Cosmological hydrogen recombination: The effect of extremely high-n states

Journal Article · Thu Apr 15 04:00:00 EDT 2010 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.81.083005· OSTI ID:21409552

Grin, Daniel; Hirata, Christopher M ^[1]

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1. California Institute of Technology, Mail Code 350-17, Pasadena, California 91125 (United States)

Calculations of cosmological hydrogen recombination are vital for the extraction of cosmological parameters from cosmic microwave background (CMB) observations, and for imposing constraints to inflation and reionization. The Planck mission and future experiments will make high precision measurements of CMB anisotropies at angular scales as small as l{approx}2500, necessitating a calculation of recombination with fractional accuracy of {approx_equal}10{sup -3}. Recent work on recombination includes two-photon transitions from high excitation states and many radiative transfer effects. Modern recombination calculations separately follow angular momentum sublevels of the hydrogen atom to accurately treat nonequilibrium effects at late times (z<900). The inclusion of extremely high-n (n> or approx. 100) states of hydrogen is then computationally challenging, preventing until now a determination of the maximum n needed to predict CMB anisotropy spectra with sufficient accuracy for Planck. Here, results from a new multilevel-atom code (RecSparse) are presented. For the first time, 'forbidden' quadrupole transitions of hydrogen are included, but shown to be negligible. RecSparse is designed to quickly calculate recombination histories including extremely high-n states in hydrogen. Histories for a sequence of values as high as n{sub max}=250 are computed, keeping track of all angular momentum sublevels and energy shells of the hydrogen atom separately. Use of an insufficiently high n{sub max} value (e.g., n{sub max}=64) leads to errors (e.g., 1.8{sigma} for Planck) in the predicted CMB power spectrum. Extrapolating errors, the resulting CMB anisotropy spectra are converged to {approx}0.5{sigma} at Fisher-matrix level for n{sub max}=128, in the purely radiative case.

• OSTI ID: 21409552
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 8 Vol. 81; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ACCURACY
ANGULAR MOMENTUM
ANISOTROPY
ATOMS
BOSONS
COMPUTERIZED SIMULATION
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
ELEMENTS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXTRACTION
HEAT TRANSFER
HYDROGEN
MASSLESS PARTICLES
MICROWAVE RADIATION
NONMETALS
PHOTONS
RADIANT HEAT TRANSFER
RADIATIONS
RECOMBINATION
RELICT RADIATION
SEPARATION PROCESSES
SIMULATION
SPECTRA