OBSERVATIONAL EVIDENCE FOR TRIGGERED STAR FORMATION ON SCALES OF 1 TO 300 PC

We present evidence for triggered star formation on two dieren t spatial scales in the NGC 281 molecular cloud complex. This remarkable complex is situated 300 pc above the Galactic plane, and appears to be part of a 270 pc diameter ring of atomic and molecular clouds expanding at 22 km s 1 . We suggest that the ring has formed in a superbubble blowout driven by OB stars in the plane of the Galaxy. Within the cloud complex, combined optical, NIR, mm and cm data detailing the interaction of a young O star with neighboring molecular cores, provide evidence of triggered star formation inside the cloud complex on a few parsec scale. These data suggest that two modes of triggered star formation are operating in the NGC 281 complex|the initial supernovae triggered formation of the entire complex and, after the rst generation of O stars formed, the subsequent triggering of star formation by photoevaporation-driven molecular core compression.