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A New Limit on CMB Circular Polarization from SPIDER
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Number of Authors: 612017 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 844, no 2, article id 151Article in journal (Refereed) Published
Abstract [en]

We present a new upper limit on cosmic microwave background (CMB) circular polarization from the 2015 flight of SPIDER, a balloon-borne telescope designed to search for B-mode linear polarization from cosmic inflation. Although the level of circular polarization in the CMB is predicted to be very small, experimental limits provide a valuable test of the underlying models. By exploiting the nonzero circular-to-linear polarization coupling of the half-wave plate polarization modulators, data from SPIDER's 2015 Antarctic flight provide a constraint on Stokes V at 95 and 150 GHz in the range 33 < l < 307. No other limits exist over this full range of angular scales, and SPIDER improves on the previous limit by several orders of magnitude, providing 95% C.L. constraints on l (l + 1)C-l(VV) /(2 pi) ranging from 141 to 255 mu K-2 at 150 GHz for a thermal CMB spectrum. As linear CMB polarization experiments become increasingly sensitive, the techniques described in this paper can be applied to obtain even stronger constraints on circular polarization.

Place, publisher, year, edition, pages
2017. Vol. 844, no 2, article id 151
Keywords [en]
cosmic background radiation
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-145843DOI: 10.3847/1538-4357/aa7cfdISI: 000406841700004OAI: oai:DiVA.org:su-145843DiVA, id: diva2:1135776
Available from: 2017-08-24 Created: 2017-08-24 Last updated: 2020-01-23Bibliographically 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)
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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, Adri J.Freese, KatherineGudmundsson, Jón E.
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