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An analysis of the distribution of globular clusters with postcollapse cores in the Galaxy

Chernoff, David F. and Djorgovski, S. (1989) An analysis of the distribution of globular clusters with postcollapse cores in the Galaxy. Astrophysical Journal, 339 . pp. 904-918. ISSN 0004-637X. doi:10.1086/167344.

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We present a new compilation of structural parameters for Galactic globular clusters, based on the data from the complete survey published by Djorgovski, King, and collaborators in 1984, 1986, and 1987 and the literature. We find that the distribution of the post-core-collapsed (PCC) clusters is much more concentrated about the Galactic center than the distribution of the King model (KM) clusters. Within the KM family, a similar trend exists: centrally condensed KM clusters are found, on average, at smaller galactocentric radii. To deal with the problem of Galactic obscuration, we used a distance-independent analysis, similar to one developed and published by Frenk and White in 1982. We analyzed the shapes of the KM and PCC cluster systems; they are each consistent with a symmetrical distribution of the clusters about the Galactic center. At fixed distance from the center, the clusters at smaller heights above the plane (and thus the less inclined orbits) are marginally more concentrated. The data indicate that the more concentrated KM clusters tend to have higher luminosities. On the other hand, the PCC clusters are less luminous than the highest concentration KM clusters. The PCC clusters show signs of tidal distortions in their envelopes: their major axes tend to point toward the Galactic center; the KM clusters show no such effect. There is a very slight difference in the average metallicities of the two families, in the sense that PCC clusters have slightly lower metal abundances, but there is no significant trend with the concentration within the KM family. The fact that some internal properties of clusters correlate well with global variables, such as the galactocentric radius, suggests that some external effects are important in cluster evolution. These include the average cluster density, set by the mean tidal field of the Galaxy, and, perhaps, the strength of tidal shocks.

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Djorgovski, S.0000-0002-0603-3087
Additional Information:© 1989 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1988 May 6; accepted 1988 September 20. We are very thankful to the staff of Cerro Tololo Interamerican Observatory for their help in obtaining the data used here. The Berkeley globular clusters survey was conducted in collaboration with Ivan R. King, who generously allowed us to use the data for this work and provided us with much good advice and many stimulating discussions. We also thank Abe Oren, Carl Vuosalo, and Howard Penner for their help in data reductions. We acknowledge helpful conversations with Piet Hut, Gerry Quinlan, Ira Wasserman, and Martin Weinberg. D. C. acknowledges support by NSF grant no. AST-84-15162 and AST-86-57467 at Cornell University. S. D. wishes to acknowledge partial support from Harvard University and California Institute of Technology.
Funding AgencyGrant Number
NSFAST 84-15162
NSFAST 86-57467
Harvard UniversityUNSPECIFIED
Subject Keywords:clusters: globular - galaxies: The Galaxy - galaxies: structure - stars: stellar dynamics
Record Number:CaltechAUTHORS:20190807-081605918
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97690
Deposited By: Tony Diaz
Deposited On:07 Aug 2019 16:20
Last Modified:16 Nov 2021 17:33

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