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Register a new userObserving the CMB at High-l using the VSA and AMI
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Angela C. Taylor
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We discuss two experiments - the Very Small Array (VSA) and the Arcminute MicroKelvin Imager (AMI) - and their prospects for observing the CMB at high angular multipoles. Whilst the VSA is primarily designed to observe primary anisotropies in the CMB, AMI is designed to image secondary anisotropies via the Sunyaev-Zeldovich effect. The combined l-range of these two instruments is between l = 150 and ~10000.
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We have observed the cosmic microwave background (CMB) in three regions of sky using the Very Small Array (VSA) in an extended configuration with antennas of beamwidth 2 degrees at 34 GHz. Combined with data from previous VSA observations using a more compact array with larger beamwidth, we measure the power spectrum of the primordial CMB anisotropies between angular multipoles l = 160 - 1400. Such measurements at high l are vital for breaking degeneracies in parameter estimation from the CMB power spectrum and other cosmological data. The power spectrum clearly resolves the first three acoustic peaks, shows the expected fall off in power at high l and starts to constrain the position and height of a fourth peak.
Accurate calibration of data is essential for the current generation of CMB experiments. Using data from the Very Small Array (VSA), we describe procedures which will lead to an accuracy of 1 percent or better for experiments such as the VSA and CBI. Particular attention is paid to the stability of the receiver systems, the quality of the site and frequent observations of reference sources. At 30 GHz the careful correction for atmospheric emission and absorption is shown to be essential for achieving 1 percent precision. The sources for which a 1 percent relative flux density calibration was achieved included Cas A, Cyg A, Tau A and NGC7027 and the planets Venus, Jupiter and Saturn. A flux density, or brightness temperature in the case of the planets, was derived at 33 GHz relative to Jupiter which was adopted as the fundamental calibrator. A spectral index at ~30 GHz is given for each. Cas A,Tau A, NGC7027 and Venus were examined for variability. Cas A was found to be decreasing at $0.394 pm 0.019$ percent per year over the period March 2001 to August 2004. In the same period Tau A was decreasing at $0.22pm 0.07$ percent per year. A survey of the published data showed that the planetary nebula NGC7027 decreased at $0.16pm 0.04$ percent per year over the period 1967 to 2003. Venus showed an insignificant ($1.5 pm 1.3$ percent) variation with Venusian illumination. The integrated polarization of Tau A at 33 GHz was found to be $7.8pm 0.6$ percent at pa $ = 148^circ pm 3^circ$.}
The AMI Galactic Plane Survey (AMIGPS) is a large area survey of the outer Galactic plane to provide arcminute resolution images at milli-Jansky sensitivity in the centimetre-wave band. Here we present the first data release of the survey, consisting of 868 deg^2 of the Galactic plane, covering the area 76 deg lessapprox l lessapprox 170 deg between latitudes of |b| lessapprox 5 deg, at a central frequency of 15.75 GHz (1.9 cm). We describe in detail the drift scan observations which have been used to construct the maps, including the techniques used for observing, mapping and source extraction, and summarise the properties of the finalized datasets. These observations constitute the most sensitive Galactic plane survey of large extent at centimetre-wave frequencies greater than 1.4 GHz.
BICEP3 is a 520 mm aperture on-axis refracting telescope at the South Pole, which observes the polarization of the cosmic microwave background (CMB) at 95 GHz to search for the B-mode signal from inflationary gravitational waves. In addition to this main target, we have developed a low-elevation observation strategy to extend coverage of the Southern sky at the South Pole, where BICEP3 can quickly achieve degree-scale E-mode measurements over a large area. An interesting E-mode measurement is probing a potential polarization anomaly around the CMB Cold Spot. During the austral summer seasons of 2018-19 and 2019-20, BICEP3 observed the sky with a flat mirror to redirect the beams to various low elevation ranges. The preliminary data analysis shows degree-scale E-modes measured with high signal-to-noise ratio.
Accurate short-term load forecasting is essential for efficient operation of the power sector. Predicting load at a fine granularity such as individual households or buildings is challenging due to higher volatility and uncertainty in the load. In aggregate loads such as at grids level, the inherent stochasticity and fluctuations are averaged-out, the problem becomes substantially easier. We propose an approach for short-term load forecasting at individual consumers (households) level, called Forecasting using Matrix Factorization (FMF). FMF does not use any consumers demographic or activity patterns information. Therefore, it can be applied to any locality with the readily available smart meters and weather data. We perform extensive experiments on three benchmark datasets and demonstrate that FMF significantly outperforms the computationally expensive state-of-the-art methods for this problem. We achieve up to 26.5% and 24.4 % improvement in RMSE over Regression Tree and Support Vector Machine, respectively and up to 36% and 73.2% improvement in MAPE over Random Forest and Long Short-Term Memory neural network, respectively.
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