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Register a new userA Map of the Cosmic Microwave Background from the BEAST Experiment
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We present the first sky maps from the BEAST (Background Emission Anisotropy Scanning Telescope) experiment. BEAST consists of a 2.2 meter off axis Gregorian telescope fed by a cryogenic millimeter wavelength focal plane currently consisting of 6 Q band (40 GHz) and 2 Ka band (30 GHz) scalar feed horns feeding cryogenic HEMT amplifiers. Data were collected from two balloon-borne flights in 2000, followed by a lengthy ground observing campaign from the 3.8 Km altitude University of California White Mountain Research Station. This paper reports the initial results from the ground based observations. The instrument produced an annular map covering the sky from declinateion 33 to 42 degrees. The maps cover an area of 2470 square degrees with an effective resolution of 23 arcminutes FWHM at 40 GHz and 30 arcminutes at 30 GHz. The map RMS (smoothed to 30 arcminutes and excluding galactic foregrounds) is 54 +-5 microK at 40 GHz. Comparison with the instrument noise gives a cosmic signal RMS contribution of 28 +-3 microK. An estimate of the actual CMB sky signal requires taking into account the l-space filter function of our experiment and analysis techniques, carried out in a companion paper (ODwyer et al. 2003). In addition to the robust detection of CMB anisotropies, we find a strong correlation between small portions of our maps and features in recent H$alpha$ maps (Finkbeiner, 2003). In this work we describe the data set and analysis techniques leading to the maps, including data selection, filtering, pointing reconstruction, mapmaking algorithms and systematic effects. A detailed description of the experiment appears in Childers et al. (2003).
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We present Cosmic Microwave Background (CMB) maps from the Santa Barbara HACME balloon experiment (Staren etal 2000), covering about 1150 square degrees split between two regions in the northern sky, near the stars gamma Ursae Minoris and alpha Leonis, respectively. The FWHM of the beam is about 0.77 degrees in 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 offsets. The maps display no striping, and the noise correlations are found to be virtually isotropic, decaying on an angular scale around one degree. 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 bodes 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 offsets will be as dominant as for HACME, the problems they pose can be readily overcome with the mapmaking algorithm discussed. Our prewhitened notch-filter algorithm for destriping and offset removal should be useful also for other balloon- and ground-based experiments whose scan strategies involve substantial interleaving.
Simulated observations of a $10dg times 10dg$ field by the Microwave Anisotropy Probe (MAP) are analysed in order to separate cosmic microwave background (CMB) emission from foreground contaminants and instrumental noise and thereby determine how accurately the CMB emission can be recovered. The simulations include emission from the CMB, the kinetic and thermal Sunyaev-Zeldovich (SZ) effects from galaxy clusters, as well as Galactic dust, free-free and synchrotron. We find that, even in the presence of these contaminating foregrounds, the CMB map is reconstructed with an rms accuracy of about 20 $mu$K per 12.6 arcmin pixel, which represents a substantial improvement as compared to the individual temperature sensitivities of the raw data channels. We also find, for the single $10dg times 10dg$ field, that the CMB power spectrum is accurately recovered for $ell la 600$.
The Background Emission Anisotropy Scanning Telescope (BEAST) is a 2.2m off-axis telescope with an 8 element mixed Q (38-45GHz) and Ka (26-36GHz) band focal plane, designed for balloon borne and ground based studies of the Cosmic Microwave Background. Here we present the Cosmic Microwave Background (CMB) angular power spectrum calculated from 682 hours of data observed with the BEAST instrument. We use a binned pseudo-Cl estimator (the MASTER method). We find results that are consistent with other determinations of the CMB anisotropy for angular wavenumber l between 100 and 600. We also perform cosmological parameter estimation. The BEAST data alone produces a good constraint on Omega_k = 1-Omega_tot=-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.
We describe the Millimeter wave Anisotropy eXperiment IMaging Array (MAXIMA), a balloon-borne experiment designed to measure the temperature anisotropy of the Cosmic Microwave Background (CMB) on angular scales of 10 to 5 degrees . MAXIMA mapped the CMB using 16 bolometric detectors in spectral bands centered at 150 GHz, 240 GHz, and 410 GHz, with 10 resolution at all frequencies. The combined receiver sensitivity to CMB anisotropy was ~40 microK/rt(sec). Systematic parasitic contributions were minimized by using four uncorrelated spatial modulations, thorough crosslinking, multiple independent CMB observations, heavily baffled optics, and strong spectral discrimination. Pointing reconstruction was accurate to 1, and absolute calibration was better than 4%. Two MAXIMA flights with more than 8.5 hours of CMB observations have mapped a total of 300 deg^2 of the sky in regions of negligible known foreground emission. MAXIMA results have been released in previous publications. MAXIMA maps, power spectra and correlation matrices are publicly available at http://cosmology.berkeley.edu/maxima
MADmap is a software application used to produce maximum-likelihood images of the sky from time-ordered data which include correlated noise, such as those gathered by Cosmic Microwave Background (CMB) experiments. It works efficiently on platforms ranging from small workstations to the most massively parallel supercomputers. Map-making is a critical step in the analysis of all CMB data sets, and the maximum-likelihood approach is the most accurate and widely applicable algorithm; however, it is a computationally challenging task. This challenge will only increase with the next generation of ground-based, balloon-borne and satellite CMB polarization experiments. The faintness of the B-mode signal that these experiments seek to measure requires them to gather enormous data sets. MADmap is already being run on up to $O(10^{11})$ time samples, $O(10^8)$ pixels and $O(10^4)$ cores, with ongoing work to scale to the next generation of data sets and supercomputers. We describe MADmaps algorithm based around a preconditioned conjugate gradient solver, fast Fourier transforms and sparse matrix operations. We highlight MADmaps ability to address problems typically encountered in the analysis of realistic CMB data sets and describe its application to simulations of the Planck and EBEX experiments. The massively parallel and distributed implementation is detailed and scaling complexities are given for the resources required. MADmap is capable of analysing the largest data sets now being collected on computing resources currently available, and we argue that, given Moores Law, MADmap will be capable of reducing the most massive projected data sets.
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