The PHANGS-MUSE/HST-H <i>α</i> nebulae catalogue

We present the PHANGS-MUSE/HST-H α nebulae catalogue, comprising 5177 spatially resolved nebulae across 19 nearby star-forming galaxies ( D &lt; 20 Mpc), based on high-resolution H α imaging from HST, homogenised to a fixed (10 pc) physical resolution and sensitivity. Combined with MUSE integral field spectroscopy, this enables robust classification of 4882 H II regions and the separation of planetary nebulae and supernova remnants. We derive electron densities for 2544 H II regions using [S II ] diagnostics and adopt direct or representative electron temperatures for consistent physical characterisation. Nebular sizes are measured using circularised radii and intensity-weighted second moments, yielding a median radius of approximately 20 pc and extending down to (sub-)parsec (deconvolved) radii. A structural complexity score is introduced via hierarchical segmentation to trace substructure, highlighting that around a third of the regions are H II complexes containing several individual clusters and bubbles, with an increased fraction of these regions in galactic centres. A luminosity–size relation, calibrated using the resolved HST sample, is applied to 30 790 MUSE nebulae, allowing the recovery of nebular sizes down to ~1 pc and providing statistical completeness beyond the HST detection limit. Comparisons with classical Strömgren radii indicate that observed sizes are systematically larger, corresponding to typical volume filling factors with a median of ϵ ~ 0.22 (10th–90th percentile 0.06–0.78), with larger regions exhibiting progressively lower values. We associate 3349 H II regions with stellar populations from the PHANGS-HST association catalogue, finding median ages of ~3 Myr and typical stellar masses of around 10 4 –10 5 M ⊙ , supporting the link between ionised nebular and young stellar populations. We also assess the impact of diffuse ionised gas on emission-line diagnostics and after removing confirmed supernova remnants, find no strong variation in line ratios with nebular resolution, indicating minimal systematic bias in the MUSE catalogue. This dataset establishes a detailed, spatially resolved connection between nebular structure and ionising sources, and provides a benchmark for future studies of feedback, DIG contributions, and star formation regulation in the ISM, especially in combination with matched high-resolution observations. The full catalogue is made publicly available in machine-readable format.

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Journal
Astronomy and Astrophysics
Published
2025-10-28
DOI
https://doi.org/10.1051/0004-6361/202555751
Citations
2
Primary Topic
Galaxies: Formation, Evolution, Phenomena
Type
article
Field-Weighted Citation Impact
2.31

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article

The PHANGS-MUSE/HST-H α nebulae catalogue

Kiana F. Henny, Justus Neumann, David A. Thilker, K. Kreckel et al.
2 citations
Astronomy and Astrophysics
Galaxies: Formation, Evolution, Phenomena
2.31
article

The PHANGS-MUSE/HST-H α nebulae catalogue

Kiana F. Henny, Justus Neumann, David A. Thilker, K. Kreckel, M. Boquien, Debosmita Pathak, Sharon E. Meidt, Aida Wofford, Francesco Belfiore, J.C. Lee, Vale González Lobos, S.C.O. Glover, B. Groves, Éric Emsellem, J. Eduardo Méndez-Delgado, Miguel Querejeta, Daniel Maschmann, Hao He, Ashley T. Barnes, Fabian Scheuermann, Thomas G. Williams, Sumit K. Sarbadhicary, Tony D. Weinbeck, Kirsten L. Larson, Enrico Congiu, Bradley C. Whitmore, A. Amiri, Adam K. Leroy, E. Rosolowsky, Fu-Heng Liang, Rupali Chandar, Leonardo Úbeda, Rebecca McClain, Hsi-An Pan, Daniel A. Dale, Oleg V. Egorov, R. Indebetouw, Zein Bazzi, Jing Li, K. Grasha
article en
2 citations

Abstract

We present the PHANGS-MUSE/HST-H α nebulae catalogue, comprising 5177 spatially resolved nebulae across 19 nearby star-forming galaxies ( D &lt; 20 Mpc), based on high-resolution H α imaging from HST, homogenised to a fixed (10 pc) physical resolution and sensitivity. Combined with MUSE integral field spectroscopy, this enables robust classification of 4882 H II regions and the separation of planetary nebulae and supernova remnants. We derive electron densities for 2544 H II regions using [S II ] diagnostics and adopt direct or representative electron temperatures for consistent physical characterisation. Nebular sizes are measured using circularised radii and intensity-weighted second moments, yielding a median radius of approximately 20 pc and extending down to (sub-)parsec (deconvolved) radii. A structural complexity score is introduced via hierarchical segmentation to trace substructure, highlighting that around a third of the regions are H II complexes containing several individual clusters and bubbles, with an increased fraction of these regions in galactic centres. A luminosity–size relation, calibrated using the resolved HST sample, is applied to 30 790 MUSE nebulae, allowing the recovery of nebular sizes down to ~1 pc and providing statistical completeness beyond the HST detection limit. Comparisons with classical Strömgren radii indicate that observed sizes are systematically larger, corresponding to typical volume filling factors with a median of ϵ ~ 0.22 (10th–90th percentile 0.06–0.78), with larger regions exhibiting progressively lower values. We associate 3349 H II regions with stellar populations from the PHANGS-HST association catalogue, finding median ages of ~3 Myr and typical stellar masses of around 10 4 –10 5 M ⊙ , supporting the link between ionised nebular and young stellar populations. We also assess the impact of diffuse ionised gas on emission-line diagnostics and after removing confirmed supernova remnants, find no strong variation in line ratios with nebular resolution, indicating minimal systematic bias in the MUSE catalogue. This dataset establishes a detailed, spatially resolved connection between nebular structure and ionising sources, and provides a benchmark for future studies of feedback, DIG contributions, and star formation regulation in the ISM, especially in combination with matched high-resolution observations. The full catalogue is made publicly available in machine-readable format.

Astronomy and AstrophysicsVol. 706
Tamkang University (TW), Australian National University (AU), University of Wyoming (US), Space Telescope Science Institute (US), University of Bonn (DE), University of Arizona (US), Johns Hopkins University (US), University of Alberta (CA), The University of Western Australia (AU), Université Côte d'Azur (FR), Heidelberg University (DE), National Radio Astronomy Observatory (US), Arcetri Astrophysical Observatory (IT), Laboratoire AstroParticule et Cosmologie (FR), Ghent University (BE), University of Oxford (GB), Max Planck Institute for Astronomy (DE), Gemini South Observatory (CL), Observatoire de la Côte d’Azur (FR), European Southern Observatory (CL), NSF NOIRLab (US), Spanish National Observatory (ES), International Centre for Radio Astronomy Research (AU), University of Virginia (US), The Ohio State University (US), University of Arkansas at Fayetteville (US), Universidad Nacional Autónoma de México (MX), University of Toledo (US)
National Aeronautics and Space Administration, Space Telescope Science Institute, Australian Government, Deutsche Forschungsgemeinschaft, Agence Nationale de la Recherche, European Southern Observatory, Agencia Nacional de Investigación y Desarrollo
Openalex Percentile: Top 10%
Galaxies: Formation, Evolution, Phenomena
2.31
DOIOpen Access PDFOpenAlex
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