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Title: BICEP2 III: Instrumental systematics

In a companion paper, we have reported a >5σ detection of degree scale B-mode polarization at 150 GHz by the Bicep2 experiment. Here we provide a detailed study of potential instrumental systematic contamination to that measurement. We focus extensively on spurious polarization that can potentially arise from beam imperfections. We present a heuristic classification of beam imperfections according to their symmetries and uniformities, and discuss how resulting contamination adds or cancels in maps that combine observations made at multiple orientations of the telescope about its boresight axis. We introduce a technique, which we call "deprojection," for filtering the leading order beam-induced contamination from time-ordered data, and show that it reduces power in Bicep2's actual and null-test BB spectra consistent with predictions using high signal-to-noise beam shape measurements. We detail the simulation pipeline that we use to directly simulate instrumental systematics and the calibration data used as input to that pipeline. Finally, we present the constraints on BB contamination from individual sources of potential systematics. We find that systematics contribute BB power that is a factor of ~10× below Bicep2's three-year statistical uncertainty, and negligible compared to the observed BB signal. Lastly, the contribution to the best-fit tensor/scalar ratio is atmore » a level equivalent to r = (3–6) × 10–3.« less
  1. Cardiff Univ., Cardiff (United Kingdom). et al.
Publication Date:
Report Number(s):
Journal ID: ISSN 1538-4357; arXiv:1502.00608
Grant/Contract Number:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 814; Journal Issue: 2; Journal ID: ISSN 1538-4357
Institute of Physics (IOP)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Contributing Orgs:
Bicep2 Collaboration
Country of Publication:
United States
79 ASTRONOMY AND ASTROPHYSICS; astrophysics; ASTRO; cosmic background radiation; cosmology: observations; gravitational waves; inflation; instrumentation: polarimeters; methods: data analysis
OSTI Identifier: