Stellar Population and Energy Feedback in the Supergiant Shell LMC 1

Abstract

Supergiant shells (SGSs) are the largest interstellar structures in galaxies and inject hot enriched gas into galactic halos. We have studied SGS LMC 1 to determine quantitatively whether stellar energy feedback is adequate to power the formation of an SGS. The Gaia EDR3 photometric data of the OB association LH15 inside SGS LMC 1 are used to construct color–magnitude diagrams, and stellar evolutionary tracks and isochrones are used to assess stellar masses and ages. The observed present-day mass function is compared with the Salpter initial mass function to estimate the number of massive stars that have exploded as supernovae. Their total stellar wind mechanical energy and supernova explosion energy input amounts to (57 ± 12) × 10 ^51 erg. For the gas components of SGS LMC 1, ATCA+Parkes H i data are used to determine the total mass and kinetic energy in the H i shell, MCELS H α image is used to determine the ionized gas mass and kinetic energy, adopting the H i expansion velocity, and ROSAT X-ray observations are used to estimate the thermal energy in the SGS interior. The sum of the kinetic and thermal energies in the three layers is estimated to be (59 ± 5) × 10 ^51 erg. Thus, the stellar energy feedback from LH15 appears adequate to power the formation of SGS LMC 1. The radial age gradient in LH15 and the young stellar objects along the outer periphery indicate a progression of star formation, which might be a crucial factor for an SGS to grow to its large size.

Keywords

• Interstellar medium
• Large Magellanic Cloud
• Magellanic Clouds
• OB associations
• Superbubbles