The Atacama Cosmology Telescope: Delensed Power Spectra and Parameters

28 Jul 2020  ·  Dongwon Han, Neelima Sehgal, Amanda MacInnis, Alexander van Engelen, Blake D. Sherwin, Mathew S. Madhavacheril, Simone Aiola, Nicholas Battaglia, James A. Beall, Daniel T. Becker, Erminia Calabrese, Steve K. Choi, Omar Darwish, Edward V. Denison, Jo Dunkley, Simone Ferraro, Anna E. Fox, Matthew Hasselfield, J. Colin Hill, Gene C. Hilton, Matt Hilton, Renée Hložek, Johannes Hubmayr, John P. Hughes, Arthur Kosowsky, Jeff Van Lanen, Thibaut Louis, Kavilan Moodley, Sigurd Naess, Toshiya Namikawa, Federico Nati, John P. Nibarger, Michael D. Niemack, Lyman A. Page, Bruce Partridge, Frank J. Qu, Alessandro Schillaci, David N. Spergel, Suzanne Staggs, Emilie Storer, Edward J. Wollack ·

We present LCDM cosmological parameter constraints obtained from delensed microwave background power spectra. Lensing maps from a subset of DR4 data from the Atacama Cosmology Telescope (ACT) are used to undo the lensing effect in ACT spectra observed at 150 and 98 GHz. At 150 GHz, we remove the lensing distortion with an effective efficiency of 30% (TT), 30% (EE), 26% (TE) and 20% (BB); this results in detections of the delensing effect at 8.7 sigma (TT), 5.1 sigma (EE), 2.6 sigma (TE), and 2.4 sigma (BB) significance. The combination of 150 and 98 GHz TT, EE, and TE delensed spectra is well fit by a standard LCDM model. We also measure the shift in best-fit parameters when fitting delensed versus lensed spectra; while this shift does not inform our ability to measure cosmological parameters, it does provide a three-way consistency check among the lensing inferred from the best-fit parameters, the lensing in the CMB power spectrum, and the reconstructed lensing map. This shift is predicted to be zero when fitting with the correct model since both lensed and delensed spectra originate from the same region of sky. Fitting with a LCDM model and marginalizing over foregrounds, we find that the shift in cosmological parameters is consistent with zero. Our results show that gravitational lensing of the microwave background is internally consistent within the framework of the standard cosmological model.

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Cosmology and Nongalactic Astrophysics High Energy Physics - Phenomenology