The Simons Observatory: Pipeline comparison and validation for large-scale B-modes

Wolz, Kevin, Azzoni, Susanna, Hervías-Caimapo, Carlos, Errard, Josquin, Krachmalnicoff, Nicoletta, Alonso, David, Baccigalupi, Carlo, Baleato Lizancos, Antón, Brown, Michael L., Calabrese, Erminia ORCID: https://orcid.org/0000-0003-0837-0068, Chluba, Jens, Dunkley, Jo, Fabbian, Giulio ORCID: https://orcid.org/0000-0002-3255-4695, Galitzki, Nicholas, Jost, Baptiste, Morshed, Magdy and Nati, Federico 2024. The Simons Observatory: Pipeline comparison and validation for large-scale B-modes. Astronomy & Astrophysics 686 , A16. 10.1051/0004-6361/202346105

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Abstract

Context. The upcoming Simons Observatory Small Aperture Telescopes aim at achieving a constraint on the primordial tensor-to-scalar ratio r at the level of σ(r = 0)≲0.003, observing the polarized CMB in the presence of partial sky coverage, cosmic variance, inhomogeneous non-white noise, and Galactic foregrounds. Aims. We present three different analysis pipelines able to constrain r given the latest available instrument performance, and compare their predictions on a set of sky simulations that allow us to explore a number of Galactic foreground models and elements of instrumental noise, relevant for the Simons Observatory. Methods. The three pipelines employ different combinations of parametric and non-parametric component separation at the map and power spectrum levels, and use B-mode purification to estimate the CMB B-mode power spectrum. We applied them to a common set of simulated realistic frequency maps, and compared and validated them with focus on their ability to extract robust constraints on the tensor-to-scalar ratio r. We evaluated their performance in terms of bias and statistical uncertainty on this parameter. Results. In most of the scenarios the three methodologies achieve similar performance. Nevertheless, several simulations with complex foreground signals lead to a > 2σ bias on r if analyzed with the default versions of these pipelines, highlighting the need for more sophisticated pipeline components that marginalize over foreground residuals. We show two such extensions, using power-spectrum-based and map-based methods, that are able to fully reduce the bias on r below the statistical uncertainties in all foreground models explored, at a moderate cost in terms of σ(r).

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Publisher:	EDP Sciences
ISSN:	0004-6361
Date of First Compliant Deposit:	7 June 2024
Date of Acceptance:	5 March 2024
Last Modified:	10 Jun 2024 09:16
URI:	https://orca.cardiff.ac.uk/id/eprint/169615

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