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The Fred Young Submillimeter Telescope (FYST), which is the telescope of the CCAT-prime project, will be located at 5600 m near the summit of Cerro Chajnantor in northern Chile, and will host the modular instrument called Prime-Cam. Two of the instrument modules in Prime-Cam will be a spectrometer with a resolving power of R ∼ 100 and populated with a detector array of several thousand KIDs (Kinetic Inductance Detectors). The main science goal of this spectrometer module, called EoR-Spec, is to probe the Epoch of Reionization (EoR) in the early universe using the Line Intensity Mapping (LIM) technique with the redshifted [CII] fine-structure line. This presentation provides an overview of the optical, mechanical, and spectral design of EoR-Spec, as well as of the detector array that will be used. The optical design consists of four silicon lenses that have anti-reflection metamaterial layers. A scanning Fabry-Perot Interferometer (FPI) will be located at the pupil and provides the spectral resolution over the full spectral coverage of 210 GHz to 420 GHz in two orders, resulting in a redshift coverage of the [CII] line from z = 3.5 to z = 8. The detector array consists of three subarrays of KIDs, two of which are tuned for the frequency range between 210 GHz and 315 GHz, and one that is tuned for the 315 GHz to 420 GHz range. The angular resolution will be between about 30'' to 50''. This presentation also addresses the spectral and spatial scanning strategy of EoR-Spec on FYST. EoR-Spec is expected to be installed into Prime-Cam about 1 year after first light of FYST. 

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. 

ABSTRACT Compact sources can cause scatter in the scaling relationships between the amplitude of the thermal Sunyaev–Zel’dovich Effect (tSZE) in galaxy clusters and cluster mass. Estimates of the importance of this scatter vary – largely due to limited data on sources in clusters at the frequencies at which tSZE cluster surveys operate. In this paper, we present 90 GHz compact source measurements from a sample of 30 clusters observed using the MUSTANG2 instrument on the Green Bank Telescope. We present simulations of how a source’s flux density, spectral index, and angular separation from the cluster’s centre affect the measured tSZE in clusters detected by the Atacama Cosmology Telescope (ACT). By comparing the MUSTANG2 measurements with these simulations we calibrate an empirical relationship between 1.4 GHz flux densities from radio surveys and source contamination in ACT tSZE measurements. We find 3 per cent of the ACT clusters have more than a 20 per cent decrease in Compton-y but another 3 per cent have a 10 per cent increase in the Compton-y due to the matched filters used to find clusters. As sources affect the measured tSZE signal and hence the likelihood that a cluster will be detected, testing the level of source contamination in the tSZE signal using a tSZE-selected catalogue is inherently biased. We confirm this by comparing the ACT tSZE catalogue with optically and X-ray-selected cluster catalogues. There is a strong case for a large, high-resolution survey of clusters to better characterize their source population.