2021/11/17 by Francesco Santoro, Kathryn Kreckel, Francesco Belfiore +34
Chemistry · Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Galaxy #Luminosity #Luminosity function #Physics #Scientific Research and Discoveries #Spectroscopy and Laser Applications #Spiral (railway) #Spiral galaxy #Star formation #Stars #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · open access · doi:10.1051/0004-6361/202141907
published in Astronomy and Astrophysics 658, A188 (EDP Sciences) · Accepted in A&A. Main text: 19 pages, 11 Figures, 4 Tables. Catalog including 23301 HII regions will be available in electronic form at the CDS upon official publication
arxiv created 2021/11/17 · openalex publication_date 2021/11/30 · arxiv updated 2022/03/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
We use an unprecedented sample of about 23,000 HII regions detected at an average physical resolution of 67pc in the PHANGS-MUSE sample to study the extragalactic HII region Ha luminosity function (LF). Our observations probe the star-forming disk of 19 nearby spiral galaxies with low inclination and located close to the star formation main sequence at z=0. The mean LF slope α in our sample is =1.73 with a σ of 0.15. We find that α decreases with the galaxy's star formation rate surface density and argue that this is driven by an enhanced clustering of young stars at high gas surface densities. Looking at the HII regions within single galaxies we find that no significant variations occur between the LF of the inner and outer part of the star-forming disk, whereas the LF in the spiral arm areas is shallower than in the inter-arm areas for six out of the 13 galaxies with clearly visible spiral arms. We attribute these variations to the spiral arms increasing the molecular clouds arm--inter-arm mass contrast and find suggestive evidence that they are more evident for galaxies with stronger spiral arms. Furthermore, we find systematic variations in α between samples of HII regions with high and low ionization parameter q and argue that they are driven by the aging of HII regions.