2024/02/20 by V. M. A. Gómez-González, Gómez-González, V. M. A., Y. D. Mayya +15 · 1 citation
Chemistry · Earth and Planetary Sciences · Physics and Astronomy · #Astrophysics and Star Formation Studies #Astrophysics of Galaxies (astro-ph.GA) #Atmospheric Ozone and Climate #FOS: Physical sciences #Molecular Spectroscopy and Structure
paper · pdf · doi:10.48550/arxiv.2402.13230
openalex publication_date 2024/02/20 · openalex created_date 2024/02/22 · openalex updated_date 2026/08/01
We present the analysis of archival Very Large Telescope (VLT) Multi-Unit Spectroscopic Explorer (MUSE) observations of 179 HII regions in the star-forming double-ring collisional galaxy AM 0644-741 at 98.6 Mpc. We determined ionic abundances of He, N, O and Fe using the direct method for the brightest H II region (ID 39); we report log\rm((N)/(O))=-1.3±0.2 and 12+log\rm((O)/(H))=8.9±0.2. We also find the so-called `blue-bump', broad He II λ4686, in the spectrum of this knot of massive star-formation; its luminosity being consistent with the presence of ∼430 Wolf-Rayet (WR) stars of the Nitrogen late-type. We determined the O abundances for 137 HII regions using the strong-line method; we report a median value of 12+log\rm((O)/(H))=8.5±0.8. The location of three objects, including the WR complex, coincide with that of an Ultra Luminous X-ray source. Nebular He II is not detected in any H II region. We investigate the physical mechanisms responsible for the observed spectral lines using appropriate diagnostic diagrams and ionization models. We find that the H II regions are being photoionized by star clusters with ages ∼2.5-20 Myr and ionization potential -3.5<log⟨ U⟩<-3.0. In these diagrams, a binary population is needed to reproduce the observables considered in this work.