Juan Betancort Rijo, Francisco Jiménez Forteza
In the seminal works of Zeldovich (1968) and Peebles (1968), a procedure was outlined to obtain the equation of evolution of the hydrogen fraction without an explicit use of the radiative transfer equation. This procedure is based, explicitly or implicitly, on Sobolev (1960) escape probability and has extensively been used since then in developing refined approximations. Here we present a somewhat different derivation of that procedure that is both simple and formally exact, and use it to assess the implications of a number of effects. The most remarkable one is the fact that a photon that has escaped from the line 2p -> 1s can be absorbed, conjointly with another photon with the appropriate frequency, by the two photon line 1s -> 2s. This effect, which apparently has not been treated before, implies a maximum increment in the electronic fraction of roughly a 2 % at z around 1100 which is large enough to have non-trivial consequences on the inference of cosmological parameters from CMB maps.
View original:
http://arxiv.org/abs/1306.6915
No comments:
Post a Comment