Molecular hydrogen in the galaxy and galactic gamma rays

Journal Article · Wed Oct 01 04:00:00 EDT 1975 · Astrophys. J., v. 201, no. 1, pp. 90-97

DOI:https://doi.org/10.1086/153862· OSTI ID:4099028

Stecker, F W; Solomon, P M; Scoville, N Z; Ryter, C E

Recent surveys of 2.6-cm CO emission and 100-MeV $gamma$-radiation in the galactic plane reveal striking correlation suggesting that both emissions may be primarily proportional to the line-of-sight column density of H$sub 2$ in the inner Galaxy. Both the $gamma$-ray and CO data suggest a prominent ring or arm consisting of cool clouds of H$sub 2$ at a galactocentric distance of approx. 5 kpc with a mean total hydrogen density equivalent to approx.5 atoms cm$sup -3$. Estimates are made of column densities of H$sub 2$ at l/sup II/=0degree. The estimates at 0degree are compared with estimates from infrared and X-ray absorption measurements. These estimates are all consistent and indicate that H$sub 2$ is far more abundant than H i in the inner Galaxy and is the key to a more satisfactory explanation of the $gamma$-ray observations than previous suggestions. The importance of H$sub 2$ in understanding galactic $gamma$-ray observations is also reflected in the correlation of galactic latitude distribution of $gamma$-rays and dense dust clouds. The deduced cosmic-ray distribution inferred from the calculations is similar to that of galactic supernova remnants, suggesting a galactic origin for most cosmic rays. (AIP)

• Research Organization: Theoretical Studies Group, NASA Goddard Space Flight Center, Greenbelt
• Sponsoring Organization: USDOE
• NSA Number: NSA-33-018169
• OSTI ID: 4099028
• Journal Information: Astrophys. J., v. 201, no. 1, pp. 90-97, Journal Name: Astrophys. J., v. 201, no. 1, pp. 90-97; ISSN ASJOA
• Country of Publication: United States
• Language: English

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