Lungu, Marius, Storer, Emilie R., Hasselfield, Matthew, Duivenvoorden, Adriaan J., Calabrese, Erminia ![]() |
Abstract
We describe the measurement and treatment of the telescope beams for the Atacama Cosmology Telescope's fourth data release, DR4. Observations of Uranus are used to measure the central portion (<12') of the beams to roughly -40 dB of the peak. Such planet maps in intensity are used to construct azimuthally averaged beam profiles, which are fit with a physically motivated model before being transformed into Fourier space. We investigate and quantify a number of percent-level corrections to the beams, all of which are important for precision cosmology. Uranus maps in polarization are used to measure the temperature-to-polarization leakage in the main part of the beams, which is ≲ 1% (2.5%) at 150 GHz (98 GHz). The beams also have polarized sidelobes, which are measured with observations of Saturn and deprojected from the ACT time-ordered data. Notable changes relative to past ACT beam analyses include an improved subtraction of the atmospheric effects from Uranus calibration maps, incorporation of a scattering term in the beam profile model, and refinements to the beam model uncertainties and the main temperature-to-polarization leakage terms in the ACT power spectrum analysis.
Item Type: | Article |
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Date Type: | Publication |
Status: | Published |
Schools: | Advanced Research Computing @ Cardiff (ARCCA) Physics and Astronomy |
Publisher: | IOP Publishing |
ISSN: | 1475-7516 |
Date of First Compliant Deposit: | 15 July 2022 |
Date of Acceptance: | 17 March 2022 |
Last Modified: | 17 Jun 2024 14:50 |
URI: | https://orca.cardiff.ac.uk/id/eprint/151331 |
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