Ks Band Luminosity Evolution of the Asymptotic Giant Branch Population Based on Star Clusters in the Large Magellanic Cloud

TL;DR

This study investigates how the Ks band luminosity of AGB stars in star clusters from the Large Magellanic Cloud evolves with age, revealing a peak at around log(age) 8.5 and discussing implications for galaxy evolution.

Contribution

It provides empirical measurements of AGB luminosity fractions across a range of cluster ages and compares these with stellar population models, enhancing understanding of AGB evolution.

Findings

AGB luminosity fraction peaks at log(age) ~ 8.5

Large scatter in AGB luminosity due to stochastic effects

Models reproduce maximum AGB luminosity fraction at specific ages

Abstract

We present a study of Ks band luminosity evolution of the asymptotic giant branch (AGB) population in simple stellar systems using star clusters in the Large Magellanic Cloud (LMC). We determine physical parameters of LMC star clusters including center coordinates, radii, and foreground reddenings. Ages of 83 star clusters are derived from isochrone fitting with the Padova models, and those of 19 star clusters are taken from the literature. The AGB stars in 102 star clusters with log(age) = 7.3 - 9.5 are selected using near-infrared color magnitude diagrams based on 2MASS photometry. Then we obtain the Ks band luminosity fraction of AGB stars in these star clusters as a function of ages. The Ks band luminosity fraction of AGB stars increases, on average, as age increases from log(age) ~ 8.0, reaching a maximum at log(age) ~ 8.5, and it decreases thereafter. There is a large scatter in the AGB luminosity fraction for given ages, which is mainly due to stochastic effects. We discuss this result in comparison with five simple stellar population models. The maximum Ks band AGB luminosity fraction for bright clusters is reproduced by the models that expect the value of 0.7 - 0.8 at log(age) = 8.5 - 8.7. We discuss the implication of our results with regard to the study of size and mass evolution of galaxies.