On the Formation of Perseus OB1 at High Galactic Latitudes

TL;DR

This paper investigates the formation of the Per OB1 association at high galactic latitudes, proposing it was shaped by an expanding superbubble that expelled molecular gas and triggered star formation far from the galactic plane.

Contribution

It presents new evidence linking the kinematics and star formation regions of Per OB1 to a superbubble-driven formation scenario, supported by Hipparcos data and observations of young stars at high galactic latitudes.

Findings

Luminous members move away from the galactic plane with increasing velocity.

Star-forming regions are located 280-400 pc above the galactic plane.

Younger stars tend to be at higher galactic latitudes, indicating recent star formation episodes.

Abstract

The Per OB1 association, which contains the remarkable double cluster h and chi Per, is unusual in not having a giant molecular cloud in its vicinity. We show from Hipparcos data that the luminous members of this association exhibits 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 towards probable remnant molecular clouds associated with Per OB1. These star-forming regions lie well beyond the location of the luminous member stars at heights of 280-400 pc above the galactic plane, far higher than that previously found for embedded clusters. We argue that the observed motion of the luminous member stars is most naturally explained if many formed from molecular gas pushed and accelerated outwards by an expanding superbubble driven presumably by stellar winds and perhaps also supernova explosions. A large shell of atomic hydrogen gas and dust that lies just beyond the remnant molecular clouds, believed to be driven by just such a superbubble, may comprise the swept-up remains of the parental giant molecular cloud from which this association formed. In support of this picture, we find a week trend for the younger O star members to lie at higher galactic latitudes than the older supergiant members. The star-forming regions located at even larger heights above the galactic plane presumably correspond to more recent episodes of star formation at or near the periphery of this superbubble.