Joint Analysis of near-infrared properties and surface brightness fluctuations of LMC star clusters

TL;DR

This study calibrates near-infrared surface brightness fluctuations of LMC star clusters to determine their properties and improve understanding of TP-AGB stars, aiding distance measurement and stellar population analysis.

Contribution

It provides a new calibration of the empirical s-parameter and demonstrates the use of NIR-SBFs to analyze TP-AGB stars in star clusters.

Findings

NIR-SBFs are highly sensitive to TP-AGB stars.

The study offers a consistent method to estimate cluster ages and metallicities.

Calibration of the s-parameter improves stellar population models.

Abstract

Surface brightness fluctuations have been proved to be a very powerful technique to determine the distance and characterize the stellar content in extragalactic systems. Nevertheless, before facing the problem of stellar content in distant galaxies, we need to calibrate the method onto nearby well-known systems. In this paper we analyze the properties at $J$ and $K_s$ bands of a sample of 19 star clusters in the Large Magellanic Cloud (LMC), for which accurate near-infrared (NIR) resolved star photometry, and integrated photometry are available. For the same sample, we derive the SBF measurements in $J$ and $K_s$-bands. We use the multi-purpose stellar population code \emph{SPoT (Stellar POpulations Tools)} to simulate the color-magnitude diagram, stellar counts, integrated magnitudes, colors, and surface brightness fluctuations of each cluster. The present procedure allows us to estimate the age and metallicity of the clusters in a consistent way, and provides a new calibration of the empirical $s$-parameter. We take advantage of the high sensitivity of NIR surface brightness fluctuations to thermally pulsing asymptotic (TP-AGB) stars to test different mass-loss rates affecting the evolution of such stars. We argue that NIR-SBFs can contribute to the disentangling of the observable properties of TP-AGB stars, especially in galaxies, where a large number of these stars are present.