The Atacama Cosmology Telescope: Mitigating the Impact of Extragalactic Foregrounds for the DR6 Cosmic Microwave Background Lensing Analysis

Journal Article · 30 April 2024 · The Astrophysical Journal

DOI: https://doi.org/10.3847/1538-4357/ad2610 · OSTI ID:1973631

MacCrann, Niall  ^[1]; 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; Hervías-Caimapo, Carlos; Hill, J. Colin; Hilton, Matt ; Hložek, Renée; 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 ; Sifón, Cristóbal; Wollack, Edward J. ; Salatino, Maria; Ullom, Joel N.; Van Lanen, Jeff; Van Engelen, Alexander; Wenzl, Lukas

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1. University of Cambridge (United Kingdom); Kavli Institute for Cosmology Cambridge (United Kingdom); ACT Collaboration. et al.

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 0.2σ. 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.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP)
• Contributing Organization: ACT Collaboration
• Grant/Contract Number: AC02-07CH11359; AC02-76SF00515
• OSTI ID: 1973631
• Report Number(s): FERMILAB-PUB--23-236-PPD; arXiv:2304.05196; oai:inspirehep.net:2650561; oai:inspirehep.net:2650561
• Journal Information: The Astrophysical Journal, Journal Name: The Astrophysical Journal Journal Issue: 1 Vol. 966; ISSN 0004-637X
• Publisher: IOP PublishingCopyright Statement
• Country of Publication: United States
• Language: English