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Title: SEMI-BLIND EIGEN ANALYSES OF RECOMBINATION HISTORIES USING COSMIC MICROWAVE BACKGROUND DATA

Abstract

Cosmological parameter measurements from cosmic microwave background (CMB) experiments, such as Planck, ACTPol, SPTPol, and other high-resolution follow-ons, fundamentally rely on the accuracy of the assumed recombination model or one with well-prescribed uncertainties. Deviations from the standard recombination history might suggest new particle physics or modified atomic physics. Here we treat possible perturbative fluctuations in the free electron fraction, X{sub e}(z), by a semi-blind expansion in densely packed modes in redshift. From these we construct parameter eigenmodes, which we rank order so that the lowest modes provide the most power to probe X{sub e}(z) with CMB measurements. Since the eigenmodes are effectively weighed by the fiducial X{sub e} history, they are localized around the differential visibility peak, allowing for an excellent probe of hydrogen recombination but a weaker probe of the higher redshift helium recombination and the lower redshift highly neutral freezeout tail. We use an information-based criterion to truncate the mode hierarchy and show that with even a few modes the method goes a long way from the fiducial recombination model computed with RECFAST, X{sub e,i}(z), toward the precise underlying history given by the new and improved recombination calculations of COSMOREC or HYREC, X{sub e,f}(z), in the hydrogen recombinationmore » regime, though not well in the helium regime. Without such a correction, the derived cosmic parameters are biased. We discuss an iterative approach for updating the eigenmodes to further hone in on X{sub e,f}(z) if large deviations are indeed found. We also introduce control parameters that downweight the attention on the visibility peak structure, e.g., focusing the eigenmode probes more strongly on the X{sub e}(z) freezeout tail, as would be appropriate when looking for the X{sub e} signature of annihilating or decaying elementary particles.« less

Authors:
; ;  [1]
  1. Canadian Institute for Theoretical Astrophysics, 60 St. George, Toronto, ON M5S 3H8 (Canada)
Publication Date:
OSTI Identifier:
22037045
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 752; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCURACY; ASTRONOMY; ASTROPHYSICS; CORRECTIONS; COSMIC ELECTRONS; COSMOLOGY; DATA ANALYSIS; FLUCTUATIONS; HELIUM; HYDROGEN; ITERATIVE METHODS; PROBES; RECOMBINATION; RED SHIFT; RELICT RADIATION; RESOLUTION

Citation Formats

Farhang, M., Bond, J. R., and Chluba, J. SEMI-BLIND EIGEN ANALYSES OF RECOMBINATION HISTORIES USING COSMIC MICROWAVE BACKGROUND DATA. United States: N. p., 2012. Web. doi:10.1088/0004-637X/752/2/88.
Farhang, M., Bond, J. R., & Chluba, J. SEMI-BLIND EIGEN ANALYSES OF RECOMBINATION HISTORIES USING COSMIC MICROWAVE BACKGROUND DATA. United States. doi:10.1088/0004-637X/752/2/88.
Farhang, M., Bond, J. R., and Chluba, J. Wed . "SEMI-BLIND EIGEN ANALYSES OF RECOMBINATION HISTORIES USING COSMIC MICROWAVE BACKGROUND DATA". United States. doi:10.1088/0004-637X/752/2/88.
@article{osti_22037045,
title = {SEMI-BLIND EIGEN ANALYSES OF RECOMBINATION HISTORIES USING COSMIC MICROWAVE BACKGROUND DATA},
author = {Farhang, M. and Bond, J. R. and Chluba, J.},
abstractNote = {Cosmological parameter measurements from cosmic microwave background (CMB) experiments, such as Planck, ACTPol, SPTPol, and other high-resolution follow-ons, fundamentally rely on the accuracy of the assumed recombination model or one with well-prescribed uncertainties. Deviations from the standard recombination history might suggest new particle physics or modified atomic physics. Here we treat possible perturbative fluctuations in the free electron fraction, X{sub e}(z), by a semi-blind expansion in densely packed modes in redshift. From these we construct parameter eigenmodes, which we rank order so that the lowest modes provide the most power to probe X{sub e}(z) with CMB measurements. Since the eigenmodes are effectively weighed by the fiducial X{sub e} history, they are localized around the differential visibility peak, allowing for an excellent probe of hydrogen recombination but a weaker probe of the higher redshift helium recombination and the lower redshift highly neutral freezeout tail. We use an information-based criterion to truncate the mode hierarchy and show that with even a few modes the method goes a long way from the fiducial recombination model computed with RECFAST, X{sub e,i}(z), toward the precise underlying history given by the new and improved recombination calculations of COSMOREC or HYREC, X{sub e,f}(z), in the hydrogen recombination regime, though not well in the helium regime. Without such a correction, the derived cosmic parameters are biased. We discuss an iterative approach for updating the eigenmodes to further hone in on X{sub e,f}(z) if large deviations are indeed found. We also introduce control parameters that downweight the attention on the visibility peak structure, e.g., focusing the eigenmode probes more strongly on the X{sub e}(z) freezeout tail, as would be appropriate when looking for the X{sub e} signature of annihilating or decaying elementary particles.},
doi = {10.1088/0004-637X/752/2/88},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 752,
place = {United States},
year = {2012},
month = {6}
}