Decaying Neutrinos, the Metagalactic Radiation Field, and the Ionization of Nitrogen in the Interstellar Medium

Details Decaying Neutrinos, the Metagalactic Radiation Field, and the Ionization of Nitrogen in the Interstellar Medium Decaying Neutrinos, the Metagalactic Radiation Field, and the Ionization of Nitrogen in the Interstellar Medium

Aug 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...448..667s&link_type=abstract

Astrophysical Journal v.448, p.667

Astronomy and Astrophysics

Astronomy

21

Cosmology: Diffuse Radiation, Cosmology: Dark Matter, Elementary Particles, Ultraviolet: Ism

Scientific paper

The decaying neutrino theory for the ionization of the interstellar medium is reevaluated in the light of recent observational results. Estimates of the isotropic component of the far-UV background at 1500 Å are now in agreement with this theory. A new constraint on the metagalactic flux F of Lyman continuum photons at zero redshift, resulting from Hα observations of the intergalactic H I cloud 1225+01, leads to a new constraint on the energy Eγ of the decay photons, namely, Eγ = 13.7±0 1 eV and on the mass mv of the decaying neutrinos, namely, mv = 27.4±0.2 eV. We still find Ω ˜ 1 for the cosmological density parameter. If Ω = 1 exactly, then the Hubble constant H0 = 54±0.5 km s-1 Mpc-1.
The new constraint on F is still compatible with the hypothesis that decay photons are mainly responsible for the ionization of hydrogen in Lyα clouds and the intergalactic medium at both small and large redshifts. However, decay photons can no longer ionize nitrogen, so the origin of the widespread distribution of N II observed in the Galaxy and in NGC 891 must be reconsidered. It is shown that in the presence of the proposed galactic flux Fg of decay photons, an additional flux of conventional ionizing photons of only 1% of Fg would suffice to account for the observed distribution of N II.

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