Eliminating the optical depth nuisance from the CMB with 21 cm cosmology
File(s)
Accepted version
OA Location
Author(s)
Type
Journal Article
Abstract
Amongst standard model parameters that are constrained by cosmic microwave background (CMB) observations, the optical depth τ stands out as a nuisance parameter. While τ provides some crude limits on reionization, it also degrades constraints on other cosmological parameters. Here we explore how 21 cm cosmology—as a direct probe of reionization—can be used to independently predict τ in an effort to improve CMB parameter constraints. We develop two complementary schemes for doing so. The first uses 21 cm power spectrum observations in conjunction with semianalytic simulations to predict τ. The other uses global 21 cm measurements to directly constrain low redshift (post-reheating) contributions to τ in a relatively model-independent way. Forecasting the performance of the upcoming hydrogen epoch of reionization array, we find that significant reductions in the errors on τ can be achieved. These results are particularly effective at breaking the CMB degeneracy between τ and the amplitude of the primordial fluctuation spectrum As, with errors on ln(1010As) reduced by up to a factor of 4. Stage 4 CMB constraints on the neutrino mass sum are also improved, with errors potentially reduced to 12 meV regardless of whether CMB experiments can precisely measure the reionization bump in polarization power spectra. Observations of the 21 cm line are therefore capable of improving not only our understanding of reionization astrophysics, but also of cosmology in general.
Date Issued
2016-02-19
Date Acceptance
2015-11-12
Citation
Physical Review D, 2016, 93 (4)
ISSN
1550-7998
Publisher
American Physical Society
Journal / Book Title
Physical Review D
Volume
93
Issue
4
Copyright Statement
© 2016 American Physical Society
Sponsor
Commission of the European Communities
Commission of the European Communities
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000370618800002&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Grant Number
321933
638743
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
Physics, Particles & Fields
Physics
RADIATIVE-TRANSFER SIMULATIONS
SELF-REGULATED REIONIZATION
LIGHT-CONE ANISOTROPY
LARGE-SCALE STRUCTURE
ALPHA FOREST DATA
SIMILAR-TO 20
COSMIC REIONIZATION
POWER SPECTRUM
HIGH-REDSHIFT
DARK-MATTER
Nuclear & Particles Physics
0201 Astronomical And Space Sciences
0202 Atomic, Molecular, Nuclear, Particle And Plasma Physics
0206 Quantum Physics
Publication Status
Published
Article Number
ARTN 043013