Chemical abundances and ionizing mechanisms in the star-forming double-ring of AM 0644-741 using MUSE data

V. M. A. Gómez-González; Y. D. Mayya; J. Zaragoza-Cardiel; G. Bruzual; S. Charlot; G. Ramos-Larios; L. M. Oskinova; A. A. C. Sander; S. Reyero Serantes

arXiv · 2402.13230

Chemical abundances and ionizing mechanisms in the star-forming double-ring of AM 0644-741 using MUSE data

V. M. A. Gómez-González·Y. D. Mayya·J. Zaragoza-Cardiel·G. Bruzual·S. Charlot·G. Ramos-Larios·L. M. Oskinova·A. A. C. Sander·S. Reyero Serantes

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Abstract

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 $\log\rm{(\frac{N}{O})}=-1.3\pm0.2$ and $12+\log\rm{(\frac{O}{H})}=8.9\pm0.2$. We also find the so-called `blue-bump', broad He II $\lambda4686$, in the spectrum of this knot of massive star-formation; its luminosity being consistent with the presence of $\sim430$ 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 $12+\log\rm{(\frac{O}{H})}=8.5\pm0.8$. 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 $\sim2.5-20$ Myr and ionization potential $-3.5<$$\log\langle U\rangle$$<-3.0$. In these diagrams, a binary population is needed to reproduce the observables considered in this work.

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V. M. A. Gómez-González, Y. D. Mayya, J. Zaragoza-Cardiel, G. Bruzual, S. Charlot, G. Ramos-Larios, L. M. Oskinova, A. A. C. Sander, S. Reyero Serantes. 2024-02-20. Chemical abundances and ionizing mechanisms in the star-forming double-ring of AM 0644-741 using MUSE data. https://arxiv.org/abs/2402.13230

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