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

TL;DR

This paper reports the discovery and detailed analysis of a massive, young super star cluster in the nuclear region of NGC 253, revealing its properties, age, mass, and stellar population characteristics through infrared and optical observations.

Contribution

It provides the first detailed characterization of a super star cluster in NGC 253's nuclear region, including its age, mass, and stellar content, using combined infrared and optical data.

Findings

Cluster age estimated at 5.7 Myr

Mass of approximately 1.4 x 10^7 solar masses

Presence of Wolf-Rayet stars indicating a massive stellar population

Abstract

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 [FeII] lines, is estimated at Av = 17.7 +/- 2.6. The age of the cluster is estimated at 5.7 Myr, based on Bry 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 x 10^53 inverse seconds, corrected for extinction. Assuming a Kroupa IMF, we estimate a cluster mass of 1.4 +/- 0.4 x 10^7 solar masses. We observe a strong Wolf-Rayet signature at 2.06 microns and report a weak feature at 2.19 microns which may be due to a massive stellar population, consistent with the derived mass and age of this cluster.