98 research outputs found
BICEP: a large angular scale CMB polarimeter
We describe the design and expected performance of BICEP, a millimeter wave receiver designed to measure the polarization of the cosmic microwave background. BICEP uses an array of polarization sensitive bolometers operating at 100 and 150 GHz to measure polarized signals over a 20 degree field of view with 1 degree resolution. BICEP is designed with particular attention to systematic effects which can potentially degrade the polarimetric fidelity of the observations. BICEP is optimized to detect the faint signature of a primordial gravitational wave background which is a generic prediction of inflationary cosmologies
Radio Sources in Galaxy Clusters at 28.5 GHz
We present serendipitous detections of radio sources at 28.5 GHz (1 cm),
which resulted from our program to image thermal Sunyaev-Zeldovich (SZ) effect
in 56 galaxy clusters. We find 64 radio sources with fluxes down to 0.4 mJy,
and within 250 arcseconds from the pointing centers. The spectral indices (S ~
\nu^-\alpha) of 54 sources with published low frequency flux densities range
from -0.6 to 2 with a mean of 0.77, and a median of 0.84. Extending low
frequency surveys of radio sources towards galaxy clusters CL 0016+16, Abell
665, and Abell 2218 to 28.5 GHz, and selecting sources with 1.4 GHz flux
density greater than 7 mJy to form an unbiased sample, we find a mean spectral
index of 0.71 and a median of 0.71. We find 4 to 7 times more sources predicted
from a low frequency survey in areas without galaxy clusters. This excess
cannot be accounted for by gravitational lensing of a background radio
population by cluster potentials, indicating most of the detected sources are
associated with galaxy clusters. For the cluster Abell 2218, the presence of
unsubtracted radio sources with 28.5 GHz flux densities less than 0.5 mJy, can
only contribute to temperature fluctuations at a level of 10 to 25 \muK. The
corresponding error due to radio point source contamination in the Hubble
constant derived through a combined analysis of 28.5 GHz SZ images and X-ray
emission observations ranges from 1% to 6%.Comment: 18 pages, 8 figures, to appear in April 1998 issue of A
CMB polarimetry with BICEP: instrument characterization, calibration, and performance
BICEP is a ground-based millimeter-wave bolometric array designed to target
the primordial gravity wave signature on the polarization of the cosmic
microwave background (CMB) at degree angular scales. Currently in its third
year of operation at the South Pole, BICEP is measuring the CMB polarization
with unprecedented sensitivity at 100 and 150 GHz in the cleanest available 2%
of the sky, as well as deriving independent constraints on the diffuse
polarized foregrounds with select observations on and off the Galactic plane.
Instrument calibrations are discussed in the context of rigorous control of
systematic errors, and the performance during the first two years of the
experiment is reviewed.Comment: 12 pages, 15 figures, updated version of a paper accepted for
Millimeter and Submillimeter Detectors and Instrumentation for Astronomy IV,
Proceedings of SPIE, 7020, 200
Absolute polarization angle calibration using polarized diffuse Galactic emission observed by BICEP
We present a method of cross-calibrating the polarization angle of a
polarimeter using BICEP Galactic observations. \bicep\ was a ground based
experiment using an array of 49 pairs of polarization sensitive bolometers
observing from the geographic South Pole at 100 and 150 GHz. The BICEP
polarimeter is calibrated to +/-0.01 in cross-polarization and less than +/-0.7
degrees in absolute polarization orientation. BICEP observed the temperature
and polarization of the Galactic plane (R.A= 100 degrees ~ 270 degrees and Dec.
= -67 degrees ~ -48 degrees). We show that the statistical error in the 100 GHz
BICEP Galaxy map can constrain the polarization angle offset of WMAP Wband to
0.6 degrees +\- 1.4 degrees. The expected 1 sigma errors on the polarization
angle cross-calibration for Planck or EPIC are 1.3 degrees and 0.3 degrees at
100 and 150 GHz, respectively. We also discuss the expected improvement of the
BICEP Galactic field observations with forthcoming BICEP2 and Keck
observations.Comment: 13 pages, 10 figures and 2 tables. To appear in Proceedings of SPIE
Astronomical Telescopes and Instrumentation 201
Determining the Cosmic Distance Scale from Interferometric Measurements of the Sunyaev-Zel'dovich Effect
We determine the distances to 18 galaxy clusters with redshifts ranging from
z~0.14 to z~0.78 from a maximum likelihood joint analysis of 30 GHz
interferometric Sunyaev-Zel'dovich effect (SZE) and X-ray observations. We
model the intracluster medium (ICM) using a spherical isothermal beta model. We
quantify the statistical and systematic uncertainties inherent to these direct
distance measurements, and we determine constraints on the Hubble parameter for
three different cosmologies. These distances imply a Hubble constant of 60 (+4,
-4) (+13, -18) km s-1 Mpc-1 for an Omega_M = 0.3, Omega_Lambda = 0.7 cosmology,
where the uncertainties correspond to statistical followed by systematic at 68%
confidence. With a sample of 18 clusters, systematic uncertainties clearly
dominate. The systematics are observationally approachable and will be
addressed in the coming years through the current generation of X-ray
satellites (Chandra & XMM-Newton) and radio observatories (OVRO, BIMA, & VLA).
Analysis of high redshift clusters detected in future SZE and X-ray surveys
will allow a determination of the geometry of the universe from SZE determined
distances.Comment: ApJ Submitted; 40 pages, 9 figures (fig 3 B&W for size constraint),
13 tables, uses emulateapj5 styl
BICEP: a large angular scale CMB polarimeter
We describe the design and expected performance of BICEP, a millimeter wave receiver designed to measure the polarization of the cosmic microwave background. BICEP uses an array of polarization sensitive bolometers operating at 100 and 150 GHz to measure polarized signals over a 20 degree field of view with 1 degree resolution. BICEP is designed with particular attention to systematic effects which can potentially degrade the polarimetric fidelity of the observations. BICEP is optimized to detect the faint signature of a primordial gravitational wave background which is a generic prediction of inflationary cosmologies
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