Large Scale Structure, Kinematics, and Temperature Distribution of the Orion Ridge

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Session 26 -- Molecular Cloud Structure and Energetics
Oral presentation, Wednesday, January 12, 10:15-11:45, Crystal Forum Room (Crystal City Marriott)

[26.01] Large Scale Structure, Kinematics, and Temperature Distribution of the Orion Ridge

J.J. Wiseman, P.T.P. Ho (CFA)

We present a high resolution VLA study of the 0.5 pc extended OMC-1 molecular ridge surrounding the Orion BN/KL core of high mass star formation. Molecular streamers based in the BN/KL core region have previously been reported in this region. To clarify the structure and kinematics of the region, we have used the VLA to observe with high (0.3 km s$^{-1}$) velocity resolution and high (9$''$) angular resolution the NH$_3$ (1,1) and (2,2) rotation-inversion lines over 20 adjacent fields covering a 3$'$ by 9$'$ region encompassing the Kleinman-Low (KL) nebula. We present a linear mosaic of these fields, which show an abundance of structural, kinematical, and temperature information. Techniques and challenges encountered while mosaicing the interferometric maps are discussed. We find evidence of extended clumpy filaments. The component fragments display velocity gradients in varying directions; some may be sites of young stars or collapsing cores which have not yet shed their angular momentum. We also find material with velocities differing by more than 2 km s$^{-1}$ present within small projected areas, complicating simple global rotation models for OMC-1. These bimodal velocity components appear to overlap in the BN/KL active core region, suggesting cloud collision as a possible triggering mechanism. We also present a temperature map of the ridge. There is evidence for large scale (0.5 pc) outflows originating from the KL core and extending along the filaments, with possible shock heating and interaction. We discuss the likelihood of instability and fragmentation along the filaments. These observations provide an interesting case study of the active interaction between a core of high mass star formation and its molecular cloud environment.

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