The imprint of cosmological hydrogen recombination lines on the power spectrum of the CMB

Free access article

Issue		A&A Volume 438, Number 2, August I 2005


Page(s)		461 - 473
Section		Cosmology (including clusters of galaxies)
DOI		http://dx.doi.org/10.1051/0004-6361:20052939

A&A 438, 461-473 (2005)
DOI: 10.1051/0004-6361:20052939

The imprint of cosmological hydrogen recombination lines on the power spectrum of the CMB

J. A. Rubiño-Martín^{1, 2}, C. Hernández-Monteagudo¹ and R. A. Sunyaev^{1, 3}

¹ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str.1, Postfach 1317, 85741 Garching, Germany
e-mail: jalberto@iac.es
² Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
³ Space Research Institute (IKI), Russian Academy of Sciences, Moscow, Russia

(Received 25 February 2005 / Accepted 24 March 2005 )

Abstract
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 $0.3~\mu{\rm K}$ for the H $\alpha$ line, being maximum at small angular scales ( $\ell \approx 870$ ). The morphology of the signal is very rich. It leads to relatively narrow spectral features ( $\Delta \nu / \nu \sim 10^{-1}$ ), 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.

Key words: cosmic microwave background -- cosmology: theory -- early Universe -- atomic processes

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.