The merger fraction of post-starburst galaxies in UNIONS

Post-starburst (PSB) galaxies are defined as having experienced a recent burst of star formation, followed by a prompt truncation in further activity. Identifying the mechanism(s) causing a galaxy to experience a post-starburst phase therefore provides integral insight into the causes of rapid quenc...

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Bibliographic Details
Published in:arXiv.org 2022-07
Main Authors: Wilkinson, Scott, Ellison, Sara L, Connor Bottrell, Bickley, Robert W, Gwyn, Stephen, Jean-Charles Cuillandre, Wild, Vivienne
Format: Article
Language:English
Subjects:
Artificial neural networks
Classification
Digital imaging
Galaxy mergers & collisions
Identification methods
Morphology
Rapid quenching (metallurgy)
Sky surveys (astronomy)
Star & galaxy formation
Star formation
Starburst galaxies
Starbursts
Stars & galaxies
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Summary:Post-starburst (PSB) galaxies are defined as having experienced a recent burst of star formation, followed by a prompt truncation in further activity. Identifying the mechanism(s) causing a galaxy to experience a post-starburst phase therefore provides integral insight into the causes of rapid quenching. Galaxy mergers have long been proposed as a possible post-starburst trigger. Effectively testing this hypothesis requires a large spectroscopic galaxy survey to identify the rare PSBs as well as high quality imaging and robust morphology metrics to identify mergers. We bring together these critical elements by selecting PSBs from the overlap of the Sloan Digital Sky Survey and the Canada-France Imaging Survey and applying a suite of classification methods: non-parametric morphology metrics such as asymmetry and Gini-M20, a convolutional neural network trained to identify post-merger galaxies, and visual classification. This work is therefore the largest and most comprehensive assessment of the merger fraction of PSBs to date. We find that the merger fraction of PSBs ranges from 19% to 42% depending on the merger identification method and details of the PSB sample selection. These merger fractions represent an excess of 3-46x relative to non-PSB control samples. Our results demonstrate that mergers play a significant role in generating PSBs, but that other mechanisms are also required. However, applying our merger identification metrics to known post-mergers in the IllustrisTNG simulation shows that ~70% of recent post-mergers (
ISSN:2331-8422
DOI:10.48550/arxiv.2207.04152