Browsing by Author "Namikawa, Toshiya"

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    The Atacama Cosmology Telescope: A Measurement of the DR6 CMB Lensing Power Spectrum and Its Implications for Structure Growth
    (2024) Qu, Frank; Sherwin, Blake D.; Madhavacheril, Mathew S.; Han, Dongwon; Crowley, Kevin T.; Abril-Cabezas, Irene; Ade, Peter A. R.; Aiola, Simone; Alford, Tommy; Amiri, Mandana; Amodeo, Stefania; An, Rui; Atkins, Zachary; Austermann, Jason E.; Battaglia, Nicholas; Battistelli, Elia Stefano; Beall, James A.; Bean, Rachel; Beringue, Benjamin; Bhandarkar, Tanay; Biermann, Emily; Bolliet, Boris; Bond, J. Richard; Cai, Hongbo; Calabrese, Erminia; Calafut, Victoria; Capalbo, Valentina; Carrero, Felipe; Carron, Julien; Challinor, Anthony; Chesmore, Grace E.; Cho, Hsiao-Mei; Choi, Steve K.; Clark, Susan E.; Rosado, Rodrigo Cordova; Cothard, Nicholas F.; Coughlin, Kevin; Coulton, William; Dalal, Roohi; Darwish, Omar; Devlin, Mark J.; Dicker, Simon; Doze, Peter; Duell, Cody J.; Duff, Shannon M.; Duivenvoorden, Adriaan J.; Dunkley, Jo; Dunner, Rolando; Fanfani, Valentina; Fankhanel, Max; Farren, Gerrit; Ferraro, Simone; Freundt, Rodrigo; Fuzia, Brittany; Gallardo, Patricio A.; Garrido, Xavier; Gluscevic, Vera; Golec, Joseph E.; Guan, Yilun; Halpern, Mark; Harrison, Ian; Hasselfield, Matthew; Healy, Erin; Henderson, Shawn; Hensley, Brandon; Hervias-Caimapo, Carlos; Hill, J. Colin; Hilton, Gene C.; Hilton, Matt; Hincks, Adam D.; Hlozek, Renee; Ho, Shuay-Pwu Patty; Huber, Zachary B.; Hubmayr, Johannes; Huffenberger, Kevin M.; Hughes, John P.; Irwin, Kent; Isopi, Giovanni; Jense, Hidde T.; Keller, Ben; Kim, Joshua; Knowles, Kenda; Koopman, Brian J.; Kosowsky, Arthur; Kramer, Darby; Kusiak, Aleksandra; La Posta, Adrien; Lague, Alex; Lakey, Victoria; Lee, Eunseong; Li, Zack; Li, Yaqiong; Limon, Michele; Lokken, Martine; Louis, Thibaut; Lungu, Marius; MacCrann, Niall; MacInnis, Amanda; Maldonado, Diego; Maldonado, Felipe; Mallaby-Kay, Maya; Marques, Gabriela A.; McMahon, Jeff; Mehta, Yogesh; Menanteau, Felipe; Moodley, Kavilan; Morris, Thomas W.; Mroczkowski, Tony; Naess, Sigurd; Namikawa, Toshiya; Nati, Federico; Newburgh, Laura; Nicola, Andrina; Niemack, Michael D.; Nolta, Michael R.; Orlowski-Scherer, John; Page, Lyman A.; Pandey, Shivam; Partridge, Bruce; Prince, Heather; Puddu, Roberto; Radiconi, Federico; Robertson, Naomi; Rojas, Felipe; Sakuma, Tai; Salatino, Maria; Schaan, Emmanuel; Schmitt, Benjamin L.; Sehgal, Neelima; Shaikh, Shabbir; Sierra, Carlos; Sievers, Jon; Sifon, Cristobal; Simon, Sara; Sonka, Rita; Spergel, David N.; Staggs, Suzanne T.; Storer, Emilie; Switzer, Eric R.; Tampier, Niklas; Thornton, Robert; Trac, Hy; Treu, Jesse; Tucker, Carole; Ullom, Joel; Vale, Leila R.; Van Engelen, Alexander; Van Lanen, Jeff; van Marrewijk, Joshiwa; Vargas, Cristian; Vavagiakis, Eve M.; Wagoner, Kasey; Wang, Yuhan; Wenzl, Lukas; Wollack, Edward J.; Xu, Zhilei; Zago, Fernando; Zheng, Kaiwen
    We present new measurements of cosmic microwave background (CMB) lensing over 9400 deg2 of the sky. These lensing measurements are derived from the Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) CMB data set, which consists of five seasons of ACT CMB temperature and polarization observations. We determine the amplitude of the CMB lensing power spectrum at 2.3% precision (43 sigma significance) using a novel pipeline that minimizes sensitivity to foregrounds and to noise properties. To ensure that our results are robust, we analyze an extensive set of null tests, consistency tests, and systematic error estimates and employ a blinded analysis framework. Our CMB lensing power spectrum measurement provides constraints on the amplitude of cosmic structure that do not depend on Planck or galaxy survey data, thus giving independent information about large-scale structure growth and potential tensions in structure measurements. The baseline spectrum is well fit by a lensing amplitude