A resolved study of the inner regions of nearby galaxies with an excess of young massive stars: missing link in the AGN–starburst connection?

Guinevere Kauffmann*, Iker Millán-Irigoyen, Paul Crowther, Claudia Maraston

*Corresponding author for this work

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Abstract

We have selected galaxies with very high levels of H α emission (EQW(H α) >700 Å.) in their central regions from the final data release of the MaNGA survey. Our study focuses on 14 very well-resolved nearby galaxies with stellar masses in the range 9.5 < log M/(M☉) < 11.5. We investigate a variety of procedures for selecting galaxy regions that are likely to harbour excess populations of young massive stars, finding that selection in the 2D space of extinction-corrected H α EQW and [S III]/[S II] line ratio produces the best results. By comparing stacked spectra covering these regions with stacked spectra covering normal starburst regions with 100 Å<EQW(H α) <200 Å, we obtain the following main results: (1) Clear signatures of excess Wolf–Rayet stars are found in half of the H α excess regions, (2) galaxy regions containing excess Wolf–Rayet stars are more often associated with the presence of high-ionization emission lines characteristic of accreting black holes. Excess [Ne III] is detected in 4 out of 8 of the WR regions and there are tentative [Fe X] detections in 2 galaxies. (3) Regions of the galaxy with excess Wolf–Rayet stars are located where the interstellar medium has larger ionized gas turbulent velocities and higher neutral gas overdensities. We make a first attempt to constrain changes in the high-mass end of the stellar initial mass function (IMF) using the HR-pyPopStar evolutionary population synthesis models that include high-wavelength-resolution theoretical atmosphere libraries for Wolf–Rayet stars.

Original languageEnglish
Pages (from-to)150-170
Number of pages21
JournalMonthly Notices of the Royal Astronomical Society
Volume527
Issue number1
Early online date12 Oct 2023
DOIs
Publication statusPublished - 1 Jan 2024

Keywords

  • active
  • bulges-galaxies
  • galaxies
  • nuclei-galaxies
  • star formation-galaxies
  • stellar content-stars
  • Wolf–Rayet-galaxies

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