A Young Super Star Cluster in the Nuclear Region of Ngc 253

We present observations of a massive star cluster near the nuclear region of the nearby starburst galaxy NGC 253. The peak of near-infrared emission, which is spatially separated by 4 from the kinematic center of the galaxy, is coincident with a super star cluster whose properties we examine with low-resolution (R ∼ 1,200) infrared CTIO spectroscopy and optical/near-infrared HST imaging. Extinction, measured from [Fe II] lines, is estimated at AV = 17.7±2.6. The age of the cluster is estimated at 5.7 Myr, based on Brγ equivalent width for an instantaneous burst using Starburst99 modeling. However, a complex star formation history is inferred from the presence of both recombination emission and photospheric CO absorption. The ionizing photon flux has a lower limit of 7.3±2.5 × 1053 s−1, corrected for extinction. Assuming a Kroupa IMF, we estimate a cluster mass of ∼ 1.4+0.4 −0.5 × 10 7 M⊙. We observe a strong Wolf-Rayet signature at 2.06 μm and report a weak feature at 2.19 μm which may be due to a massive stellar population, consistent with the derived mass and age of this cluster. Subject headings: galaxies: star clusters — galaxies: individual (NGC 253)