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R. F. Rees (Westfield State College and Yerkes Observatory), K. M. Cudworth (Yerkes Observatory, The University of Chicago)
A proper motion study of the globular cluster NGC 6397 (Rees et al., in preparation) found that the cluster passed through the Galactic disk less than 5 Myr ago. The three-dimensional space velocity of NGC 6397 from that study allows us to determine where it hit the disk. We have used various measurements of the absolute proper motion and radial velocity of the young open cluster NGC 6231 (often considered the core of the Sco OB1 association) from the literature to derive its three-dimensional space velocity and find that it would have been near NGC 6397's impact point at that time. Age determinations for NGC 6231 in the literature are consistent with its formation at the time of or soon after the NGC 6397 disk crossing. We propose that the disk passage of NGC 6397 may have triggered the formation of NGC 6231. If so, this would be the first observational evidence for the disk passage of globular clusters as a dynamical trigger of star formation, a mechanism proposed by Wallin et al. (1996, ApJ, 459, 555). This research has been partially supported by the NSF and the Westfield State College Faculty Continuing Scholarship Fund.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.