Relationship between the galactic matter distribution, cosmic-ray dynamics, and gamma-ray production

Journal Article · Mon Aug 01 04:00:00 EDT 1977 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/155411· OSTI ID:7214303

Kniffen, D A; Fichtel, C E; Thompson, D J

Theoretical considerations and analysis of the results of ..gamma..-ray astronomy suggest that the galactic cosmic rays are dynamically coupled to the interstellar matter through the magnetic fields; hence the the cosmic-ray density should be enhanced where the matter density is greatest on the scale of galactic arms. This concept has been explored in a galactic model using recent 21 cm radio observations of neutral hydrogen and 2.6 mm observations of carbon monoxide, which is considered to be a tracer of molecular hydrogen. The model assumes that (1) cosmic rays are galactic and not universal; (2) on the scale of galactic arms, the cosmic-ray column (surface) density is proportional to the total interstellar-gas column density; (3) the cosmic-ray scale height is significantly larger than the scale height of the matter; and (4) ours is a spiral galaxy characterized by an arm-to-interarm density ratio of about 3:1. The second assumption implies that the ..gamma..-ray emission is proportional to the square of the mass on the scale of galactic arms. The theoretical predictions for ..gamma..-rays produced by matter--cosmic-ray interactions in this model show a good correlation with the galactic ..gamma..-ray observations, not only in terms of the absolute intensities along the galactic plane but also in terms of the positions of specific galactic features near longitudes 315/sup 0/, 330/sup 0/--335/sup 0/, 340/sup 0/--345/sup 0/, 0/sup 0/, 25/sup 0/,and 35/sup 0/.

• Research Organization: NASA/Goddard Space Flight Center, Greenbelt, Maryland
• OSTI ID: 7214303
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 215:3; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BREMSSTRAHLUNG
COSMIC ELECTRONS
COSMIC GASES
COSMIC RADIATION
DISTRIBUTION
ELECTROMAGNETIC RADIATION
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
FLUIDS
GALAXIES
GAMMA RADIATION
GASES
INTERSTELLAR SPACE
IONIZING RADIATIONS
LEPTONS
MAGNETIC FIELDS
MILKY WAY
RADIATIONS
SPACE
SPATIAL DISTRIBUTION