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Barkats, Denis

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Barkats, Denis
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    Detection of B-Mode Polarization at Degree Angular Scales by BICEP2
    (American Physical Society (APS), 2014) Ade, P. A. R.; Aikin, R. W.; Barkats, Denis; Benton, S. J.; Bischoff, Colin; Bock, J. J.; Brevik, J. A.; Buder, I; Bullock, E.; Dowell, C. D.; Duband, L.; Filippini, J. P.; Fliescher, S.; Golwala, S. R.; Halpern, M.; Hasselfield, M.; Hildebrandt, S. R.; Hilton, G. C.; Hristov, V. V.; Irwin, K. D.; Karkare, Kirit; Kaufman, J. P.; Keating, B. G.; Kernasovskiy, S. A.; Kovac, John; Kuo, C. L.; Leitch, E. M.; Lueker, M.; Mason, P.; Netterfield, C. B.; Nguyen, H. T.; O’Brient, R.; Ogburn, R. W.; Orlando, Abigail; Pryke, C; Reintsema, C. D.; Richter, Sonja Valeska; Schwarz, R.; Sheehy, C. D.; Staniszewski, Z. K.; Sudiwala, R. V.; Teply, G. P.; Tolan, J. E.; Turner, A. D.; Vieregg, A. G.; Wong, C; Yoon, K. W.
    We report results from the BICEP2 experiment, a cosmic microwave background (CMB) polarimeter specifically designed to search for the signal of inflationary gravitational waves in the B-mode power spectrum around ℓ∼80. The telescope comprised a 26 cm aperture all-cold refracting optical system equipped with a focal plane of 512 antenna coupled transition edge sensor 150 GHz bolometers each with temperature sensitivity of ≈300  μK(CMB)√s. BICEP2 observed from the South Pole for three seasons from 2010 to 2012. A low-foreground region of sky with an effective area of 380 square deg was observed to a depth of 87 nK deg in Stokes Q and U. In this paper we describe the observations, data reduction, maps, simulations, and results. We find an excess of B-mode power over the base lensed-ΛCDM expectation in the range 30 < ℓ < 150, inconsistent with the null hypothesis at a significance of >5σ. Through jackknife tests and simulations based on detailed calibration measurements we show that systematic contamination is much smaller than the observed excess. Cross correlating against WMAP 23 GHz maps we find that Galactic synchrotron makes a negligible contribution to the observed signal. We also examine a number of available models of polarized dust emission and find that at their default parameter values they predict power ∼(5-10)× smaller than the observed excess signal (with no significant cross-correlation with our maps). However, these models are not sufficiently constrained by external public data to exclude the possibility of dust emission bright enough to explain the entire excess signal. Cross correlating BICEP2 against 100 GHz maps from the BICEP1 experiment, the excess signal is confirmed with 3σ significance and its spectral index is found to be consistent with that of the CMB, disfavoring dust at 1.7σ. The observed B-mode power spectrum is well fit by a lensed-ΛCDM+tensor theoretical model with tensor-to-scalar ratio r = 0.20_(-0.05)(+0.07), with r = 0 disfavored at 7.0σ. Accounting for the contribution of foreground, dust will shift this value downward by an amount which will be better constrained with upcoming data sets.
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    bicep2/Keck Array. IV. Optical Characterization and Performance of the Bicep2 and Keck Array Experiments
    (IOP Publishing, 2015) Ade, P. A. R.; Aikin, R. W.; Barkats, Denis; Benton, S. J.; Bischoff, Colin; Bock, J. J.; Bradford, K. J.; Brevik, J. A.; Buder, I; Bullock, E.; Dowell, C. D.; Duband, L.; Filippini, J. P.; Fliescher, S.; Golwala, S. R.; Halpern, M.; Hasselfield, M.; Hildebrandt, S. R.; Hilton, G. C.; Hui, H.; Irwin, K. D.; Kang, J. H.; Karkare, Kirit Sukrit; Kaufman, J. P.; Keating, B. G.; Kefeli, S.; Kernasovskiy, S. A.; Kovac, John; Kuo, C. L.; Leitch, E. M.; Lueker, M.; Megerian, K. G.; Netterfield, C. B.; Nguyen, H. T.; O’Brient, R.; IV, R. W. Ogburn; Orlando, A.; Pryke, C; Richter, Sonja Valeska; Schwarz, R.; Sheehy, C. D.; Staniszewski, Z. K.; Sudiwala, R. V.; Teply, G. P.; Thompson, K.; Tolan, J. E.; Turner, A. D.; Vieregg, A. G.; Weber, A. C.; Wong, C; Yoon, K. W.
