BICEP2/Keck Array XI: Beam Characterization and Temperature-to-Polarization Leakage in the BK15 Data Set

Journal Article · 15 October 2019 · The Astrophysical Journal (Online)

DOI: https://doi.org/10.3847/1538-4357/ab391d · OSTI ID:1596971

Ade, P. A. R. ; Ahmed, Z.; Aikin, R. W.; Barkats, D. ; Benton, S. J.; Bischoff, C. A. ; Bock, J. J.; Bowens-Rubin, R.; Brevik, J. A.; Buder, I.; Bullock, E.; Buza, V.; Connors, J.; Cornelison, J.; Crill, B. P. ; Crumrine, M.; Dierickx, M. ; Duband, L.; Filippini, J. P. ; Fliescher, S. ; Grayson, J.; Hall, G.; Halpern, M. ; Harrison, S.; Hildebrandt, S. R.; Hilton, G. C.; Hui, H.; Irwin, K. D.; Kang, J.; Karkare, K. S. ; Karpel, E.; Kaufman, J. P.; Keating, B. G.; Kefeli, S.; Kernasovskiy, S. A.; Kovac, J. M.; Kuo, C. L.; Larsen, N. A.; Lau, K.; Leitch, E. M.; Lueker, M.; Megerian, K. G.; Moncelsi, L. ; Namikawa, T.; Netterfield, C. B.; Nguyen, H. T.; O’Brient, R.; IV, R. W. Ogburn; Palladino, S.; Pryke, C.; Racine, B.; Richter, S.; Schillaci, A.; Schwarz, R.; Sheehy, C. D.; Soliman, A.; Germaine, T. St.; Staniszewski, Z. K.; Steinbach, B.; Sudiwala, R. V.; Teply, G. P.; Thompson, K. L.; Tolan, J. E.; Tucker, C.; Turner, A. D.; Umilta, C.; Vieregg, A. G.; Wandui, A.; Weber, A. C.; Wiebe, D. V.; Willmert, J.; Wong, C. L.; Wu, W. L. K. ; Yang, H.; Yoon, K. W.; Zhang, C.

Precision measurements of cosmic microwave background (CMB) polarization require extreme control of instrumental systematics. In a companion paper we have presented cosmological constraints from observations with the BICEP2 and Keck Array experiments up to and including the 2015 observing season (BK15), resulting in the deepest CMB polarization maps to date and a statistical sensitivity to the tensor-to-scalar ratio of σ(r) = 0.020. In this work we characterize the beams and constrain potential systematic contamination from main beam shape mismatch at the three BK15 frequencies (95, 150, and 220 GHz). Herein far-field maps of 7360 distinct beam patterns taken from 2010–2015 are used to measure differential beam parameters and predict the contribution of temperature-to-polarization leakage to the BK15 B-mode maps. In the multifrequency, multicomponent likelihood analysis that uses BK15, Planck, and Wilkinson Microwave Anisotropy Probe maps to separate sky components, we find that adding this predicted leakage to simulations induces a bias of Δr = 0.0027 ± 0.0019. Future results using higher-quality beam maps and improved techniques to detect such leakage in CMB data will substantially reduce this uncertainty, enabling the levels of systematics control needed for BICEP Array and other experiments that plan to definitively probe large-field inflation.

• Research Organization: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
• Sponsoring Organization: National Aeronautic and Space Administration (NASA); National Science Foundation (NSF); USDOE Office of Science (SC)
• Contributing Organization: Keck Array and BICEP2 Collaborations
• Grant/Contract Number: AC02-76SF00515
• OSTI ID: 1596971
• Report Number(s): arXiv:1904.01640v2
• Journal Information: The Astrophysical Journal (Online), Journal Name: The Astrophysical Journal (Online) Journal Issue: 2 Vol. 884; ISSN 1538-4357
• Publisher: Institute of Physics (IOP)Copyright Statement
• Country of Publication: United States
• Language: English