A Database of 2MASS Near-Infrared Colors of Magellanic Cloud Star Clusters

Abstract

The (rest-frame) near-IR domain contains important stellar population diagnostics and is often used to estimate masses of galaxies at low as well as high redshifts. However, many stellar population models are still relatively poorly calibrated in this part of the spectrum. To allow an improvement of this calibration we present a new database of integrated near-infrared JHKs magnitudes for 75 star clusters in the Magellanic Clouds, using the 2-Micron All-Sky Survey (2MASS). The majority of the clusters in our sample have robust age and metallicity estimates from color-magnitude diagrams available in the literature, and populate a range of ages from 10 Myr to 15 Gyr and a range in [Fe/H] from -2.17 to +0.01 dex. A comparison with matched star clusters in the 2MASS Extended Source Catalog (XSC) reveals that the XSC only provides a good fit to the unresolved component of the cluster stellar population. We also compare our results with the often-cited single-channel JHK photometry of Persson and collaborators, and find significant differences, especially for their 30"-diameter apertures up to ~2.5 mag in the K-band, more than 1 mag in J-K, and up to 0.5 mag in H-K. Using simulations to center apertures based on maximum light throughput (as performed by Persson et al, we show that these differences can be attributed to near-IR-bright cluster stars (e.g., Carbon stars) located away from the true center of the star clusters. The wide age and metallicity coverage of our integrated JHKs photometry sample constitutes a fundamental dataset for testing population synthesis model predictions, and for direct comparison with near-IR observations of distant stellar populations.