    bicep2 and the Keck Array are polarization-sensitive microwave telescopes that observe the cosmic microwave background (CMB) from the South Pole at degree angular scales in search of a signature of inflation imprinted as B-mode polarization in the CMB. bicep2 was deployed in late 2009, observed for three years until the end of 2012 at 150 GHz with 512 antenna-coupled transition edge sensor bolometers, and has reported a detection of B-mode polarization on degree angular scales. The Keck Array was first deployed in late 2010 and will observe through 2016 with five receivers at several frequencies (95, 150, and 220 GHz). bicep2 and the Keck Array share a common optical design and employ the field-proven bicep1 strategy of using small-aperture, cold, on-axis refractive optics, providing excellent control of systematics while maintaining a large field of view. This design allows for full characterization of far-field optical performance using microwave sources on the ground. Here we describe the optical design of both instruments and report a full characterization of the optical performance and beams of bicep2 and the Keck Array at 150 GHz.
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    BICEP2. II. Experiment and three-year data set
    (IOP Publishing, 2014) Ade, P. A. R.; Aikin, R. W.; Amiri, M.; Barkats, Denis; Benton, S. J.; Bischoff, Colin; Bock, J. J.; Brevik, J. A.; Buder, I.; Bullock, E.; Davis, G.; Day, P. K.; Dowell, C. D.; Duband, L.; Filippini, J. P.; Fliescher, S.; Golwala, S. R.; Halpern, M.; Hasselfield, M.; Hildebrandt, S. R.; Hilton, G. C.; Irwin, K. D.; Karkare, Kirit Sukrit; Kaufman, J. P.; Keating, B. G.; Kernasovskiy, S. A.; Kovac, John; Kuo, C. L.; Leitch, E. M.; Llombart, N.; Lueker, M.; Netterfield, C. B.; Nguyen, H. T.; O, R.; Ogburn, R. W.; Orlando, Abigail; Pryke, C; Reintsema, C. D.; Richter, S.; Schwarz, R.; Sheehy, C. D.; Staniszewski, Z. K.; Story, K. T.; Sudiwala, R. V.; Teply, G. P.; Tolan, J. E.; Turner, A. D.; Vieregg, A. G.; Wilson, P.; Wong, C; Yoon, K. W.
    We report on the design and performance of the BICEP2 instrument and on its three-year data set. BICEP2 was designed to measure the polarization of the cosmic microwave background (CMB) on angular scales of 1°-5°(l = 40-200), near the expected peak of the B-mode polarization signature of primordial gravitational waves from cosmic inflation. Measuring B-modes requires dramatic improvements in sensitivity combined with exquisite control of systematics. The BICEP2 telescope observed from the South Pole with a 26 cm aperture and cold, on-axis, refractive optics. BICEP2 also adopted a new detector design in which beam-defining slot antenna arrays couple to transition-edge sensor (TES) bolometers, all fabricated on a common substrate. The antenna-coupled TES detectors supported scalable fabrication and multiplexed readout that allowed BICEP2 to achieve a high detector count of 500 bolometers at 150 GHz, giving unprecedented sensitivity to B-modes at degree angular scales. After optimization of detector and readout parameters, BICEP2 achieved an instrument noise-equivalent temperature of 15.8 μ {K}\sqrt{{s}}. The full data set reached Stokes Q and U map depths of 87.2 nK in square-degree pixels (5.'2 μK) over an effective area of 384 deg2 within a 1000 deg2 field. These are the deepest CMB polarization maps at degree angular scales to date. The power spectrum analysis presented in a companion paper has resulted in a significant detection of B-mode polarization at degree scales.
