CO Observations of the -Orionis Ring

Distribution of Young Stars

The distribution of low- to intermediate-mass young stars can be traced by excess H-emission, which is a characteristic of T Tauri stars. We plot the catalogue members from the H point source survey of Duerr et al. (1982), along with the OB-stars (Fig 3).

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Figure 3: H-emitting stars (crosses) and OB stars (triangles) in the -Ori region.

This recent (< 3 Myrs) star formation has occurred almost exclusively in a thin band running though the northern part of the Ring, between the B35 and B30 complexes. This presumably traces the position of the `fossil molecular cloud' (Duerr at al. 1982), prior to disruption by the HII region. The position of the star formation band is roughly coincident with HI (Hartmann 1995) and diffuse H filaments. Given the identification of these filaments with the Orion-Eridanus Bubble (Brown et al. 1995), this is evidence for star formation triggered by some event causing compression of the primordial -Ori GMC along its southern edge.

á© Copyright Astronomical Society of Australia 1997