The PHANGS-MUSE/HST-Halpha Nebulae Catalogue
Abstract
We present the PHANGS-MUSE/HST-Halpha nebulae catalogue, comprising 5177 spatially resolved nebulae across 19 nearby star-forming galaxies (< 20 Mpc), based on high-resolution Halpha imaging from HST, homogenised to a fixed 10 pc resolution and sensitivity. Combined with MUSE spectroscopy, this enables robust classification of 4882 H II regions and separation of planetary nebulae and supernova remnants. Electron densities for 2544 H II regions are derived using [S II] diagnostics, and nebular sizes measured via circularised radii and second moments yield a median of 20 pc, extending to sub-parsec scales. A structural complexity score traces substructure, showing that about a third of regions are H II complexes, with a higher fraction in galaxy centres. A luminosity-size relation calibrated from the HST sample is applied to 30,790 MUSE nebulae, recovering sizes down to 1 pc. Observed sizes exceed classical Stromgren radii, implying typical volume filling factors of 0.22. We associate 3349 H II regions with stellar populations from PHANGS-HST, finding median ages of 3 Myr and masses of 4-5 log(Msun). The dataset provides a detailed, spatially resolved link between nebular structure and ionising sources, serving as a benchmark for future studies of feedback, diffuse ionised gas, and star formation regulation in the interstellar medium. The full catalogue is made publicly available in machine-readable format.
Cite
@article{arxiv.2510.11778,
title = {The PHANGS-MUSE/HST-Halpha Nebulae Catalogue},
author = {A. T. Barnes and R. Chandar and K. Kreckel and F. Belfiore and D. Pathak and D. Thilker and A. K. Leroy and B. Groves and S. C. O. Glover and R. McClain and A. Amiri and Z. Bazzi and M. Boquien and E. Congiu and D. A. Dale and O. V. Egorov and E. Emsellem and K. Grasha and J. Gonzalez Lobos and K. Henny and H. He and R. Indebetouw and J. C. Lee and J. Li and F. -H. Liang and K. Larson and D. Maschmann and S. E. Meidt and J. E. Méndez-Delgado and J. Neumann and H. -A. Pan and M. Querejeta and E. Rosolowsky and S. K. Sarbadhicary and F. Scheuermann and L. Úbeda and T. G. Williams and T. D. Weinbeck and B. Whitmore and A. Wofford and the PHANGS collaboration},
journal= {arXiv preprint arXiv:2510.11778},
year = {2026}
}
Comments
16 (+10) pages, 14 (+7) figures, 1 (+7) tables, accepted for publication in A&A, full catalogue available via CDS