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    Bicep2/keck Array. Vii. Matrix Basede/bseparation Applied to Bicep2 and the Keck Array
    (American Astronomical Society, 2016) Ade, P. A. R.; Ahmed, Z.; Aikin, R. W.; Alexander, Kate; Barkats, Denis; Benton, S. J.; Bischoff, Colin; Bock, J. J.; Bowens-Rubin, Rachel; Brevik, J. A.; Buder, I; Bullock, E.; Buza, Victor; Connors, Jake Anthony; Crill, B. P.; Duband, L.; Dvorkin, Cora; Filippini, J. P.; Fliescher, S.; Grayson, J.; Halpern, M.; Harrison, Sarah; Hildebrandt, S. R.; Hilton, G. C.; Hui, H.; Irwin, K. D.; Kang, J.; Karkare, Kirit Sukrit; Karpel, E.; Kaufman, J. P.; Keating, B. G.; Kefeli, S.; Kernasovskiy, S. A.; Kovac, John; Kuo, C. L.; Leitch, E. M.; Lueker, M.; Megerian, K. G.; Namikawa, T.; Netterfield, C. B.; Nguyen, H. T.; O’Brient, R.; IV, R. W. Ogburn; Orlando, A.; Pryke, C.; Richter, S.; Schwarz, R.; Sheehy, C. D.; Staniszewski, Z. K.; Steinbach, B.; Sudiwala, R. V.; Teply, G. P.; Thompson, K. L.; Tolan, J. E.; Tucker, C.; Turner, A. D.; Vieregg, A. G.; Weber, A. C.; Wiebe, D. V.; Willmert, J.; Wong, C; Wu, W. L. K.; Yoon, K. W.
    A linear polarization field on the sphere can be uniquely decomposed into an E-mode and a B-mode component. These two components are analytically defined in terms of spin-2 spherical harmonics. Maps that contain filtered modes on a partial sky can also be decomposed into E-mode and B-mode components. However, the lack of full sky information prevents orthogonally separating these components using spherical harmonics. In this paper, we present a technique for decomposing an incomplete map into E and B-mode components using E and B eigenmodes of the pixel covariance in the observed map. This method is found to orthogonally define E and B in the presence of both partial sky coverage and spatial filtering. This method has been applied to the Bicep2 and the Keck Array maps and results in reducing E to B leakage from ΛCDM E-modes to a level corresponding to a tensor-to-scalar ratio of
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    BICEP2 III: Instrumental Systematics
    (IOP Publishing, 2015) Ade, P. A. R.; Aikin, R. W.; Barkats, Denis; Benton, S. J.; Bischoff, Colin; Bock, J. J.; Brevik, J. A.; Buder, I; Bullock, E.; Dowell, C. D.; Duband, L.; Filippini, J. P.; Fliescher, S.; Golwala, S. R.; Halpern, M.; Hasselfield, M.; Hildebrandt, S. R.; Hilton, G. C.; Irwin, K. D.; Karkare, Kirit Sukrit; Kaufman, J. P.; Keating, B. G.; Kernasovskiy, S. A.; Kovac, John; Kuo, C. L.; Leitch, E. M.; Lueker, M.; Netterfield, C. B.; Nguyen, H. T.; O’Brient, R.; IV, R. W. Ogburn; Orlando, Abigail; Pryke, C; Richter, Sonja Valeska; Schwarz, R.; Sheehy, C. D.; Staniszewski, Z. K.; Sudiwala, R. V.; Teply, G. P.; Tolan, J. E.; Turner, A. D.; Vieregg, A. G.; Wong, C; Yoon, K. W.
    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. The contribution to the best-fit tensor/scalar ratio is at a level equivalent to r = (3–6) × 10−3.
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    BICEP2/Keck Array VIII: Measurement of Gravitational Lensing from Large-scale B-Mode Polarization.
    (American Astronomical Society, 2016) Array, The Keck; Ade, BICEP2; Ahmed, Z.; Aikin, R.; Alexander, Kate; Barkats, Denis; Benton, S.; Bischoff, Colin; Bock, J.; Bowens-Rubin, Rachel; Brevik, J.; Buder, I; Bullock, E.; Buza, Victor; Connors, Jake Anthony; Crill, B.; Duband, L.; Dvorkin, Cora; Filippin, J.; Fliescher, S.; Grayson, J.; Halpern, M.; Harrison, Sarah; Hildebrandt, S.; Hilton, G.; Hui, H.; Irwin, K.; Kang, J.; Karkare, Kirit Sukrit; Karpel, E.; Kaufman, J.; Keating, B.; Kefeli, S.; Kernasovskiy, S.; Kovac, John; Kuo, C.; Leitch, E.; Lueker, M.; Megerian, K.; Namikawa, T.; Netterfield, C.; Nguyen, H.; O'Brient, R.; Ogburn, R.; Orlando, A.; Pryke, C.; Richter, Sonja Valeska; Schwarz, R.; Sheehy, C.; Staniszewski, Z.; Steinbach, B.; Sudiwala, R.; Teply, G.; Thompson, K.; Tolan, J.; Tucker, C.; Turner, A.; Vieregg, A.
