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    Optimal Cosmic Microwave Background Lensing Reconstruction and Parameter Estimation with SPTpol Data
    Millea, M ; Daley, CM ; Chou, T-L ; Anderes, E ; Ade, PAR ; Anderson, AJ ; Austermann, JE ; Avva, JS ; Beall, JA ; Bender, AN ; Benson, BA ; Bianchini, F ; Bleem, LE ; Carlstrom, JE ; Chang, CL ; Chaubal, P ; Chiang, HC ; Citron, R ; Moran, CC ; Crawford, TM ; Crites, AT ; de Haan, T ; Dobbs, MA ; Everett, W ; Gallicchio, J ; George, EM ; Goeckner-Wald, N ; Guns, S ; Gupta, N ; Halverson, NW ; Henning, JW ; Hilton, GC ; Holder, GP ; Holzapfel, WL ; Hrubes, JD ; Huang, N ; Hubmayr, J ; Irwin, KD ; Knox, L ; Lee, AT ; Li, D ; Lowitz, A ; McMahon, JJ ; Meyer, SS ; Mocanu, LM ; Montgomery, J ; Natoli, T ; Nibarger, JP ; Noble, G ; Novosad, V ; Omori, Y ; Padin, S ; Patil, S ; Pryke, C ; Reichardt, CL ; Ruhl, JE ; Saliwanchik, BR ; Schaffer, KK ; Sievers, C ; Smecher, G ; Stark, AA ; Thorne, B ; Tucker, C ; Veach, T ; Vieira, JD ; Wang, G ; Whitehorn, N ; Wu, WLK ; Yefremenko, V (American Astronomical Society, 2021-12-01)
    We perform the first simultaneous Bayesian parameter inference and optimal reconstruction of the gravitational lensing of the cosmic microwave background (CMB), using 100 deg2 of polarization observations from the SPTpol receiver on the South Pole Telescope. These data reach noise levels as low as 5.8 µK arcmin in polarization, which are low enough that the typically used quadratic estimator (QE) technique for analyzing CMB lensing is significantly suboptimal. Conversely, the Bayesian procedure extracts all lensing information from the data and is optimal at any noise level. We infer the amplitude of the gravitational lensing potential to be A f =0.949\,\pm \,0.122 using the Bayesian pipeline, consistent with our QE pipeline result, but with 17% smaller error bars. The Bayesian analysis also provides a simple way to account for systematic uncertainties, performing a similar job as frequentist "bias hardening"or linear bias correction, and reducing the systematic uncertainty on A f due to polarization calibration from almost half of the statistical error to effectively zero. Finally, we jointly constrain A f along with A L, the amplitude of lensing-like effects on the CMB power spectra, demonstrating that the Bayesian method can be used to easily infer parameters both from an optimal lensing reconstruction and from the delensed CMB, while exactly accounting for the correlation between the two. These results demonstrate the feasibility of the Bayesian approach on real data, and pave the way for future analysis of deep CMB polarization measurements with SPT-3G, Simons Observatory, and CMB-S4, where improvements relative to the QE can reach 1.5 times tighter constraints on A f and seven times lower effective lensing reconstruction noise.
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    Suppressing the Thermal SZ-induced Variance in CMB-cluster Lensing Estimators
    Patil, S ; Raghunathan, S ; Reichardt, CL (American Astronomical Society, 2020-01-01)
    Accurate galaxy cluster mass measurements from the gravitational lensing of the cosmic microwave background temperature maps depend on mitigating potential biases from the cluster's own thermal Sunyaev–Zel'dovich (SZ) effect signal. Quadratic lensing estimators use a pair of maps to extract the lensing signal: a large-scale gradient map and a small-scale lensing map. The SZ bias can be eliminated by using an SZ-free map in the pair, with the gradient map being favored for signal-to-noise reasons. However, while this approach eliminates the bias, the SZ power in small-scale lensing map adds extra variance that can become significant for high-mass clusters and low-noise surveys. In this work, we propose projecting out an SZ template to reduce the SZ variance. Any residual SZ signal after template fitting is uncorrelated with the SZ-free gradient map, and thus does not bias the mass measurements. For massive clusters above $4\times {10}^{14}$ ${M}_{\odot }$ observed by the upcoming CMB-S4 and Simons Observatory experiments, we find that the template fitting approach would increase the cluster lensing signal-to-noise by a factor of 1.4.
