Revisiting newly Large Magellanic Cloud age gap star clusters

TL;DR

This study re-examines star clusters in the Large Magellanic Cloud's age gap using deep color-magnitude diagrams, finding that many candidates are likely field star fluctuations rather than true clusters.

Contribution

It provides a detailed analysis of 17 candidate clusters with improved field star cleaning, challenging previous identifications of clusters in the LMC's age gap.

Findings

Many candidate clusters are likely field star density fluctuations.

Deeper photometry is needed for definitive cluster confirmation.

The study refines the understanding of the LMC's star cluster population.

Abstract

Recently, a noticeable number of new star clusters was identified in the outskirts of the Large Magellanic Cloud (LMC) populating the so-called star cluster age gap, a space of time (~ 4-12 Gyr) where the only known star cluster is up-to-date ESO121-SC\,03. We used Survey of the Magellanic Stellar History (SMASH) DR2 data sets, as well as those employed to identify these star cluster candidates, to produce relatively deep color-magnitude diagrams (CMDs) of 17 out of 20 discovered age gap star clusters with the aim of investigating them in detail. Our analysis relies on a thorough CMD cleaning procedure of the field star contamination, which presents variations in its stellar density and astrophysical properties, such as luminosity and effective temperature, around the star cluster fields. We built star cluster CMDs from stars with membership probabilities assigned from the cleaning procedure. These CMDs and their respective spatial distribution maps favor the existence of LMC star field density fluctuations rather than age gap star clusters, although a definitive assessment on them will be possible from further deeper photometry.