The Arches Cluster: Evidence for a Truncated Mass Function?

We have analyzed high-resolution, adaptive optics HK observations of the Arches cluster obtained with NAOS-CONICA. With a spatial resolution of 84 mas, the cluster center is uniquely resolved. From these data, the present-day mass function (MF) of the Arches cluster is derived down to ~4 M☉. The integrated MF and the core and second-annulus MFs are consistent with a turnover at 6-7 M☉. This turnover indicates severe depletion of intermediate- and low-mass stars in the Arches cluster, possibly caused by its evolution in the Galactic center environment. The Arches MF represents the first resolved observation of a starburst cluster exhibiting a low-mass-truncated MF. This finding has severe implications for stellar population synthesis modeling of extragalactic starbursts, the derivation of integrated properties such as the total mass of star clusters in dense environments, the survival of low-mass remnants from starburst populations, and chemical enrichment during starburst phases.

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