Estimate of the Cosmological Bispectrum from the MAXIMA-1 Cosmic Microwave Background Map

We use the measurement of the cosmic microwave background taken during the MAXIMA-1 flight to estimate the bispectrum of cosmological perturbations. We propose an estimator for the bispectrum that is appropriate in the flat sky approximation, apply it to the MAXIMA-1 data and evaluate errors using bootstrap methods. We compare the estimated value with what would be expected if the sky signal were Gaussian and find that it is indeed consistent, with a $\chi^2$ per degree of freedom of approximately unity. This measurement places constraints on models of inflation.Comment: 5 pages, 2 figures. New version to match paper accepted for publication in Phys. Rev. Lett. Non-diagonal terms included leading to new limits on f_N

Observations of internal bores and waves of elevation on the New England inner continental shelf during summer 2001

Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 110 (2005): C03020, doi:10.1029/2004JC002377.During July–August 2001, oceanographic variability on the New England inner continental shelf was investigated with an emphasis on temporal scales shorter than tidal periods. Mooring and ship survey data showed that subtidal variation of inner shelf stratification was in response to regional Ekman upwelling and downwelling wind driven dynamics. High-frequency variability in the vertical structure of the water column at an offshore mooring site was linked to the baroclinic internal tide and the onshore propagation of nonlinear solitary waves of depression. Temperature, salinity, and velocity data measured at an inshore mooring detected a bottom bore that formed on the flood phase of the tide. During the ebb tide, a second bottom discontinuity and series of nonlinear internal waves of elevation (IWOE) formed when the water column became for a time under hydraulic control. A surface manifestation of these internal wave crests was also observed in aircraft remote sensing imagery. The coupling of IWOE formation to the offshore solitary waves packets was investigated through internal wave breaking criterion derived in earlier laboratory studies. Results suggested that the offshore solitons shoaled on the sloping shelf, and transformed from waves of depression to waves of elevation. The coupling of inshore bore formation to the offshore solitary waves and the possible impact of these periodic features on mixing on the inner shelf region are discussed.This work was funded by the Office of Naval Research under grant N00014-99-1-0029 and Secretary of the Navy/CNO Chair grant N00014-99-1-0090 to R. A. W

Operation of a 1-Liter-Volume Gaseous Argon Scintillation Counter

We have built a gas-phase argon ionization detector to measure small nuclear recoil energies (< 10 keVee). In this paper, we describe the detector response to X-ray and gamma calibration sources, including analysis of pulse shapes, software triggers, optimization of gas content, and energy- and position-dependence of the signal. We compare our experimental results against simulation using a 5.9-keV X-ray source, as well as higher-energy gamma sources up to 1332 keV. We conclude with a description of the detector, DAQ, and software settings optimized for a measurement of the low-energy nuclear quenching factor in gaseous argon. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory in part under Contract W-7405-Eng-48 and in part under Contract DE-AC52-07NA27344. Funded by Lab-wide LDRD. LLNL-JRNL-415990-DRAFT.Comment: 29 pages, single-column, double-spaced, 21 figure

Determining Foreground Contamination in CMB Observations: Diffuse Galactic Emission in the MAXIMA-I Field

Observations of the CMB can be contaminated by diffuse foreground emission from sources such as Galactic dust and synchrotron radiation. In these cases, the morphology of the contaminating source is known from observations at different frequencies, but not its amplitude at the frequency of interest for the CMB. We develop a technique for accounting for the effects of such emission in this case, and for simultaneously estimating the foreground amplitude in the CMB observations. We apply the technique to CMB data from the MAXIMA-1 experiment, using maps of Galactic dust emission from combinations of IRAS and DIRBE observations, as well as compilations of Galactic synchrotron emission observations. The spectrum of the dust emission over the 150--450 GHz observed by MAXIMA is consistent with preferred models but the effect on CMB power spectrum observations is negligible.Comment: 19 pages, 8 figures, accepted for publication in the Astrophysical Journal. Monor changes to match the published versio

MAXIMA: an experiment to measure temperature anisotropy in the cosmic microwave background

We describe the MAXIMA experiment, a balloon-borne measurement designed to map temperature anisotropy in the Cosmic Microwave Background (CMB) over a wide range of angular scales (multipole range 80 < l < 800). The experiment consists of a 1.3 m diameter off-axis Gregorian telescope and a receiver with a 16 element array of bolometers cooled to 100 mK. The frequency bands are centered at 150, 240, and 410 GHz. The 10' FWHM beam sizes are well matched to the scale of acoustic peaks expected in the angular power spectrum of the CMB. The first flight of the experiment in its full configuration was launched in August 1998. A 122 sq-deg map of the sky was made near the Draco constellation during the 7 hour flight in a region of extremely low galactic dust contamination. This map covers 0.3% of the sky and has 3200 independent beamsize pixels. We describe the MAXIMA instrument and its performance during the recent flight.Comment: To appear in proceedings of `3K Cosmology', ed. F Melchiorri, Conference held Oct 5-10 1998, Rome, 13 pages LaTeX (using aipproc2.sty & aipproc2.cls), Postscript with higher resolution graphics available at http://cfpa.berkeley.edu/group/cmb/gen.htm

MAXIPOL: Cosmic Microwave Background Polarimetry Using a Rotating Half-Wave Plate

