Browsing by Author "Farren, Gerrit S."

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    The Atacama Cosmology Telescope: Cosmology from Cross-correlations of unWISE Galaxies and ACT DR6 CMB Lensing
    (2024) Farren, Gerrit S.; Krolewski, Alex; MacCrann, Niall; Ferraro, Simone; Abril-Cabezas, Irene; An, Rui; Atkins, Zachary; Battaglia, Nicholas; Bond, J. Richard; Calabrese, Erminia; Choi, Steve K.; Darwish, Omar; Devlin, Mark J.; Duivenvoorden, Adriaan J.; Dunkley, Jo; Hill, J. Colin; Hilton, Matt; Huffenberger, Kevin M.; Kim, Joshua; Louis, Thibaut; Madhavacheril, Mathew S.; Marques, Gabriela A.; McMahon, Jeff; Moodley, Kavilan; Page, Lyman A.; Partridge, Bruce; Qu, Frank J.; Schaan, Emmanuel; Sehgal, Neelima; Sherwin, Blake D.; Sifon, Cristobal; Staggs, Suzanne T.; Van Engelen, Alexander; Vargas, Cristian; Wenzl, Lukas; White, Martin; Wollack, Edward J.
    We present tomographic measurements of structure growth using cross-correlations of Atacama Cosmology Telescope (ACT) DR6 and Planck cosmic microwave background (CMB) lensing maps with the unWISE Blue and Green galaxy samples, which span the redshift ranges 0.2 less than or similar to z less than or similar to 1.1 and 0.3 less than or similar to z less than or similar to 1.8, respectively. We improve on prior unWISE cross-correlations not just by making use of the new, high-precision ACT DR6 lensing maps, but also by including additional spectroscopic data for redshift calibration and by analyzing our measurements with a more flexible theoretical model. We determine the amplitude of matter fluctuations at low redshifts (z similar or equal to 0.2-1.6), finding S 8 equivalent to sigma 8 ( Omega m / 0.3 ) 0.5 = 0.813 +/- 0.021 using the ACT cross-correlation alone and S 8 = 0.810 +/- 0.015 with a combination of Planck and ACT cross-correlations; these measurements are fully consistent with the predictions from primary CMB measurements assuming standard structure growth. The addition of baryon acoustic oscillation data breaks the degeneracy between sigma 8 and Omega m , allowing us to measure sigma 8 = 0.813 +/- 0.020 from the cross-correlation of unWISE with ACT and sigma 8 = 0.813 +/- 0.015 from the combination of cross-correlations with ACT and Planck. These results also agree with the expectations from primary CMB extrapolations in Lambda CDM cosmology; the consistency of sigma 8 derived from our two redshift samples at z similar to 0.6 and 1.1 provides a further check of our cosmological model. Our results suggest that structure formation on linear scales is well described by Lambda CDM even down to low redshifts z less than or similar to 1.
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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.