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Accepted manuscript

WALLABY Pilot Survey: kNN identification of perturbed galaxies through Hi morphometrics

Published online by Cambridge University Press:  24 January 2025

Benne W. Holwerda Open the ORCID record for Benne W. Holwerda [Opens in a new window] ,
Helga Dénes Open the ORCID record for Helga Dénes [Opens in a new window] ,
Jonghwan Rhee ,
Denis Leahy Open the ORCID record for Denis Leahy [Opens in a new window] ,
Bärbel S. Koribalski Open the ORCID record for Bärbel S. Koribalski [Opens in a new window] ,
Niankun Yu ,
Nathan Deg Open the ORCID record for Nathan Deg [Opens in a new window] ,
Tobias Westmeier Open the ORCID record for Tobias Westmeier [Opens in a new window] ,
Karen Lee-Wadde Open the ORCID record for Karen Lee-Wadde [Opens in a new window]  and
Yago Ascasibar
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Benne W. Holwerda*
Affiliation:
University of Louisville, Department of Physics and Astronomy, 102 Natural Science Building, 40292 KY Louisville, USA.
Helga Dénes
Affiliation:
School of Physical Sciences and Nanotechnology, Yachay Tech University, Hacienda San José S/N, 100119, Urcuquí, Ecuador
Jonghwan Rhee
Affiliation:
International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia
Denis Leahy
Affiliation:
University of Calgary, Department of Physics and Astronomy, 2500 University Dr. NW, Calgary, AB, Canada, T2N 1N4
Bärbel S. Koribalski
Affiliation:
Australia Telescope National Facility, CSIRO, Space and Astronomy, P.O. Box 76, NSW 1710, Australia School of Science, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751, Australia
Niankun Yu
Affiliation:
National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, People’s Republic of China Key Laboratory of Radio Astronomy and Technology, Chinese Academy of Sciences, Beijing 100101, People’s Republic of China
Nathan Deg
Affiliation:
Department of Physics, Engineering Physics, and Astronomy, Queen’s University, Kingston, ON, K7L 3N6, Canada
Tobias Westmeier
Affiliation:
International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia
Karen Lee-Wadde
Affiliation:
Australian SKA Regional Centre Departamento de Física Teórica, Universidad Autónoma de Madrid (UAM), Madrid 28049, Spain
Yago Ascasibar
Affiliation:
Departamento de Física Teórica, Universidad Autónoma de Madrid (UAM), Madrid 28049, Spain Centro de Investigación Avanzada en Física Fundamental (CIAFF-UAM), Madrid 28049, Spain
Manasvee Saraf
Affiliation:
International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia Australia Telescope National Facility, CSIRO, Space and Astronomy, P.O. Box 1130, Bentley, WA 6102, Australia ARC Centre of Excellence for All-Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia
Xuchen Lin
Affiliation:
Department of Astronomy, School of Physics, Peking University, Beijing 100871, People’s Republic of China
Barbara Catinella
Affiliation:
ARC Centre of Excellence for All-Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia International Centre for Radio Astronomy Research, The University of Western Australia, Crawley, WA 6009, Australia
Kelley Hess
Affiliation:
Chalmers University of Technology, Onsala Space Observatory, Göteborg, Sweden
*
Author for correspondence: B.W. Holwerda, Email: benne.holwerda@louisville.edu.
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Abstract

Galaxy morphology in stellar light can be described by a series of “non-parametric” or “morphometric” parameters, such as concentrationasymmetry-smoothness, Gini, M20, and Sersic fit. These parameters can be applied to column density maps of atomic hydrogen (Hi). The Hi distribution is susceptible to perturbations by environmental effects, e.g. inter-galactic medium pressure and tidal interactions. Therefore, Hi morphology can potentially identify galaxies undergoing ram-pressure stripping or tidal interactions. We explore three fields in theWALLABY Pilot Hi survey and identify perturbed galaxies based on a k-nearest Neighbor (kNN) algorithm using an Hi morphometric feature space. For training, we used labeled galaxies in the combined NGC 4808 and NGC 4636 fields with six Hi morphometrics to train and test a kNN classifier. The kNN classification is proficient in classifying perturbed galaxies with all metrics –accuracy, precision and recall– at 70-80%. By using the kNN method to identify perturbed galaxies in the deployment field, the NGC 5044 mosaic, we find that in most regards, the scaling relations of perturbed and unperturbed galaxies have similar distribution in the scaling relations of stellar mass vs star formation rate and the Baryonic Tully-Fisher relation, but the Hi and stellar mass relation flatter than of the unperturbed galaxies. Our results for NGC 5044 provide a prediction for future studies on the fraction of galaxies undergoing interaction in this catalogue and to build a training sample to classify such galaxies in the fullWALLABY survey.

Keywords

galaxies: evolutionGalaxies galaxies: interactionsGalaxies galaxies: ISMGalaxies galaxies: structureGalaxies
Type
Research Article
Information
Publications of the Astronomical Society of Australia , Accepted manuscript , pp. 1 - 21
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of Astronomical Society of Australia

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