Star formation characteristics of CNN-identified post-mergers in the Ultraviolet Near Infrared Optical Northern Survey (UNIONS)
Abstract
The importance of the post-merger epoch in galaxy evolution has been well documented, but post-mergers are notoriously difficult to identify. While the features induced by mergers can sometimes be distinctive, they are frequently missed by visual inspection. In addition, visual classification efforts are highly inefficient because of the inherent rarity of post-mergers (~1 per cent in the low-redshift Universe), and non-parametric statistical merger selection methods do not account for the diversity of post-mergers or the environments in which they appear. To address these issues, we deploy a convolutional neural network (CNN) that has been trained and evaluated on realistic mock observations of simulated galaxies from the IllustrisTNG simulations, to galaxy images from the Canada France Imaging Survey, which is part of the Ultraviolet Near Infrared Optical Northern Survey. We present the characteristics of the galaxies with the highest CNN-predicted post-merger certainties, as well as a visually confirmed subset of 699 post-mergers. We find that post-mergers with high CNN merger probabilities [p(x) > 0.8] have an average star formation rate that is 0.1 dex higher than a mass- and redshift-matched control sample. The SFR enhancement is even greater in the visually confirmed post-merger sample, a factor of 2 higher than the control sample.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jun 02, 2022
- Source ID
- 10.1093/mnras/stac1500
Entities
People
- Connor Bottrell
- David R. Patton
- Michael J. Hudson
- Robert W. Bickley
- Sara Ellison
- Stephen Gwyn
Organizations
- Alfred P. Sloan Foundation
- American Museum of Natural History
- California Earthquake Authority
- Canadian Space Agency
- Case Western Reserve University
- Chinese Academy of Sciences
- Compute Canada
- Drexel University
- Herzberg Institute of Astrophysics
- Higher Education Funding Council for England
- Institute for Advanced Study
- Institute for the Physics and Mathematics of the Universe
- Johns Hopkins University
- Los Alamos National Laboratory
- Max Planck Society
- National Aeronautics and Space Administration
- National Center for Scientific Research
- National Research Council
- National Science Foundation
- New Mexico State University
- Ohio State University
- Perimeter Institute for Theoretical Physics
- Princeton University
- Trent University
- United States Department of Energy
- United States Naval Observatory
- University of Basel
- University of Cambridge
- University of Chicago
- University of Hawaiʻi System
- University of Pittsburgh
- University of Portsmouth
- University of Victoria
- University of Washington
- University of Waterloo