed by the ATLAS$^\mathrm{3D}$ data due to the limited spatial sampling of this survey (typically extending to $0.6R_e$ for massive ETGs). MUSE thus has the potential to unveil more examples of this type of galaxies. We discuss the environment and possible formation history of NGC 5626 and finally argue how a merger between the Milky Way and Andromeda could produce a galaxy of the same class as NGC 5626.