M. Newcomb

HIGH-RESOLUTION OBSERVATIONS OF THE COSMIC MICROWAVE BACKGROUND POWER SPECTRUM WITH ACBAR

We report the first measurements of anisotropy in the cosmic microwave background (CMB) radiation with the Arcminute Cosmology Bolometer Array Receiver (ACBAR). The instrument was installed on the 2.1 m Viper telescope at the South Pole in 2001 January; the data presented here are the product of observations up to and including 2002 July. We present two deep differential maps produced by subtracting leading and trailing observations from the main field. The differential maps cover approximately 24 deg2 of sky selected for low dust contrast. These results represent the highest signal-to-noise ratio observations of CMB anisotropy to date; in the deepest 150 GHz band map, we reached an rms of ~8.0 μK per 5 beam. The 3° extent of the maps and small beam size of the experiment allow the measurement of the CMB anisotropy power spectrum over the range l = 150-3000 with resolution of Δl = 150. The contributions of galactic dust and radio sources to the observed anisotropy are negligible and are removed in the analysis. The resulting power spectrum is found to be consistent with the primary anisotropy expected in a concordance ΛCDM universe.

Estimates of cosmological parameters using the cosmic microwave background angular power spectrum of ACBAR

We report an investigation of cosmological parameters based on the measurements of anisotropy in the cosmic microwave background radiation (CMB) made by the Arcminute Cosmology Bolometer Array Receiver (ACBAR). We use the ACBAR data in concert with other recent CMB measurements to derive Bayesian estimates of parameters in inflation-motivated adiabatic cold dark matter models. We apply a series of additional cosmological constraints on the shape and amplitude of the density power spectrum and the Hubble parameter and from supernovae to further refine our parameter estimates. Previous estimates of parameters are confirmed, with sensitive measurements of the power spectrum now ranging from l ~ 3 to 2800. Comparing individual best-fit models, we find that the addition of ΩΛ as a parameter dramatically improves the fits. We also use the high-l data of ACBAR, along with similar data from the Cosmic Background Imager and Berkeley-Illinois-Maryland Association array, to investigate potential secondary anisotropies from the Sunyaev-Zeldovich effect. We show that the results from the three experiments are consistent under this interpretation and use the data, combined and individually, to estimate σ8 from the Sunyaev-Zeldovich component.

ACBAR: the Arcminute Cosmology Bolometer Array Receiver

We describe the Arcminute Cosmology Bolometer Array Receiver (ACBAR); a multifrequency millimeter-wave receiver designed for observations of the cosmic microwave background and the Sunyaev-Zeldovich effect in clusters of galaxies. The ACBAR focal plane consists of a 16 pixel, background-limited, 240 mK bolometer array that can be configured to observe simultaneously at 150, 220, 280, and 350 GHz. With 4-5 FWHM beams and a 3° azimuth chop, ACBAR is sensitive to a wide range of angular scales. ACBAR was installed on the 2 m Viper telescope at the South Pole in 2001 January. We describe the design of the instrument and its performance during the 2001 and 2002 observing seasons.

Sunyaev-Zeldovich Observations of Massive Clusters of Galaxies

We present detections of the Sunyaev‐Zeldovich Effect (SZE) at 150GHz and 275GHz for the X‐ray luminous z=0.299 cluster 1E0657‐67. These observations were obtained as part of an X‐ray, weak lensing, and SZE survey of nearby X‐ray bright clusters. The SZE maps were made with the ACBAR (150, 210, 275 GHz) bolometer array installed at the Viper telescope located at the South Pole. We also present preliminary results from a blind SZE cluster survey.

First results from the arcminute cosmology bolometer array receiver

Abstract We review the first science results from the Arcminute Cosmology Bolometer Array Receiver (ACBAR); a multi-frequency millimeter-wave receiver optimized for observations of the Cosmic Microwave Background (CMB) and the Sunyaev–Zel’dovich (SZ) effect in clusters of galaxies. ACBAR was installed on the 2 m Viper telescope at the South Pole in January 2001 and the results presented here incorporate data through July 2002. We present the power spectrum of the CMB at 150 GHz over the range l=150–3000 measured by ACBAR as well as estimates for the values of the cosmological parameters within the context of ΛCDM models. We find that the inclusion of Ω Λ greatly improves the fit to the power spectrum. We also observe a slight excess of small-scale anisotropy at 150 GHz; if interpreted as power from the SZ effect of unresolved clusters, the measured signal is consistent with CBI and BIMA within the context of the SZ power spectrum models tested.