Stellar Population near NGC 2021: Procession of Star Formation in the South Rim of Supergiant Shell LMC 4

TL;DR

This study investigates the star formation history near NGC 2021 in the Large Magellanic Cloud, revealing a radial progression of massive star formation and estimating supernova energy contributions to the supergiant shell LMC 4.

Contribution

It introduces a methodology to analyze stellar populations and star formation history using ground-based survey data in the LMC, focusing on NGC 2021 and its surroundings.

Findings

Radial procession of massive star formation observed.

Approximately four supernovae occurred in NGC 2021.

Injected at least 4×10^{51} ergs of energy into LMC 4.

Abstract

Supergiant shells (SGSs) are the largest interstellar structures where heated and enriched gas flows into the host galaxy's halo. The SGSs in the Large Magellanic Cloud (LMC) are so close that their stars can be resolved with ground-based telescopes to allow studies of star formation history. Aiming to study the star formation history and energy budget of LMC 4, we have conducted a pilot study of the cluster NGC 2021 and the OB associations in its vicinity near the south rim of LMC 4. We use the Magellanic Cloud Photometric Survey data of the LMC to establish a methodology to examine the stellar population and assess the massive star formation history. We find a radial procession of massive star formation from the northwest part of the OB association LH79 through NGC 2021 to the OB association LH78 in the south. Using the stellar content of NGC 2021 and the assumption of Salpeter's initial mass function, we estimate that $\sim$4 supernovae have occurred in NGC 2021, injecting at least $4\times10^{51}$ ergs of kinetic energy into the interior of LMC 4.