Issue |
A&A
Volume 485, Number 2, July II 2008
|
|
---|---|---|
Page(s) | 377 - 393 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20078993 | |
Published online | 16 April 2008 |
Lines in the cosmic microwave background spectrum from the epoch of cosmological helium recombination
1
Instituto de Astrofisica de Canarias (IAC), C/Via Lactea, s/n, 38200, La Laguna, Tenerife, Spain e-mail: jalberto@iac.es
2
Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching bei München, Germany e-mail: jchluba@mpa-garching.mpg.de
3
Space Research Institute, Russian Academy of Sciences, Profsoyuznaya 84/32, 117997 Moscow, Russia
Received:
5
November
2007
Accepted:
29
February
2008
The main goal of this work is to calculate the contributions of
bound-bound transitions of helium to the cosmological recombination spectrum.
We show that helium in the early Universe causes unique features to appear in
the total cosmological recombination spectrum. These may provide a unique
observational possibility to determine the relative abundance of primordial
helium, well before the formation of first stars.
We include the effect of the tiny fraction of neutral hydrogen atoms on the
dynamics of He II He I recombination at redshifts
z ~ 2500. As discussed recently, this process significantly accelerates
He II
He I recombination, resulting in rather
narrow and distinct features in the associated recombination spectrum.
In addition this process induces some emission within the hydrogen
Lyman-α line, before the actual epoch of hydrogen recombination around
z ~ 1100-1500.
We also show that some of the fine-structure transitions of neutral helium
appear in absorption, again leaving unique traces in the cosmic microwave
background blackbody spectrum, which may allow confirmation of our understanding of
the early Universe and of detailed atomic physics.
Key words: atomic processes / cosmology: cosmic microwave background / cosmology: theory / cosmology: early Universe
© ESO, 2008
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