The Atacama Cosmology Telescope: measurement and analysis of 1D beams for DR4. Issue 5 (1st May 2022)

• Record Type: Journal Article
• Authors: Lungu, Marius; Storer, Emilie R.; Hasselfield, Matthew; Duivenvoorden, Adriaan J.; Calabrese, Erminia; Chesmore, Grace E.; Choi, Steve K.; Dunkley, Jo; Dünner, Rolando; Gallardo, Patricio A.; Golec, Joseph E.; Guan, Yilun; Hill, J. Colin; Hincks, Adam D.; Hubmayr, Johannes; Madhavacheril, Mathew S.; Mallaby-Kay, Maya; McMahon, Jeff; Moodley, Kavilan; Naess, Sigurd; Nati, Federico; Niemack, Michael D.; Page, Lyman A.; Partridge, Bruce; Puddu, Roberto; Schillaci, Alessandro; Sifón, Cristóbal; Staggs, Suzanne; Sunder, Dhaneshwar D.; Wollack, Edward J.; Xu, Zhilei;
• Is Part Of: Journal of cosmology and astroparticle physics. Volume 2022:Issue 5(2022)
• Publication Date: 2022-05-01
• Subjects: CMBR detectors -- CMBR experiments; Cosmology -- Periodicals; Astrophysics -- Periodicals; 523.0105
• DOI: 10.1088/1475-7516/2022/05/044
• Languages: English
• ISSNs: 1475-7516

Abstract

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.