Jeffrey Childers

The Cosmic Microwave Background Anisotropy Power Spectrum from the BEAST Experiment

The Background Emission Anisotropy Scanning Telescope (BEAST) is a 2.2 m off-axis telescope with an eightelement mixed Q-band (38–45 GHz) and Ka-band (26–36 GHz) focal plane, designed for balloon-borne and ground-basedstudiesofthe cosmicmicrowavebackground(CMB).Herewepresentthe CMB angularpowerspectrumcalculatedfrom682hrofdataobservedwiththeBEASTinstrument.Weuseabinnedpseudo-Cl estimator(the MASTER method). We find results that are consistent with other determinations of the CMB anisotropy for angular wavenumbers l between 100 and 600. We also perform cosmological parameter estimation. The BEAST data alone produce a good constraint on k � 1 � tot ¼� 0:074 � 0:070, consistent with a flat universe. A joint parameter estimation analysis with a number of previous CMB experiments produces results consistent with previous determinations. Subject heading gs: cosmicmicrowavebackground — cosmology:observations — large-scalestructureofuniverse

A Spin-Modulated Telescope to Make Two-Dimensional Cosmic Microwave Background Maps

We describe the HEMT Advanced Cosmic Microwave Explorer (HACME), a balloon-borne experiment designed to measure subdegree-scale cosmic microwave background anisotropy over hundreds of deg2, using a unique two-dimensional scanning strategy. A spinning flat mirror that is canted relative to its spin axis modulates the direction of beam response in a nearly elliptical path on the sky. The experiment was successfully flown in 1996 February, achieving near laboratory performance for several hours at float altitude. A map free of instrumental systematic effects is produced for a 3.5 hr observation of 630 deg2, resulting in a flat-band power upper limit of l(l + 1)Cl/(2π)0.5 < 77 μK at l = 38 (95% confidence). The experiment design, flight operations, and data, including atmospheric effects and noise performance, are discussed.

COSMIC MICROWAVE BACKGROUND MAPS FROM THE HACME EXPERIMENT

We present cosmic microwave background (CMB) maps from the Santa Barbara HACME balloon experiment (Staren et al.), covering about 1150 square degrees split between two regions in the northern sky, near the stars c Ursae Minoris and a Leonis, respectively. The FWHM of the beam is in D0i.77 three frequency bands centered on 39, 41, and 43 GHz. The results demonstrate that the thoroughly interconnected scan strategy employed allows efficient removal of 1/f-noise and slightly variable scan- synchronous oUsets. The maps display no striping, and the noise correlations are found to be virtually isotropic, decaying on an angular scale D1i. The noise performance of the experiment resulted in an upper limit on CMB anisotropy. However, our results demonstrate that atmospheric contamination and other systematics resulting from the circular scanning strategy can be accurately controlled and bode well for the planned follow-up experiments BEAST and ACE, since they show that even with the overly cautious assumption that 1/f-noise and oUsets will be as dominant as for HACME, the problems they pose can be readily overcome with the mapmaking algorithm discussed. Our prewhitened notch-—lter algorithm for destriping and oUset removal is proving useful also for other balloon- and ground-based experiments whose scan strategies involve substantial interleaving, e.g., Boomerang. Subject headings: balloonscosmic microwave backgroundcosmology: observations On-line material: color —gures

Angular power spectrum of the FastICA CMB component from BEAST data

We present the angular power spectrum of the CMB component extracted with FastICA from the Background Emission Anisotropy Scanning Telescope (BEAST) data. BEAST is a 2.2 meter off-axis telescope with a focal plane comprising 8 elements at Q (38-45 GHz) and Ka (26-36 GHz) bands. It operates from the UC White Montain Research Station at an altitude of 3800 meters. The BEAST CMB angular power spectrum has been already calculated by O’Dwyer et al. using only the Q band data. With two input channels FastICA returns two possible independent component. We found that one of these two is unphysical while the other is a reasonable CMB component. After a detailed calibration procedure based on Monte-Carlo (MC) simulations we extracted the angular power spectrum for the identified CMB component and found a very good agreement with the already published BEAST CMB angular power spectrum and with the W MAP data.

Imaging the cosmic microwave background: The BEAST experiment

We describe the Santa Barbara BEAST experiment, a balloon borne telescope to image the Cosmic Microwave Background (CMB) radiation anisotropy pattern. Some aspects of the map making pipeline are also discussed.