The Atacama Cosmology Telescope: Measurement and Analysis of 1D Beams for DR4

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.

32 pages, 21 figures

References in corpus (10)

• The Atacama Cosmology Telescope: DR4 Maps and Cosmological Parameters
• The Atacama Cosmology Telescope: A Measurement of the Cosmic Microwave Background Power Spectra at 98 and 150 GHz
• Measurements of the E-Mode Polarization and Temperature-E-Mode Correlation of the CMB from SPT-3G 2018 Data
• Optical Design of the Atacama Cosmology Telescope and the Millimeter Bolometric Array Camera
• The Atacama Cosmology Telescope: A CMB lensing mass map over 2100 square degrees of sky and its cross-correlation with BOSS-CMASS galaxies
• The Atacama Cosmology Telescope: DR5 maps of 18,000 square degrees of the microwave sky from ACT 2008-2018 data
• The Atacama Cosmology Telescope: Constraints on Cosmic Birefringence
• Shrinkage Estimation of the Power Spectrum Covariance Matrix
• The Atacama Cosmology Telescope: Summary of DR4 and DR5 Data Products and Data Access
• The Atacama Cosmology Telescope: Modeling Bulk Atmospheric Motion

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• The Atacama Cosmology Telescope: A Measurement of the DR6 CMB Lensing Power Spectrum and its Implications for Structure Growth
• The conceptual design of the 50-meter Atacama Large Aperture Submillimeter Telescope (AtLAST)
• Cosmology Large Angular Scale Surveyor (CLASS): 90 GHz Telescope Pointing, Beam Profile, Window Function, and Polarization Performance
• The Atacama Cosmology Telescope: Flux Upper Limits from a Targeted Search for Extragalactic Transients
• Atacama Large Aperture Submillimeter Telescope (AtLAST) Science: Resolving the Hot and Ionized Universe through the Sunyaev-Zeldovich effect
• PROTOCALC, A W-band polarized calibrator for CMB Telescopes: application to Simons Observatory and CLASS
• The Simons Observatory: Beam characterization for the Small Aperture Telescopes
• Disentangling the Halo: Joint Model for Measurements of the Kinetic Sunyaev-Zeldovich Effect and Galaxy-Galaxy Lensing
• Modeling optical systematics for the Taurus CMB experiment
• The Simons Observatory: Quantifying the impact of beam chromaticity on large-scale B-mode science
• Purely quadratic non-Gaussianity from tachyonic instability: Primordial black holes and scalar-induced gravitational waves