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    Constraints on Cosmological Parameters from the 500 deg(2) SPTPOL Lensing Power Spectrum
    Bianchini, F ; Wu, WLK ; Ade, PAR ; Anderson, AJ ; Austermann, JE ; Avva, JS ; Beall, JA ; Bender, AN ; Benson, BA ; Bleem, LE ; Carlstrom, JE ; Chang, CL ; Chaubal, P ; Chiang, HC ; Citron, R ; Moran, CC ; Crawford, TM ; Crites, AT ; de Haan, T ; Dobbs, MA ; Everett, W ; Gallicchio, J ; George, EM ; Gilbert, A ; Gupta, N ; Halverson, NW ; Harrington, N ; Henning, JW ; Hilton, GC ; Holder, GP ; Holzapfel, WL ; Hrubes, JD ; Huang, N ; Hubmayr, J ; Irwin, KD ; Knox, L ; Lee, AT ; Li, D ; Lowitz, A ; Manzotti, A ; McMahon, JJ ; Meyer, SS ; Millea, M ; Mocanu, LM ; Montgomery, J ; Nadolski, A ; Natoli, T ; Nibarger, JP ; Noble, G ; Novosad, V ; Omori, Y ; Padin, S ; Patil, S ; Pryke, C ; Reichardt, CL ; Ruhl, JE ; Saliwanchik, BR ; Sayre, JT ; Schaffer, KK ; Sievers, C ; Simard, G ; Smecher, G ; Stark, AA ; Story, KT ; Tucker, C ; Vanderlinde, K ; Veach, T ; Vieira, JD ; Wang, G ; Whitehorn, N ; Yefremenko, V (American Astronomical Society, 2020-01-16)
    We present cosmological constraints based on the cosmic microwave background (CMB) lensing potential power spectrum measurement from the recent 500 deg2 SPTpol survey, the most precise CMB lensing measurement from the ground to date. We fit a flat ΛCDM model to the reconstructed lensing power spectrum alone and in addition with other data sets: baryon acoustic oscillations (BAO), as well as primary CMB spectra from Planck and SPTpol. The cosmological constraints based on SPTpol and Planck lensing band powers are in good agreement when analyzed alone and in combination with Planck full-sky primary CMB data. With weak priors on the baryon density and other parameters, the SPTpol CMB lensing data alone provide a 4% constraint on ${\sigma }_{8}{{\rm{\Omega }}}_{m}^{0.25}=0.593\pm 0.025$. Jointly fitting with BAO data, we find ${\sigma }_{8}=0.779\pm 0.023$, ${{\rm{\Omega }}}_{m}={0.368}_{-0.037}^{+0.032}$, and ${H}_{0}={72.0}_{-2.5}^{+2.1}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$, up to $2\sigma $ away from the central values preferred by Planck lensing + BAO. However, we recover good agreement between SPTpol and Planck when restricting the analysis to similar scales. We also consider single-parameter extensions to the flat ΛCDM model. The SPTpol lensing spectrum constrains the spatial curvature to be ${{\rm{\Omega }}}_{K}=-0.0007\pm 0.0025$ and the sum of the neutrino masses to be $\sum {m}_{\nu }\lt 0.23$ eV at 95% C.L. (with Planck primary CMB and BAO data), in good agreement with the Planck lensing results. With the differences in the signal-to-noise ratio of the lensing modes and the angular scales covered in the lensing spectra, this analysis represents an important independent check on the full-sky Planck lensing measurement.