Near-Infrared spectroscopy of the super star cluster in NGC1705

TL;DR

This study uses adaptive optics integral field spectroscopy to analyze the near-infrared properties of the super star cluster NGC1750-1, constraining its size, stellar population, and age with high spatial resolution.

Contribution

It provides the first detailed near-infrared spectral analysis of NGC1750-1, estimating its size, age, and stellar composition using advanced observational techniques.

Findings

Cluster radius is less than approximately 2.85 pc.

Dominant stellar population is red supergiants of spectral type K4-5I.

Estimated age of the cluster is around 12 million years.

Abstract

We study the near-infrared properties of the super star cluster NGC1750-1 in order to constrain its spatial extent, its stellar population and its age. We use adaptive optics assisted integral field spectroscopy with SINFONI on the VLT. We estimate the spatial extent of the cluster and extract its K-band spectrum from which we constrain the age of the dominant stellar population. Our observations have an angular resolution of about 0.11", providing an upper limit on the cluster radius of 2.85+/-0.50 pc depending on the assumed distance. The K-band spectrum is dominated by strong CO absorption bandheads typical of red supergiants. Its spectral type is equivalent to a K4-5I star. Using evolutionary tracks from the Geneva and Utrecht groups, we determine an age of 12+/-6 Myr. The large uncertainty is rooted in the large difference between the Geneva and Utrecht tracks in the red supergiants regime. The absence of ionized gas lines in the K-band spectrum is consistent with the absence of O and/or Wolf-Rayet stars in the cluster, as expected for the estimated age.