    We present measurements of polarization lensing using the 150 GHz maps, which include all data taken by the BICEP2 and Keck Array Cosmic Microwave Background polarization experiments up to and including the 2014 observing season (BK14). Despite their modest angular resolution ($\sim 0\buildrel{\circ}\over{.} 5$), the excellent sensitivity (~3μK-arcmin) of these maps makes it possible to directly reconstruct the lensing potential using only information at larger angular scales (${\ell }\leqslant 700$). From the auto-spectrum of the reconstructed potential, we measure an amplitude of the spectrum to be ${A}_{{\rm{L}}}^{\phi \phi }=1.15\pm 0.36$ (Planck ΛCDM prediction corresponds to ${A}_{{\rm{L}}}^{\phi \phi }=1$) and reject the no-lensing hypothesis at $5.8\sigma $, which is the highest significance achieved to date using an EB lensing estimator. Taking the cross-spectrum of the reconstructed potential with the Planck 2015 lensing map yields ${A}_{{\rm{L}}}^{\phi \phi }=1.13\pm 0.20$. These direct measurements of ${A}_{{\rm{L}}}^{\phi \phi }$ are consistent with the ΛCDM cosmology and with that derived from the previously reported BK14 B-mode auto-spectrum (${A}_{{\rm{L}}}^{\mathrm{BB}}=1.20\pm 0.17$). We perform a series of null tests and consistency checks to show that these results are robust against systematics and are insensitive to analysis choices. These results unambiguously demonstrate that the B modes previously reported by BICEP/Keck at intermediate angular scales ($150\lesssim {\ell }\lesssim 350$) are dominated by gravitational lensing. The good agreement between the lensing amplitudes obtained from the lensing reconstruction and B-mode spectrum starts to place constraints on any alternative cosmological sources of B modes at these angular scales.
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    BICEP3 focal plane design and detector performance
    (SPIE, 2016) Hui, H.; Ade, P. A. R.; Ahmed, Z.; Alexander, Kate; Amiri, M.; Barkats, Denis; Benton, S. J.; Bischoff, Colin; Bock, J. J.; Boenish, H.; Bowens-Rubin, Rachel; Buder, I; Bullock, E.; Buza, Victor; Connors, Jake Anthony; Filippini, J. P.; Fliescher, S.; Grayson, J. A.; Halpern, M.; Harrison, Sarah; Hilton, G. C.; Hristov, V. V.; Irwin, K. D.; Kang, J.; Karkare, Kirit Sukrit; Karpel, E.; Kefeli, S.; Kernasovskiy, S. A.; Kovac, John; Kuo, C. L.; Leitch, E. M.; Lueker, M.; Megerian, K. G.; Monticue, V.; Namikawa, T.; Netterfield, C. B.; Nguyen, H. T.; O, R.; Ogburn, R. W.; Pryke, C; Reintsema, C. D.; Richter, Sonja Valeska; Schwarz, R.; Sorensen, C.; Sheehy, C. D.; Staniszewski, Z. K.; Steinbach, B.; Teply, G. P.; Thompson, K. L.; Tolan, J. E.; Tucker, C.; Turner, A. D.; Vieregg, A. G.; Wandui, A.; Weber, A. C.; Wiebe, D. V.; Willmert, J.; Wu, W. L. K.; Yoon, K. W.
    BICEP3, the latest telescope in the BICEP/Keck program, started science observations in March 2016. It is a 550mm aperture refractive telescope observing the polarization of the cosmic microwave background at 95 GHz. We show the focal plane design and detector performance, including spectral response, optical efficiency and preliminary sensitivity of the upgraded BICEP3. We demonstrate 9.72 µK√s noise performance of the BICEP3 receiver.
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    BICEP3 performance overview and planned Keck Array upgrade
    (2016) Grayson, J. A.; Ade, P. A. R.; Ahmed, Z.; Alexander, Kate; Amiri, M.; Barkats, Denis; Benton, S. J.; Bischoff, Colin; Bock, J. J.; Boenish, H.; Bowens-Rubin, Rachel; Buder, I; Bullock, E.; Buza, Victor; Connors, Jake Anthony; Filippini, J. P.; Fliescher, S.; Halpern, M.; Harrison, Sarah; Hilton, G. C.; Hristov, V. V.; Hui, H.; Irwin, K. D.; Kang, J.; Karkare, Kirit Sukrit; Karpel, E.; Kefeli, S.; Kernasovskiy, S. A.; Kovac, John; Kuo, C. L.; Leitch, E. M.; Lueker, M.; Megerian, K. G.; Monticue, V.; Namikawa, T.; Netterfield, C. B.; Nguyen, H. T.; O, R.; Ogburn, R. W.; Pryke, C; Reintsema, C. D.; Richter, Sonja Valeska; Schwarz, R.; Sorenson, C.; Sheehy, C. D.; Staniszewski, Z. K.; Steinbach, B.; Teply, G. P.; Thompson, K. L.; Tolan, J. E.; Tucker, C.; Turner, A. D.; Vieregg, A. G.; Wandui, A.; Weber, A. C.; Wiebe, D. V.; Willmert, J.; Wu, W. L. K.; Yoon, K. W.