of A lens = 1.013 +/- 0.023 relative to the Planck 2018 CMB power spectra best-fit Lambda CDM model and A lens = 1.005 +/- 0.023 relative to the ACT DR4 + WMAP best-fit model. From our lensing power spectrum measurement, we derive constraints on the parameter combination S8CMBL equivalent to sigma 8 omega m/0.30.25 of S8CMBL=0.818 +/- 0.022 from ACT DR6 CMB lensing alone and S8CMBL=0.813 +/- 0.018 when combining ACT DR6 and Planck NPIPE CMB lensing power spectra. These results are in excellent agreement with Lambda CDM model constraints from Planck or ACT DR4 + WMAP CMB power spectrum measurements. Our lensing measurements from redshifts z similar to 0.5-5 are thus fully consistent with Lambda CDM structure growth predictions based on CMB anisotropies probing primarily z similar to 1100. We find no evidence for a suppression of the amplitude of cosmic structure at low redshifts.
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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.
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    The Simons Observatory: Combining cross-spectral foreground cleaning with multitracer B- mode delensing for improved constraints on inflation
    (2024) Hertig, Emilie; Wolz, Kevin; Namikawa, Toshiya; Lizancos, Anton Baleato; Azzoni, Susanna; Abril-Cabezas, Irene; Alonso, David; Baccigalupi, Carlo; Calabrese, Erminia; Challinor, Anthony; Errard, Josquin; Fabbian, Giulio; Hervias-Caimapo, Carlos; Jost, Baptiste; Krachmalnicoff, Nicoletta; Lonappan, Anto I.; Morshed, Magdy; Pagano, Luca; Sherwin, Blake
    The Simons Observatory (SO), due to start full science operations in early 2025, aims to set tight constraints on inflationary physics by inferring the tensor-to-scalar ratio r from measurements of cosmic microwave background (CMB) polarization B-modes. Its nominal design including three small-aperture telescopes (SATs) targets a precision sigma(r ( r 1 / 4 0) ) <= 0.003 without delensing. Achieving this goal and further reducing uncertainties requires a thorough understanding and mitigation of other large-scale B-mode sources such as Galactic foregrounds and weak gravitational lensing. We present an analysis pipeline aiming to estimate r by including delensing within a cross-spectral likelihood, and demonstrate it for the first time on SO-like simulations accounting for various levels of foreground complexity, inhomogeneous noise and partial sky coverage. As introduced in an earlier SO delensing paper, lensing Bmodes are synthesized using internal CMB lensing reconstructions as well as Planck-like cosmic infrared background maps and LSST-like galaxy density maps. We then extend SO's power-spectrum-based foreground- cleaning algorithm to include all auto- and cross-spectra between the lensing template and the SAT Bmodes in the likelihood function. This allows us to constrain r and the parameters of our foreground model simultaneously. Within this framework, we demonstrate the equivalence of map-based and cross-spectral delensing and use it to motivate an optimized pixel-weighting scheme for power spectrum estimation. We start by validating our pipeline in the simplistic case of uniform foreground spectral energy distributions. In the absence of primordial Bmodes, we find that the 16 statistical uncertainty on r, 6(r), ( r ) , decreases by 37% as a result of delensing. Tensor modes at the level of r 1 / 4 0.01 are successfully detected by our pipeline. Even when using more realistic foreground models including spatial variations in the dust and synchrotron spectral properties, we obtain unbiased estimates of r both with and without delensing by employing the moment-expansion method. In this case, uncertainties are increased due to the higher number of model parameters, and delensing-related improvements range between 27% and 31%. These results constitute the first realistic assessment of the delensing performance at SO's nominal sensitivity level.