We discuss MAXIPOL, a bolometric balloon-borne experiment designed to measure the E-mode polarization of the cosmic microwave background radiation (CMB). MAXIPOL is the first bolometric CMB experiment to observe the sky using rapid polarization modulation. To build MAXIPOL, the CMB temperature anisotropy experiment MAXIMA was retrofitted with a rotating half-wave plate and a stationary analyzer. We describe the instrument, the observations, the calibration and the reduction of data collected with twelve polarimeters operating at 140 GHz and with a FWHM beam size of 10 arcmin. We present maps of the Q and U Stokes parameters of an 8 deg^2 region of the sky near the star Beta Ursae Minoris. The power spectra computed from these maps give weak evidence for an EE signal. The maximum-likelihood amplitude of l(l+1)C^{EE}_{l}/(2 pi) is 55_{-45}^{+51} uK^2 (68%), and the likelihood function is asymmetric and skewed positive such that with a uniform prior the probability that the amplitude is positive is 96%. This result is consistent with the expected concordance LCDM amplitude of 14 uK^2. The maximum likelihood amplitudes for l(l+1)C^{BB}_{l}/(2 pi) and $\ell(\ell+1)C^{EB}_{\ell}/2\pi$ are -31_{-19}^{+31} and 18_{-34}^{+27} uK^2 (68%), respectively, which are consistent with zero. All of the results are for one bin in the range 151 < l < 693. Tests revealed no residual systematic errors in the time or map domain. A comprehensive discussion of the analysis of the data is presented in a companion paper.Comment: 19 pages, 11 figures, 2 tables, submitted to Ap

3D Position Sensitive XeTPC for Dark Matter Search

The technique to realize 3D position sensitivity in a two-phase xenon time projection chamber (XeTPC) for dark matter search is described. Results from a prototype detector (XENON3) are presented.Comment: Presented at the 7th UCLA Symposium on "Sources and Detection of Dark Matter and Dark Energy in the Universe

Observations and modeling of coastal internal waves driven by a diurnal sea breeze

During the Internal Waves on the Continental Margin (IWAVES) field experiments of 1996 and 1997 off of Mission Beach, California (32.75° N), we observed energetic, dirunal-band motions across the entire study site in water depths ranging from 15 to 500 m and spanning a cross-shore distance of 15 km. The spectral peak of the currents was at the diurnal frequency (σD₁ = 1 cpd) and was sufficiently well resolved to be clearly separated from the slightly higher local inertial frequency (f = 1.08 cpd). These motions were surface enhanced and clockwise circularly polarized and had an upward phase propagation speed of ~68 m d¯¹, suggesting that the motions were driven predominantly by the diurnal sea breeze. However, the downward energy (upward phase) propagation seems irreconcilable with the subinertial diurnal period, and moreover, the intermittent diurnal current events were not obviously associated with the diurnal sea breeze events. We rationalize these features using a flat-bottomed linear modal sum internal wave model that includes advection and refraction due to subtidal alongshore flow, V(x,t). Fluctuations in V at the observing site can change the “effective” local Coriolis parameter f + Vx by as much 50%, thus making the diurnal motions at different times effectively either subinertial or superinertial. The model is integrated numerically for 200 days at a latitude of 32.75°N under different wind and subtidal flow conditions: purely diurnal winds and no V, purely diurnal winds and a time-independent V, narrow-band diurnal winds and no V, and narrow-band diurnal winds and subtidal, time-dependent V. Model diurnal currents forced by narrow-band diurnal winds and subtidal V show complex offshore structure with realistic intermittency and spectral broadening. This study suggests that continental margins in the vicinity of the 30° latitude (where σD₁ = f) are regions that could potentially produce energetic, sea breeze-driven baroclinic motions and that these motions could be regulated by the vorticity of the local subtidal currents

Observations of the semidiurnal internal tide on the southern California slope and shelf

We give a detailed description of the semidiurnal-band current and temperature variability observed during the Internal Waves on the Continental Margin (IWAVES) field experiments of 1996 and 1997 off of Mission Beach, California. This variability was dominated by the internal tide, and the structure of the internal tide on the slope and shelfbreak region was different from that on the narrow shelf. On the slope and shelfbreak, the internal tide was dominated by alongshore propagating coastal-trapped waves. In this region, semidiurnal-band currents were predominantly oriented in the alongshore direction. In the lower half of the water column at a water depth H of 350 m, current and temperature variability were consonant with a short wavelength (~8 km) bottom trapped wave propagating in the alongshore direction to the north. In the upper 120 m of the water column (above the depth of the shelfbreak), slope and shelfbreak currents were highly coherent with a zero phase lag; that is, there was no phase propagation in the cross-shore direction. On the narrow (~10 km) shelf, cross-shore currents u were much more energetic than on the slope and had the structure of a mode-one internal wave. The alongshore currents v decreased monotonically from the surface to the bottom of the water column with a phase that did not change with depth. The near-bottom u signal propagated toward the coast during all mooring deployments, faster in the summer than in the fall. The near-bottom u and mid-column temperature relative phase was neither consistent with a purely progressive nor a purely standing mode-one internal wave. We conclude that the internal tide on the shelf was partially reflected.Copyrighted by American Geophysical Union.Keywords: continental shelf and slope circulation, internal tide, coastal-trapped wave, internal wave