The Many Assembly Histories of Massive Void Galaxies as Revealed by Integral Field Spectroscopy

TL;DR

This study uses integral field spectroscopy to explore the diverse assembly histories of nine massive void galaxies, revealing varied morphologies, merger activities, and stellar populations, with ongoing minor mergers influencing their evolution.

Contribution

First detailed integral field spectroscopy analysis of massive void galaxies, highlighting their diverse assembly histories and the role of minor mergers in their ongoing evolution.

Findings

Most galaxies are evolving secularly with low star formation rates.

Some galaxies show disturbed morphologies indicating ongoing minor mergers.

Massive void galaxies are predominantly red and discy, with some in transition to early types.

Abstract

We present the first detailed integral field spectroscopy study of nine central void galaxies with M*>10^10 Msun using the Wide Field Spectrograph (WiFeS) to determine how a range of assembly histories manifest themselves in the current day Universe. While the majority of these galaxies are evolving secularly, we find a range of morphologies, merger histories and stellar population distributions, though similarly low Halpha-derived star formation rates (<1 Msun/yr). Two of our nine galaxies host AGNs, and two have kinematic disruptions to their gas that are not seen in their stellar component. Most massive void galaxies are red and discy, which we attribute to a lack of major mergers. Some have disturbed morphologies and may be in the process of evolving to early-type thanks to ongoing minor mergers at present times, likely fed by tendrils leading off filaments. The diversity in our small galaxy sample, despite being of similar mass and environment means that these galaxies are still assembling at present day, with minor mergers playing an important role in their evolution. We compare our sample to a mass and magnitude-matched sample of field galaxies, using data from the Sydney-AAO Multi-object Integral field spectrograph (SAMI) galaxy survey. We find that despite environmental differences, galaxies of mass M*>10^10 Msun have similarly low star formation rates (<3 Msun/yr). The lack of distinction between the star formation rates of the void and field environments points to quenching of massive galaxies being a largely mass-related effect.