Molecular hydrogen in the galaxy and galactic gamma rays
Technical Report
·
OSTI ID:4199495
Recent surveys of 2.6 mm CO emission and 100 MeV gamma-radiation in the galactic plane reveal a striking correlation suggesting that both emissions may be primarily proportional to the line-of-sight column density of H2 in the inner galaxy. Both the gamma ray and CO data suggest a prominent ring or arm consisting of cool clouds of H2 at a galactocentric distance of approximately 5 kpc with a mean density of approximately 4 atoms/cu cm. The importance of H2 in understanding galactic gamma ray observations is also reflected in the correlation of galactic latitude distribution of gamma rays and dense dust clouds. A detailed calculation of the gamma ray flux distribution in the 0 deg to 180 deg range using the CO data to obtain the average distribution of molecular clouds in the galaxy shows that most of the enhancement in the inner galaxy is due to pion- decay radiation and the 5 kpc ring plays a major role. Detailed agreement with the gamma ray data is obtained with the additional inclusion of contributions from bremsstrahlung and Compton radiation of secondary electrons and Compton radiation from the intense radiation field near the galactic center. (auth)
- Research Organization:
- National Aeronautics and Space Administration, Greenbelt, Md. (USA). Goddard Space Flight Center
- NSA Number:
- NSA-33-003828
- OSTI ID:
- 4199495
- Report Number(s):
- N--75-19119; NASA-TM-X--70839; X--602-75-24
- Country of Publication:
- United States
- Language:
- English
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