IR Surface Brightness Fluctuations of Magellanic Star Clusters

We present surface brightness fluctuations (SBFs) in the near–IR for 191 Magellanic star clusters available in the Second Incremental and All Sky Data releases of the Two Micron All Sky Survey (2MASS), and compare them with SBFs of Fornax Cluster galaxies and with predictions from stellar population models as well. We also construct color–magnitude diagrams (CMDs) for these clusters using the 2MASS Point Source Catalog (PSC). Our goals are twofold. First, to provide an empirical calibration of near–IR SBFs, given that existing stellar population synthesis models are particularly discrepant in the near–IR. Second, whereas most previous SBF studies have focused on old, metal rich populations, this is the first application to a system with such a wide range of ages (∼ 106 to more than 1010 yr, i.e., 4 orders of magnitude), at the same time that the clusters have a very narrow range of metallicities (Z ∼ 0.0006 – 0.01, ie., 1 order of magnitude only). Since stellar population synthesis models predict a more complex sensitivity of SBFs to metallicity and age in the near–IR than in the optical, this analysis offers a unique way of disentangling the effects of age and metallicity. This research has made use of the NASA/ IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. E-mail address: [email protected] E-mail address: [email protected] E-mail address: [email protected]