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Full-sky beam convolution for cosmic microwave background applications
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
2019 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 486, no 4, p. 5448-5467Article in journal (Refereed) Published
Abstract [en]

We introduce a publicly available full-sky beam convolution code library intended to inform the design of future cosmic microwave background instruments and help current experiments probe potential systematic effects. The code can be used to assess the impact of optical systematics on all stages of data reduction for a realistic experiment, including analyses beyond power spectrum estimation, by generating signal timelines that may serve as input to full analysis pipelines. The design and mathematical framework of the PYTHON code is discussed along with a few simple benchmarking results. We present a simple two-lens refracting telescope design and use it together with the code to simulate a year-long data set for 400 detectors scanning the sky on a satellite instrument. The simulation results identify a number of sub-leading optical non-idealities and demonstrate significant B-mode residuals caused by extended sidelobes that are sensitive to polarized radiation from the Galaxy. For the proposed design and satellite scanning strategy, we show that a full physical optics beam model generates B-mode systematics that differ significantly from the simpler elliptical Gaussian model.

Place, publisher, year, edition, pages
2019. Vol. 486, no 4, p. 5448-5467
Keywords [en]
Cosmic Background Radiation, Cosmology: observations, Techniques: polarimetric, Telescopes
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-171281DOI: 10.1093/mnras/stz1143ISI: 000474908200074OAI: oai:DiVA.org:su-171281DiVA, id: diva2:1340540
Available from: 2019-08-05 Created: 2019-08-05 Last updated: 2019-08-19Bibliographically approved
In thesis
1. Probing the early Universe with B-mode polarization: The Spider instrument, optical modelling and non-Gaussianity
Open this publication in new window or tab >>Probing the early Universe with B-mode polarization: The Spider instrument, optical modelling and non-Gaussianity
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

One of the main goals of modern observational cosmology is to constrain or detect a stochastic background of primordial gravitational waves. The existence of such a background is a generic prediction of the inflationary paradigm: the leading explanation for the universe's initial perturbations. A detection of the gravitational wave signal would provide strong evidence for the paradigm and would amount to an indirect probe of an energy scale far beyond that of conventional physics. Several dedicated experiments search for the signal by performing highly accurate measurements of a unique probe of the primordial gravitational wave background: the B-mode signature in the polarization of the cosmic microwave background (CMB) radiation. A part of this thesis is devoted to one of these experiments: the balloon-borne Spider instrument. The analysis of the first dataset, obtained in two (95 and 150 GHz) frequency bands during a January 2015 Antarctic flight, is described, along with details on the characterisation of systematic signal and the calibration of the instrument. The case of systematic signal due to poorly understood optical properties is treated in more detail. In the context of upcoming experiments, a study of systematic optical effects is presented as well as a numerically efficient method to consistently propagate such effects through an analysis pipeline. This is achieved by a `beam convolution' algorithm capable of simulating the contribution from the entire sky, weighted by the optical response, to the instrument's time-ordered data. It is described how the algorithm can be employed to forecast the performance of upcoming CMB experiments. In the final part of the thesis, an additional use of upcoming B-mode data is described. Constraints on the non-Gaussian correlation between the large-angular-scale B-mode field and the CMB temperature or E-mode anisotropies on small angular scales constitute a rigorous consistency check of the inflationary paradigm. An efficient statistical estimation procedure, a generalised bispectrum estimator, is derived and the constraining power of upcoming CMB data is explored.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2019
Keywords
cosmic microwave background, early universe, polarimetry, telescopes
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-171284 (URN)978-91-7797-799-5 (ISBN)978-91-7797-800-8 (ISBN)
Public defence
2019-09-20, sal FD41, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 1: Manuscript.

Available from: 2019-08-28 Created: 2019-08-12 Last updated: 2019-08-20Bibliographically approved

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Duivenvoorden, Adriaan J.Gudmundsson, Jon E.
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