Title: Mitigating the optical depth degeneracy using the kinematic Sunyaev-Zel’dovich effect with CMB-S4 data

Abstract

The epoch of reionization is one of the major phase transitions in the history of the universe, and is a focus of ongoing and upcoming cosmic microwave background (CMB) experiments with improved sensitivity to small-scale fluctuations. Reionization also represents a significant contaminant to CMB-derived cosmological parameter constraints, due to the degeneracy between the Thomson-scattering optical depth, $$\tau$$, and the amplitude of scalar perturbations, $$A_s$$. This degeneracy subsequently hinders the ability of large-scale structure data to constrain the sum of the neutrino masses, a major target for cosmology in the 2020s. In this work, we explore the kinematic Sunyaev-Zel'dovich (kSZ) effect as a probe of reionization, and show that it can be used to mitigate the optical depth degeneracy with high-sensitivity, high-resolution data from the upcoming CMB-S4 experiment. We discuss the dependence of the kSZ power spectrum on physical reionization model parameters, as well as on empirical reionization parameters, namely $$\tau$$ and the duration of reionization, $$\Delta z$$. We show that by combining the kSZ two-point function and the reconstructed kSZ four-point function, degeneracies between $$\tau$$ and $$\Delta z$$ can be strongly broken, yielding tight constraints on both parameters. We forecast $$\sigma(\tau) = 0.003$$ and $$\sigma(\Delta z) = 0.25$$ for a combination of CMB-S4 and Planck data, including detailed treatment of foregrounds and atmospheric noise. The constraint on $$\tau$$ is nearly identical to the cosmic-variance limit that can be achieved from large-angle CMB polarization data. The kSZ effect thus promises to yield not only detailed information about the reionization epoch, but also to enable high-precision cosmological constraints on the neutrino mass.

Authors:

Alvarez, Marcelo A. ^[1]; Ferraro, Simone  ^[2];

• Search DOE PAGES for author "Ferraro, Simone"
• Search DOE PAGES for ORCID "0000-0003-4992-7854"

Hill, J. Colin  ^[3];

• Search DOE PAGES for author "Hill, J. Colin"
• Search DOE PAGES for ORCID "0000-0002-9539-0835"

Hložek, Renée ^[4]; Ikape, Margaret ^[4]

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+ Show Author Affiliations

1. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)
3. Columbia Univ., New York, NY (United States); Flatiron Inst., New York, NY (United States)
4. Univ. of Toronto, ON (Canada)

Publication Date:

Wed Mar 17 00:00:00 EDT 2021

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), High Energy Physics (HEP); Simons Foundation; Natural Sciences and Engineering Research Council of Canada (NSERC); Canadian Institute for Advanced Research (CIFAR)

OSTI Identifier:

1771973

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review D

Additional Journal Information:

Journal Volume: 103; Journal Issue: 6; Journal ID: ISSN 2470-0010

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

79 ASTRONOMY AND ASTROPHYSICS