Chemical abundances and ionizing mechanisms in the star-forming double-ring of AM 0644-741 using MUSE data
Gómez-González, V. M. A.; Mayya, Y. D.; Zaragoza-Cardiel, J.; Bruzual, G.; Charlot, S.; Ramos-Larios, G.; Oskinova, L. M.; Sander, A. A. C.; Serantes, S. Reyero
We present the analysis of archival Very Large Telescope Multi-Unit Spectroscopic Explorer observations of 179 H II 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(N/O)=−1.3±0.2 and 12+log(O/H)=8.9±0.2. We also find the so-called 'blue-bump', broad He II 4686, 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 H II regions using the strong-line method; we report a median value of 12+log(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.
Preprint (mauricio+mayya+2024.pdf, 2.6MB)This paper in ADS