Bibcode
Rubiño-Martín, J. A.; Hernández-Monteagudo, C.; Sunyaev, R. A.
Bibliographical reference
Astronomy and Astrophysics, Volume 438, Issue 2, August I 2005, pp.461-473
Advertised on:
8
2005
Journal
Citations
21
Refereed citations
18
Description
We explore the imprint of the cosmological hydrogen recombination lines
on the power spectrum of the cosmic microwave background (CMB). In
particular, we focus on the three strongest lines for the Balmer,
Paschen and Brackett series of hydrogen. We expect changes in the
angular power spectrum due to these lines of about 0.3 μK for the
Hα line, being maximum at small angular scales (ℓ ≈ 870).
The morphology of the signal is very rich. It leads to relatively narrow
spectral features (Δ ν / ν ˜ 10-1), with
several regions in the power spectrum showing a characteristic change of
sign of the effect as we probe different redshifts or different
multipoles by measuring the power spectrum at different frequencies. It
also has a very peculiar dependence on the multipole scale, connected
with the details of the transfer function at the epoch of scattering. In
order to compute the optical depths for these transitions, we have
numerically evolved the populations of the levels of the hydrogen atom
during recombination, simultaneously treating the evolution of helium.
For the hydrogen atom, we follow each angular momentum state separately,
up to the level n=10. Foregrounds and other frequency dependent
contaminants such as Rayleigh scattering may be a important limitation
for these measurements, although the peculiar frequency and angular
dependences of the effect that we are discussing might permit us to
separate it. Detection of this signal using future narrow-band spectral
observations can give information about the details of how the cosmic
recombination proceeds, and how Silk damping operates during
recombination.