THE ATACAMA COSMOLOGY TELESCOPE: CALIBRATION WITH THE WILKINSON MICROWAVE ANISOTROPY PROBE USING CROSS-CORRELATIONS
ASTROPHYSICAL JOURNAL 740:2 (2011) ARTN 86
The atacama cosmology telescope (ACT): Beam profiles and first SZ cluster maps
Astrophysical Journal, Supplement Series 191:2 (2010) 423-438
Abstract:
TheAtacamaCosmology Telescope (ACT) is currently observing the cosmicmicrowave background with arcminute resolution at 148 GHz, 218 GHz, and 277 GHz. In this paper, we present ACT's first results. Data have been analyzed using a maximum-likelihood map-making method which uses B-splines to model and remove the atmospheric signal. It has been used to make high-precision beam maps from which we determine the experiment's window functions. This beam information directly impacts all subsequent analyses of the data. We also used the method to map a sample of galaxy clusters via the Sunyaev-Zel'dovich (SZ) effect and show five clusters previously detected with X-ray or SZ observations. We provide integrated Compton-y measurements for each cluster. Of particular interest is our detection of the z = 0.44 component of A3128 and our current non-detection of the low-redshift part, providing strong evidence that the further cluster is more massive as suggested by X-ray measurements. This is a compelling example of the redshift-independent mass selection of the SZ effect. © 2010. The American Astronomical Society.The Atacama Cosmology Telescope: Physical properties and purity of a galaxy cluster sample selected via the Sunyaev-Zel'dovich effect
Astrophysical Journal 723:2 (2010) 1523-1541
Abstract:
We present optical and X-ray properties for the first confirmed galaxy cluster sample selected by the Sunyaev-Zel'dovich effect (SZE) from 148 GHz maps over 455 deg2 of sky made with the Atacama Cosmology Telescope (ACT). These maps, coupled with multi-band imaging on 4 m class optical telescopes, have yielded a sample of 23 galaxy clusters with redshifts between 0.118 and 1.066. Of these 23 clusters, 10 are newly discovered. The selection of this sample is approximately mass limited and essentially independent of redshift. We provide optical positions, images, redshifts, and X-ray fluxes and luminosities for the full sample, and X-ray temperatures of an important subset. The mass limit of the full sample is around 8.0 × 1014 M ⊙, with a number distribution that peaks around a redshift of 0.4. For the 10 highest significance SZE-selected cluster candidates, all of which are optically confirmed, the mass threshold is 1 × 1015 M⊙ and the redshift range is 0.167-1.066. Archival observations from Chandra, XMM-Newton, and ROSAT provide X-ray luminosities and temperatures that are broadly consistent with this mass threshold. Our optical follow-up procedure also allowed us to assess the purity of the ACT cluster sample. Eighty (one hundred) percent of the 148 GHz candidates with signal-to-noise ratios greater than 5.1 (5.7) are confirmed as massive clusters. The reported sample represents one of the largest SZE-selected sample of massive clusters over all redshifts within a cosmologically significant survey volume, which will enable cosmological studies as well as future studies on the evolution, morphology, and stellar populations in the most massive clusters in the universe. © 2010. The American Astronomical Society.The Atacama Cosmology Telescope: A measurement of the 600 < ℓ < 8000 cosmic microwave background power spectrum at 148 GHz
Astrophysical Journal 722:2 (2010) 1148-1161
Abstract:
We present a measurement of the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz. The measurement uses maps with 1′.4 angular resolution made with data from the Atacama Cosmology Telescope (ACT). The observations cover 228 deg2 of the southern sky, in a 4°.2 wide strip centered on declination 53° south. The CMB at arcminute angular scales is particularly sensitive to the Silk damping scale, to the Sunyaev-Zel'dovich (SZ) effect from galaxy clusters, and to emission by radio sources and dusty galaxies. After masking the 108 brightest point sources in our maps, we estimate the power spectrum between 600 < ℓ < 8000 using the adaptive multi-taper method to minimize spectral leakage and maximize use of the full data set. Our absolute calibration is based on observations of Uranus. To verify the calibration and test the fidelity of our map at large angular scales, we cross-correlate the ACT map to the WMAP map and recover the WMAP power spectrum from 250 < ℓ < 1150. The power beyond the Silk damping tail of the CMB (ℓ ∼ 5000) is consistent with models of the emission from point sources. We quantify the contribution of SZ clusters to the power spectrum by fitting to a model normalized to σ 8 = 0.8. We constrain the model's amplitude ASZ < 1.63 (95% CL). If interpreted as a measurement of σ 8, this implies σ 8SZ < 0.86 (95% CL) given our SZ model. A fit of ACT and WMAP five-year data jointly to a six-parameter ACDM model plus point sources and the SZ effect is consistent with these results. © 2010. The American Astronomical Society. All rights reserved. Printed in the U.S.A.The Atacama Cosmology Telescope: Calibration with WMAP Using Cross-Correlations
ArXiv 1009.0777 (2010)