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arXiv · 2509.03153

A comprehensive catalogue of OB cluster candidates in M31 and their association with giant molecular clouds

Yuan Liang·Guang-Wei Li·Chao-Wei Tsai·Jingwen Wu
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Abstract

We present a new catalogue of 578 OB cluster (OBC) candidates in the Andromeda galaxy (M31), identified using a MeanShift-based algorithm on HST's F275W-band imaging from the PHAT (Dalcanton et al. 2012) and PHAST (Chen et al. 2025) Hubble surveys. These clusters exhibit typical half-light radii of 1-2 pc and strong ultraviolet luminosities indicative of recent massive star formation. Spatial analysis reveals a pronounced north-south asymmetry: clusters in the northern disc show tight associations with giant molecular clouds (GMCs), while southern clusters appear more compact and luminous but less correlated with molecular gas. Two-point correlation functions demonstrate significant clustering of OBC candidates on scales 100 pc and a strong spatial association with GMCs, consistent with hierarchical star formation in dense gas-rich environments. These findings offer new constraints on the early evolution and feedback-driven dispersal of young stellar clusters across galactic discs.

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Yuan Liang, Guang-Wei Li, Chao-Wei Tsai, Jingwen Wu. 2025-09-03. A comprehensive catalogue of OB cluster candidates in M31 and their association with giant molecular clouds. https://doi.org/10.1093/mnras%2Fstaf1317

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