Portal de Periódicos da CAPES

Stellar associations powering H ii regions – I. Defining an evolutionary sequence

2023; Oxford University Press; Volume: 522; Issue: 2 Linguagem: Inglês

10.1093/mnras/stad878

1365-2966

Fabian Scheuermann, Kathryn Kreckel, A. Barnes, Francesco Belfiore, Brent Groves, Stephen Hannon, Janice Lee, Rebecca Minsley, Erik Rosolowsky, Frank Bigiel, Guillermo A. Blanc, M. Boquien, Daniel A. Dale, Sinan Deger, Oleg V. Egorov, Éric Emsellem, Simon C. O. Glover, Kathryn Grasha, Hamid Hassani, Sarah Jeffreson, Ralf S. Klessen, J. M. Diederik Kruijssen, Kirsten L. Larson, Adam K. Leroy, Laura A. Lopez, Hsi-An Pan, P. Sánchez–Blázquez, Francesco Santoro, E. Schinnerer, David A. Thilker, Bradley C. Whitmore, Elizabeth J. Watkins, Thomas G. Williams,

Gamma-ray bursts and supernovae

ABSTRACT Connecting the gas in H ii regions to the underlying source of the ionizing radiation can help us constrain the physical processes of stellar feedback and how H ii regions evolve over time. With PHANGS–MUSE, we detect nearly 24 000 H ii regions across 19 galaxies and measure the physical properties of the ionized gas (e.g. metallicity, ionization parameter, and density). We use catalogues of multiscale stellar associations from PHANGS–HST to obtain constraints on the age of the ionizing sources. We construct a matched catalogue of 4177 H ii regions that are clearly linked to a single ionizing association. A weak anticorrelation is observed between the association ages and the $\mathrm{H}\, \alpha$ equivalent width $\mathrm{EW}(\mathrm{H}\, \alpha)$, the $\mathrm{H}\, \alpha/\mathrm{FUV}$ flux ratio, and the ionization parameter, log q. As all three are expected to decrease as the stellar population ages, this could indicate that we observe an evolutionary sequence. This interpretation is further supported by correlations between all three properties. Interpreting these as evolutionary tracers, we find younger nebulae to be more attenuated by dust and closer to giant molecular clouds, in line with recent models of feedback-regulated star formation. We also observe strong correlations with the local metallicity variations and all three proposed age tracers, suggestive of star formation preferentially occurring in locations of locally enhanced metallicity. Overall, $\mathrm{EW}(\mathrm{H}\, \alpha)$ and log q show the most consistent trends and appear to be most reliable tracers for the age of an H ii region.