High Energy Gamma Ray Emission from the Interstellar Clouds in Orion
Session 99 -- Molecular Clouds and Star Formation
Oral presentation, Friday, January 14, 2:15-3:45, Salon VI Room (Crystal Gateway)

## [99.01] High Energy Gamma Ray Emission from the Interstellar Clouds in Orion

S.W. Digel (Harvard/GSFC), D.L. Bertsch, C.E. Fichtel, R.C. Hartman, S.D. Hunter,D.J. Thompson (NASA/GSFC), B.L. Dingus, J.A. Esposito, P. Sreekumar (USRA/GSFC), G. Kanbach, H.A. Mayer-Hasselwander, C. von Montigny (MPE), Y.C. Lin, P.F. Michelson, P.L. Nolan (Stanford), D.A. Kniffen (Hampden-Sydney), J.R. Mattox (CSC/GSFC), E.J. Schneid (Grumman)

The interstellar clouds in Orion, which comprise the nearest giant molecular cloud complex, are good subjects for study of the diffuse, high energy (E $\rm>$ 30 MeV) gamma ray emission that results from cosmic ray interactions with the interstellar medium. The large angular size of the Orion complex and the unprecedented sensitivity and resolution of the EGRET instrument on the Compton Gamma Ray Observatory permit the search for variations in the gamma ray production function and the $N({\rm H_2})$/$W_{\rm CO}$ ratio within the complex. Because of the recent and ongoing massive star formation in Orion, analysis of the gamma ray emission can be related to proposed mechanisms of cosmic ray production. We will present an analysis of the EGRET observations of the Orion complex obtained in the first two years of the operation of GRO, and a comparison with the findings from the study by Bloemen et al. (1984, A\&A 139, 37) using COS-B data.