19 research outputs found
The Atacama Cosmology Telescope: A Catalog of >4000 SunyaevâZelâdovich Galaxy Clusters
We present a catalog of 4195 optically confirmed SunyaevâZel'dovich (SZ) selected galaxy clusters detected with signal-to-noise ratio >4 in 13,211 deg2 of sky surveyed by the Atacama Cosmology Telescope (ACT). Cluster candidates were selected by applying a multifrequency matched filter to 98 and 150 GHz maps constructed from ACT observations obtained from 2008 to 2018 and confirmed using deep, wide-area optical surveys. The clusters span the redshift range 0.04 1 clusters, and a total of 868 systems are new discoveries. Assuming an SZ signal versus mass-scaling relation calibrated from X-ray observations, the sample has a 90% completeness mass limit of M500c > 3.8 Ă 1014 Mâ, evaluated at z = 0.5, for clusters detected at signal-to-noise ratio >5 in maps filtered at an angular scale of 2farcm4. The survey has a large overlap with deep optical weak-lensing surveys that are being used to calibrate the SZ signal mass-scaling relation, such as the Dark Energy Survey (4566 deg2), the Hyper Suprime-Cam Subaru Strategic Program (469 deg2), and the Kilo Degree Survey (825 deg2). We highlight some noteworthy objects in the sample, including potentially projected systems, clusters with strong lensing features, clusters with active central galaxies or star formation, and systems of multiple clusters that may be physically associated. The cluster catalog will be a useful resource for future cosmological analyses and studying the evolution of the intracluster medium and galaxies in massive clusters over the past 10 Gyr
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SAMDI's research report on the Community Development Workers' Programme
Commissioned by the South African Management Development Institute (SAMDI), OctoberThe overall aim of this research project was to evaluate the process of implementing the CDW programme through a learnership. The specific objectives of the project, therefore, were to evaluate the recruitment and selection procedures of the CDWs in order to ensure the best matching of people with the job description, review and evaluate the overall training intervention in order to determine its effectiveness in providing CDWs with the appropriate skills to perform their duties, define and augment the job description of the CDWs during the research and evaluation process in order to identify focused key performance areas
and ensure effective service delivery, and evaluate the effectiveness of the service delivery by the CDWs in the communities where possible
The influence of antiretroviral treatment on willingness to test: a qualitative study in rural KwaZulu-Natal, South Africa
Applying the Precaution Adoption Process Model to the Acceptance of Mine Safety and Health Technologies
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The atacama cosmology telescope: A measurement of the cosmic microwave background power spectra at 98 and 150 GHz
We present the temperature and polarization angular power spectra of the CMB measured by the Atacama Cosmology Telescope (ACT) from 5400 deg2 of the 2013â2016 survey, which covers >15000 deg2 at 98 and 150 GHz. For this analysis we adopt a blinding strategy to help avoid confirmation bias and, related to this, show numerous checks for systematic error done before unblinding. Using the likelihood for the cosmological analysis we constrain secondary sources of anisotropy and foreground emission, and derive a âCMB-onlyâ spectrum that extends to ` = 4000. At large angular scales, foreground emission at 150 GHz is âŒ1% of TT and EE within our selected regions and consistent with that found by Planck. Using the same likelihood, we obtain the cosmological parameters for ÎCDM for the ACT data alone with a prior on the optical depth of Ï = 0.065 ± 0.015. ÎCDM is a good fit. The best-fit model has a reduced Ï2 of 1.07 (PTE = 0.07) with H0 = 67.9 ± 1.5 km/s/Mpc. We show that the lensing BB signal is consistent with ÎCDM and limit the celestial EB polarization angle to ÏP = â0.07⊠±0.09âŠ. We directly cross correlate ACT with Planck and observe generally good agreement but with some discrepancies in TE. All data on which this analysis is based will be publicly released