Astron. Astrophys. Suppl. Ser.
Volume 146, Number 1, October I 2000
|57 - 72
|15 October 2000
Morphologies and ages of star cluster pairs and multiplets in the Small Magellanic Cloud *
Instituto de Fisica-UFRGS, CP. 15051, CEP 91501-970 POA - RS, Brazil
Send offprint request to: M.R. de Oliveira, e-mail: email@example.com
Accepted: 21 June 2000
An isophotal atlas of 75 star cluster pairs and multiplets in the Small Magellanic Cloud is presented, comprising 176 objects. They are concentrated in the SMC main body. The isophotal contours were made from Digitized Sky Survey* images and showed relevant structural features possibly related to interactions in about 25% of the sample. Previous N-body simulations indicate that such shapes could be due to tidal tails, bridges or common envelopes. The diameter ratio between the members of a pair is preferentially in the range , with a peak at 1. The projected separation is in the range ≈ pc with a pronounced peak at ≈ 13 pc. For 91 objects it was possible to derive ages from Colour-Magnitude Diagrams using the OGLE-II photometric survey. The cluster multiplets in general occur in OB stellar associations and/or HII region complexes. This indicates a common origin and suggests that multiplets coalesce into pairs or single clusters in a short time scale. Pairs in the SMC appear to be mostly coeval and consequently captures are a rare phenomenon. We find evidence that star cluster pairs and multiplets may have had an important role in the dynamical history of clusters presently seen as large single objects.
Key words: Magellanic Clouds / star clusters
The images in this study are based on photographic data obtained using the UK Schmidt Telescope, which was operated by the Royal Observatory Edinburgh, with funding from the UK Science and Engineering Research Council, until 1988 June, and thereafter by the Anglo-Australian Observatory. Original plate material is copyright by the Royal Observatory Edinburgh and the Anglo-Australian Observatory. The plates were processed into the present compressed digital form with their permission. The Digitized Sky Survey was produced at the Space Telescope Science Institute under US Government grant NAG W-2166.
© European Southern Observatory (ESO), 2000