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Properties of star clusters - II. Scaleheight evolution of clusters

Buckner, A.S.M, Froebrich, Dirk (2014) Properties of star clusters - II. Scaleheight evolution of clusters. Monthly Notices of the Royal Astronomical Society, 444 (1). pp. 290-302. ISSN 0035-8711. (doi:10.1093/mnras/stu1440) (KAR id:49548)

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Until now, it has been impossible to observationally measure how star cluster scaleheight evolves beyond 1 Gyr as only small samples have been available. Here, we establish a novel method to determine the scaleheight of a cluster sample using modelled distributions and Kolmogorov-Smirnov tests. This allows us to determine the scaleheight with a 25 per cent accuracy for samples of 38 clusters or more. We apply our method to investigate the temporal evolution of cluster scaleheight, using homogeneously selected sub-samples of Kharchenko et al. (MWSC), Dias et al. (DAML02), WEBDA, and Froebrich et al. (FSR). We identify a linear relationship between scaleheight and log(age/yr) of clusters, considerably different from field stars. The scaleheight increases from about 40 pc at 1Myr to 75 pc at 1 Gyr,most likely due to internal evolution and external scattering events. After 1 Gyr, there is amarked change of the behaviour, with the scaleheight linearly increasing with log(age/yr) to about 550 pc at 3.5 Gyr. The most likely interpretation is that the surviving clusters are only observable because they have been scattered away from the mid-plane in their past. A detailed understanding of this observational evidence can only be achieved with numerical simulations of the evolution of cluster samples in the Galactic disc. Furthermore, we find a weak trend of an age-independent increase in scaleheight with Galactocentric distance. There are no significant temporal or spatial variations of the cluster distribution zero-point. We determine the Sun's vertical displacement from the Galactic plane as Z± = 18.5 ± 1.2 pc. ©2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Item Type: Article
DOI/Identification number: 10.1093/mnras/stu1440
Uncontrolled keywords: Centre for Astrophysics and Planetary Sciences, Evolution-Galaxy, Galaxy, General, General-galaxy, General-open clusters and associations, Star clusters, Structure-galaxies
Subjects: Q Science > QB Astronomy
Q Science > QB Astronomy > QB460 Astrophysics
Divisions: Divisions > Division of Natural Sciences > Physics and Astronomy
Depositing User: Giles Tarver
Date Deposited: 20 Jul 2015 08:50 UTC
Last Modified: 03 Sep 2021 14:00 UTC
Resource URI: (The current URI for this page, for reference purposes)
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