Browsing by Author "Coulton, William R."

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    Non-gaussianity of secondary anisotropies from ACTPol and Planck
    (2018) Coulton, William R.; Aiola, Simone; Battaglia, Nicholas; Calabrese, Erminia; Choi, Steve K.; Devlin, Mark J.; Gallardo, Patricio A.; Colin Hill, J.; Hincks, Adam D.; Maurin, Loïc Benjamin
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    The Atacama Cosmology Telescope: map-based noise simulations for DR6
    (2023) Atkins, Zachary; Duivenvoorden, Adriaan J.; Coulton, William R.; Qu, Frank J.; Aiola, Simone; Calabrese, Erminia; Chesmore, Grace E.; Choi, Steve K.; Devlin, Mark J.; Dunkley, Jo; Hervias-Caimapo, Carlos; Guan, Yilun; La Posta, Adrien; Li, Zack; Louis, Thibaut; Madhavacheril, Mathew S.; Moodleyno, Kavilan; Naess, Sigurd; Nati, Federico; Niemack, Michael D.; Page, Lyman; Puddu, Roberto; Salatino, Maria; Sifon, Cristobal; Staggs, Suzanne T.; Vargasj, Cristian; Vavagiakis, Eve M.; Wollack, Edward J.
    The increasing statistical power of cosmic microwave background (CMB) datasets requires a commensurate effort in understanding their noise properties. The noise in maps from ground-based instruments is dominated by large-scale correlations, which poses a modeling challenge. This paper develops novel models of the complex noise covariance structure in the Atacama Cosmology Telescope Data Release 6 (ACT DR6) maps. We first enumerate the noise properties that arise from the combination of the atmosphere and the ACT scan strategy. We then prescribe a class of Gaussian, map-based noise models, including a new wavelet-based approach that uses directional wavelet kernels for modeling correlated instrumental noise. The models are empirical, whose only inputs are a small number of independent realizations of the same region of sky. We evaluate the performance of these models against the ACT DR6 data by drawing ensembles of noise realizations. Applying these simulations to the ACT DR6 power spectrum pipeline reveals a similar to 20% excess in the covariance matrix diagonal when compared to an analytic expression that assumes noise properties are uniquely described by their power spectrum. Along with our public code, mnms, this work establishes a necessary element in the science pipelines of both ACT DR6 and future ground-based CMB experiments such as the Simons Observatory (SO).
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    The Atacama Cosmology Telescope: Mitigating the Impact of Extragalactic Foregrounds for the DR6 Cosmic Microwave Background Lensing Analysis
    (2024) MacCrann, Niall; Sherwin, Blake D.; Qu, Frank J.; Namikawa, Toshiya; Madhavacheril, Mathew S.; Abril-Cabezas, Irene; An, Rui; Austermann, Jason E.; Battaglia, Nicholas; Battistelli, Elia S.; Beall, James A.; Bolliet, Boris; Bond, J. Richard; Cai, Hongbo; Calabrese, Erminia; Coulton, William R.; Darwish, Omar; Duff, Shannon M.; Duivenvoorden, Adriaan J.; Dunkley, Jo; Farren, Gerrit S.; Ferraro, Simone; Golec, Joseph E.; Guan, Yilun; Han, Dongwon; Hervias-Caimapo, Carlos; Hill, J. Colin; Hilton, Matt; Hlozek, Renee; Hubmayr, Johannes; Kim, Joshua; Li, Zack; Kosowsky, Arthur; Louis, Thibaut; McMahon, Jeff; A. Marques, Gabriela; Moodley, Kavilan; Naess, Sigurd; Niemack, Michael D.; Page, Lyman; Partridge, Bruce; Schaan, Emmanuel; Sehgal, Neelima; Sifon, Cristobal; Wollack, Edward J.; Salatino, Maria; Ullom, Joel N.; Van Lanen, Jeff; Van Engelen, Alexander; Wenzl, Lukas
    We investigate the impact and mitigation of extragalactic foregrounds for the cosmic microwave background (CMB) lensing power spectrum analysis of Atacama Cosmology Telescope (ACT) data release 6 (DR6) data. Two independent microwave sky simulations are used to test a range of mitigation strategies. We demonstrate that finding and then subtracting point sources, finding and then subtracting models of clusters, and using a profile bias-hardened lensing estimator together reduce the fractional biases to well below statistical uncertainties, with the inferred lensing amplitude, A lens, biased by less than 0.2 sigma. We also show that another method where a model for the cosmic infrared background (CIB) contribution is deprojected and high-frequency data from Planck is included has similar performance. Other frequency-cleaned options do not perform as well, either incurring a large noise cost or resulting in biased recovery of the lensing spectrum. In addition to these simulation-based tests, we also present null tests on the ACT DR6 data for sensitivity of our lensing spectrum estimation to differences in foreground levels between the two ACT frequencies used, while nulling the CMB lensing signal. These tests pass whether the nulling is performed at the map or bandpower level. The CIB-deprojected measurement performed on the DR6 data is consistent with our baseline measurement, implying that contamination from the CIB is unlikely to significantly bias the DR6 lensing spectrum. This collection of tests gives confidence that the ACT DR6 lensing measurements and cosmological constraints presented in companion papers to this work are robust to extragalactic foregrounds.