Spectral Energy Distributions and Age Estimates of 39 Globular Clusters in M31

TL;DR

This study provides multicolor photometry and age estimates for 39 M31 globular clusters, revealing most are younger than 6 Gyr with a peak around 3 Gyr, enhancing understanding of their formation history.

Contribution

It offers new photometric data and age constraints for 39 M31 GCs, supplementing previous studies with UV and infrared data for improved age estimation.

Findings

Most clusters are younger than 6 Gyr

Age distribution peaks at approximately 3 Gyr

Presence of old GCs similar to Galactic counterparts

Abstract

This paper supplements Jiang et al. (2003), who studied 172 M31 globular clusters (GCs) and globular cluster candidates from Battistini et al. (1987) on the basis of integrated photometric measurements in the Beijing-Arizona-Taiwan-Connecticut (BATC) photometric system. Here, we present multicolor photometric CCD data (in the BATC system) for the remaining 39 M31 GCs and candidates. In addition, the ages of 35 GCs are constrained by comparing our accurate photometry with updated theoretical stellar synthesis models. We use photometric measurements from GALEX in the far- and near-ultraviolet and 2MASS infrared $JHK_s$ data, in combination with optical photometry. Except for two clusters, the ages of the other sample GCs are all older than 1 Gyr. Their age distribution shows that most sample clusters are younger than 6 Gyr, with a peak at ~3 Gyr, although the `usual' complement of well-known old GCs (i.e., GCs of similar age as the majority of the Galactic GCs) is present as well.