Old and New Major Mergers in the SOSIMPLE galaxy, NGC 7135

TL;DR

This study uses high-resolution spectroscopy and spectral fitting to analyze NGC 7135, revealing signs of ongoing and past mergers through kinematic and chemical signatures, including a gradient in accreted material.

Contribution

It provides the first detailed spatially-resolved analysis of merger history in NGC 7135 using MUSE data, identifying both recent and ancient merger signatures.

Findings

NGC 7135 shows signs of an ongoing merger with counter-rotating gas.

Evidence of an older merger event 6-10 Gyr ago is detected.

The accreted stellar material increases with galactocentric radius, reaching ~7% at 0.6 effective radii.

Abstract

The simultaneous advancement of high resolution integral field unit spectroscopy and robust full-spectral fitting codes now make it possible to examine spatially-resolved kinematic, chemical composition, and star-formation history from nearby galaxies. We take new MUSE data from the Snapshot Optical Spectroscopic Imaging of Mergers and Pairs for Legacy Exploration (SOSIMPLE) survey to examine NGC 7135. With counter-rotation of gas, disrupted kinematics and asymmetric chemical distribution, NGC 7135 is consistent with an ongoing merger. Though well hidden by the current merger, we are able to distinguish stars originating from an older merger, occurring 6-10 Gyr ago. We further find a gradient in ex-situ material with galactocentric radius, with the accreted fraction rising from 0% in the galaxy centre, to ~7% within 0.6 effective radii.