The Simons Observatory: impact of bandpass, polarization angle and calibration uncertainties on small-scale power spectrum analysis

Giardiello, S., Gerbino, M., Pagano, L., Alonso, D., Beringue, B., Bolliet, B., Calabrese, E. ORCID: https://orcid.org/0000-0003-0837-0068, Coppi, G., Errard, J., Fabbian, G. ORCID: https://orcid.org/0000-0002-3255-4695, Harrison, I. ORCID: https://orcid.org/0000-0002-4437-0770, Hill, J.C., Jense, H.T., Keating, B., La Posta, A., Lattanzi, M., Lonappan, A.I., Puglisi, G., Reichardt, C.L. and Simon, S.M. 2024. The Simons Observatory: impact of bandpass, polarization angle and calibration uncertainties on small-scale power spectrum analysis. Journal of Cosmology and Astroparticle Physics 2024 , 008. 10.1088/1475-7516/2024/09/008

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Abstract

We study the effects due to mismatches in passbands, polarization angles, and temperature and polarization calibrations in the context of the upcoming cosmic microwave background experiment Simons Observatory (SO). Using the SO multi-frequency likelihood, we estimate the bias and the degradation of constraining power in cosmological and astrophysical foreground parameters assuming different levels of knowledge of the instrumental effects. We find that incorrect but reasonable assumptions about the values of all the systematics examined here can have significant effects on cosmological analyses, hence requiring marginalization approaches at the likelihood level. When doing so, we find that the most relevant effect is due to bandpass shifts. When marginalizing over them, the posteriors of parameters describing astrophysical microwave foregrounds (such as radio point sources or dust) get degraded, while cosmological parameters constraints are not significantly affected. Marginalization over polarization angles with up to 0.25° uncertainty causes an irrelevant bias ≲ 0.05 σ in all parameters. Marginalization over calibration factors in polarization broadens the constraints on the effective number of relativistic degrees of freedom Neff by a factor 1.2, interpreted here as a proxy parameter for non standard model physics targeted by high-resolution CMB measurements.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Physics and Astronomy
Publisher:	IOP Publishing
ISSN:	1475-7516
Date of First Compliant Deposit:	4 September 2024
Date of Acceptance:	8 August 2024
Last Modified:	04 Sep 2024 15:30
URI:	https://orca.cardiff.ac.uk/id/eprint/171773

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