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The Simons Observatory: Bandpass and polarization-angle calibration requirements for B-mode searches

Abstract:
We quantify the calibration requirements for systematic uncertainties for next-generation ground-based observatories targeting the large-angle B-mode polarization of the Cosmic Microwave Background, with a focus on the Simons Observatory (SO). We explore uncertainties on gain calibration, bandpass center frequencies, and polarization angles, including the frequency variation of the latter across the bandpass. We find that gain calibration and bandpass center frequencies must be known to percent levels or less to avoid biases on the tensor-to-scalar ratio r on the order of Δ r~10-3, in line with previous findings. Polarization angles must be calibrated to the level of a few tenths of a degree, while their frequency variation between the edges of the band must be known to O(10) degrees. Given the tightness of these calibration requirements, we explore the level to which residual uncertainties on these systematics would affect the final constraints on r if included in the data model and marginalized over. We find that the additional parameter freedom does not degrade the final constraints on r significantly, broadening the error bar by O(10%) at most. We validate these results by reanalyzing the latest publicly available data from the collaboration within an extended parameter space covering both cosmological, foreground and systematic parameters. Finally, our results are discussed in light of the instrument design and calibration studies carried out within SO.
Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.1088/1475-7516/2021/05/032

Authors


More by this author
Institution:
University of Oxford
Department:
PHYSICS
Sub department:
Astrophysics
Role:
Author
ORCID:
0000-0001-8071-6735
More by this author
Institution:
University of Oxford
Department:
PHYSICS
Sub department:
Astrophysics
Oxford college:
Christ Church; St Peter's; Christ Church; St Peter's; Christ Church; St Peter's; Christ Church; St Peter's; Christ Church
Role:
Author
ORCID:
0000-0002-4598-9719


Publisher:
IOP Publishing
Journal:
Journal of Cosmology and Astroparticle Physics More from this journal
Volume:
2021
Issue:
5
Article number:
032
Publication date:
2021-05-13
Acceptance date:
2021-03-27
DOI:
EISSN:
1475-7516


Language:
English
Keywords:
Pubs id:
1140890
Local pid:
pubs:1140890
Deposit date:
2021-06-06

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