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arXiv · 0909.4053

An HST/WFPC2 Survey of Bright Young Clusters in M31 III. Structural Parameters

P. Barmby·S. Perina·M. Bellazzini·J. G. Cohen·P. W. Hodge·J. P. Huchra·M. Kissler-Patig·T. H. Puzia·J. Strader
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Abstract

Surface brightness profiles for 23 M31 star clusters were measured using images from the Wide Field Planetary Camera 2 on the Hubble Space Telescope, and fit to two types of models to determine the clusters' structural properties. The clusters are primarily young (~10^8 yr) and massive (~10^4.5 solar masses), with median half-light radius 7 pc and dissolution times of a few Gyr. The properties of the M31 clusters are comparable to those of clusters of similar age in the Magellanic Clouds. Simulated star clusters are used to derive a conversion from statistical measures of cluster size to half-light radius so that the extragalactic clusters can be compared to young massive clusters in the Milky Way. All three sets of star clusters fall approximately on the same age-size relation. The young M31 clusters are expected to dissolve within a few Gyr and will not survive to become old, globular clusters. However, they do appear to follow the same fundamental plane relations as old clusters; if confirmed with velocity dispersion measurements, this would be a strong indication that the star cluster fundamental plane reflects universal cluster formation conditions.

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P. Barmby, S. Perina, M. Bellazzini, J. G. Cohen, P. W. Hodge, J. P. Huchra, M. Kissler-Patig, T. H. Puzia, J. Strader. 2009-09-22. An HST/WFPC2 Survey of Bright Young Clusters in M31 III. Structural Parameters. https://doi.org/10.1088/0004-6256%2F138%2F6%2F1667

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