Primordial helium recombination III: Thomson scattering, isotope shifts, and cumulative results

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dc.creatorSwitzer, Eric R.
dc.creatorHirata, Christopher M.
dc.date2007-02-06
dc.date2008-05-20
dc.date.accessioned2026-07-07T11:42:45Z
dc.date.available2026-07-07T11:42:45Z
dc.descriptionUpcoming precision measurements of the temperature anisotropy of the cosmic microwave background (CMB) at high multipoles will need to be complemented by a more complete understanding of recombination, which determines the damping of anisotropies on these scales. This is the third in a series of papers describing an accurate theory of HeI and HeII recombination. Here we describe the effect of Thomson scattering, the $^3$He isotope shift, the contribution of rare decays, collisional processes, and peculiar motion. These effects are found to be negligible: Thomson and $^3$He scattering modify the free electron fraction $x_e$ at the level of several $\times 10^{-4}$. The uncertainty in the $2^3P^o-1^1S$ rate is significant, and for conservative estimates gives uncertainties in $x_e$ of order $10^{-3}$. We describe several convergence tests for the atomic level code and its inputs, derive an overall $C_\ell$ error budget, and relate shifts in $x_e(z)$ to the changes in $C_\ell$, which are at the level of 0.5% at $\ell =3000$. Finally, we summarize the main corrections developed thus far. The remaining uncertainty from known effects is $\sim 0.3%$ in $x_e$.
dc.description19 pages, 15 figures, to be submitted to PRD
dc.identifierhttps://arxiv.org/abs/astro-ph/0702145
dc.identifierhttp://arxiv.org/abs/astro-ph/0702145
dc.identifierPhys.Rev.D77:083008,2008
dc.identifierdoi:10.1103/PhysRevD.77.083008
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/200999
dc.subjectAstrophysics
dc.titlePrimordial helium recombination III: Thomson scattering, isotope shifts, and cumulative results
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