WALLABY Pilot Survey: hydra cluster galaxies UV and H I morphometrics

Benne W. Holwerda, Frank Bigiel, Albert Bosma, Helene M. Courtois, Nathan Deg, Helga Dénes, Ahmed Elagali, Bi Qing For, Baerbel Koribalski, Denis A. Leahy, Karen Lee-Waddell, Ángel R. López-Sánchez, Se Heon Oh, Tristan N. Reynolds, Jonghwan Rhee, Kristine Spekkens, Jing Wang, Tobias Westmeier, O. Ivy Wong

Research output: Contribution to journalArticlepeer-review


Galaxy morphology in atomic hydrogen (H I) and in the ultraviolet (UV) are closely linked. This has motivated their combined use to quantify morphology over the full H I disc for both H I and UV imaging. We apply galaxy morphometrics: concentration, asymmetry, gini, M20 and multimode-intensity-deviation statistics to the first moment-0 maps of the WALLABY Survey of galaxies in the hydra cluster centre. Taking advantage of this new H I survey, we apply the same morphometrics over the full H I extent on archival GALEX FUV and NUV data to explore how well H I truncated, extended ultraviolet disc (XUV) and other morphological phenomena can be captured using pipeline WALLABY data products. Extended H I and UV discs can be identified relatively straightforward from their respective concentration. Combined with WALLABY H I, even the shallowest GALEX data are sufficient to identify XUV discs. Our second goal is to isolate galaxies undergoing ram-pressure stripping in the H I morphometric space. We employ four different machine learning techniques, a decision tree, a k-nearest neighbour, a support-vector machine, and a random forest. Up to 80 per cent precision and recall are possible with the random forest giving the most robust results.

Original languageEnglish
Pages (from-to)1502-1517
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Publication statusPublished - 1 May 2023

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