TITLE:
Primordial helium recombination III: Thomson scattering, isotope shifts, and cumulative results.
AUTHOR(S):
Eric R. Switzer (Princeton); Christopher M. Hirata (IAS).
DATE:
2007 Feb 06 (arXiv, posted, v1);
2007 Mar 11 (Phys. Rev. D, submitted);
2008 Feb 12 (revised);
2008 Feb 24 (Phys. Rev. D, accepted);
2008 Apr 30 (Phys. Rev. D, published);
2008 May 20 (arXiv, posted, v2).
AVAILABILITY:
arXiv astro-ph/0702145 (free);
APS (requires subscription).
PUBLICATION INFORMATION:
Phys. Rev. D 77, 083008 (2008).
ABSTRACT:
Upcoming 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 3He isotope
shift, the contribution of rare decays, collisional processes, and peculiar motion. These effects are found to be negligible: Thomson and
3He scattering modify the free electron fraction xe at the level of several x10-4. The uncertainty in the
23Po-11S rate is significant, and for conservative estimates gives uncertainties in xe of order
10-3. We describe several convergence tests for the atomic level code and its inputs, derive an overall CL error budget, and
relate shifts in xe(z) to the changes in CL, which are at the level of 0.5% at L=3000. Finally, we summarize the main corrections
developed thus far. The remaining uncertainty from known effects is ~0.3% in xe$.
ADS BIBLIOGRAPHIC CODE: 2008PhRvD..77h3008S
COMMENTS:
This is the last in a series of three papers on helium recombination; see Paper I and Paper
II.