Open AccessOn the interaction between cosmic rays and dark matter molecular clouds in the Milky Way – I. Basic considerations
Author(s) -
Sciama D. W.
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03072.x
Subject(s) - physics , cosmic ray , milky way , astrophysics , galaxy , galactic plane , astronomy , molecular cloud , dark matter , flux (metallurgy) , background radiation , radiation , nuclear physics , stars , materials science , metallurgy
We explore some basic observational consequences of assuming that the dark matter in the Milky Way consists mainly of molecular clouds, and that cosmic rays can penetrate these clouds. In a favoured model of the clouds, this penetration would have the following consequences, all of which agree with observation. (i) Cosmic ray nuclei would be fragmented when they enter a cloud, giving them a lifetime in the Galaxy of ∼10 15 s (for relativistic nuclei). (ii) Pionic γ ‐rays emitted by the clouds, after proton–proton (pp) collisions, would have a diffuse flux in the Galactic plane comparable to the flux from known sources for photon energies ≳1 GeV . (iii) The heat input into the clouds from cosmic rays would be re‐radiated mainly in the far‐infrared. The resulting radiation background agrees, in both intensity and spectrum in different directions, with a known excess in the far‐infrared background of the galaxy over emission by warm dust.