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Paper: Dynamic Evidence of Triggered Star Formation
Volume: 387, Massive Star Formation: Observations Confront Theory
Page: 177
Authors: Lee, H.-T.; Lim, J.
Abstract: The Per OB1 association, which contains the remarkable double cluster h and χ Per, is unusual in that it is not associated with a giant molecular cloud. We demonstrate from Hipparcos data that the luminous early- and late-type members of this association exhibit a bulk motion away from the galactic plane, such that their average velocity increases with height above the galactic plane. We find HAeBe and T Tauri stars associated with structures reminiscent of remnant molecular clouds that we show to be likely associated with Per OB1. These star-forming regions are located 280–390 pc above the galactic plane, the highest thus far found for star clusters embedded in molecular clouds, beyond the locations of the luminous member stars. We point out that the large and massive atomic hydrogen gas and dust shell, which was suggested to be created by an expanding stellar-wind superbubble from the double cluster and OB stars in Per OB1, likely comprise (in part) the swept-up remains of the giant molecular cloud from which Per OB1 formed. We show that the observed motion of the member stars is most naturally explained if many stars formed from molecular gas and accelerated outwards by this expanding superbubble. Consistent with this idea, we find a trend (albeit of marginal significance) for the younger O stars to lie at higher galactic latitudes than the older supergiant member stars. The star-forming regions located at large heights above the galactic plane correspond to more recent episodes of star formation at or near the periphery of this superbubble.
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