    Bicep3 is a 520 mm aperture, compact two-lens refractor designed to observe the polarization of the cosmic microwave background (CMB) at 95 GHz. Its focal plane consists of modularized tiles of antenna-coupled transition edge sensors (TESs), similar to those used in Bicep2 and the Keck Array. The increased per-receiver optical throughput compared to Bicep2/Keck Array, due to both its faster f /1.7 optics and the larger aperture, more than doubles the combined mapping speed of the Bicep/Keck program. The Bicep3 receiver was recently upgraded to a full complement of 20 tiles of detectors (2560 TESs) and is now beginning its second year of observation (and first science season) at the South Pole. We report on its current performance and observing plans. Given its high per-receiver throughput while maintaining the advantages of a compact design, Bicep3class receivers are ideally suited as building blocks for a 3rd-generation CMB experiment, consisting of multiple receivers spanning 35 GHz to 270 GHz with total detector count in the tens of thousands. We present plans for such an array, the new “Bicep Array” that will replace the Keck Array at the South Pole, including design optimization, frequency coverage, and deployment/observing strategies.
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    Optical characterization of the BICEP3 CMB polarimeter at the South Pole
    (2016) Karkare, Kirit Sukrit; Ade, P. A. R.; Ahmed, Z.; Alexander, Kate; Amiri, M.; Barkats, Denis; Benton, S. J.; Bischoff, Colin; Bock, J. J.; Boenish, H.; Bowens-Rubin, Rachel; Buder, I; Bullock, E.; Buza, Victor; Connors, Jake Anthony; Filippini, J. P.; Fliescher, S. T.; Grayson, J. A.; Halpern, M.; Harrison, Sarah; Hilton, G. C.; Hristov, V. V.; Hui, H.; Irwin, K. D.; Kang, J. H.; Karpel, E.; Kefeli, S.; Kernasovskiy, S. A.; Kovac, John; Kuo, C. L.; Leitch, E. M.; Lueker, M.; Megerian, K. G.; Monticue, V.; Namikawa, T.; Netterfield, C. B.; Nguyen, H. T.; O, R.; Ogburn, R. W.; Pryke, C; Reintsema, C. D.; Richter, Sonja Valeska; St. Germaine, Tyler; Schwarz, R.; Sheehy, C. D.; Staniszewski, Z. K.; Steinbach, B.; Teply, G. P.; Thompson, K. L.; Tolan, J. E.; Tucker, C.; Turner, A. D.; Vieregg, A. G.; Wandui, A.; Weber, A.; Willmert, J.; Wong, C; Wu, W. L. K.; Yoon, K. W.
    Bicep3 is a small-aperture refracting cosmic microwave background (CMB) telescope designed to make sensitive polarization maps in pursuit of a potential B-mode signal from inflationary gravitational waves. It is the latest in the Bicep/Keck Array series of CMB experiments located at the South Pole, which has provided the most stringent constraints on inflation to date. For the 2016 observing season, Bicep3 was outfitted with a full suite of 2400 optically coupled detectors operating at 95 GHz. In these proceedings we report on the far field beam performance using calibration data taken during the 2015-2016 summer deployment season in situ with a thermal chopped source. We generate high-fidelity per-detector beam maps, show the array-averaged beam profile, and characterize the differential beam response between co-located, orthogonally polarized detectors which contributes to the leading instrumental systematic in pair differencing experiments. We find that the levels of differential pointing, beamwidth, and ellipticity are similar to or lower than those measured for Bicep2 and Keck Array. The magnitude and distribution of Bicep3’s differential beam mismatch – and the level to which temperature-to-polarization leakage may be marginalized over or subtracted in analysis – will inform the design of next-generation CMB experiments with many thousands of detectors.