The cosmic microwave background radiation (CMBR) has a blackbody spectrum within 3.4 x 10(exp -8) ergs/sq cm/s/sr cm over the frequency range from 2 to 20/cm (5-0.5 mm). These measurements, derived ...from the Far-Infrared Absolute Spectrophotomer (FIRAS) instrument on the Cosmic Background Explorer (COBE) satellite, imply stringent limits on energy release in the early universe after t approximately 1 year and redshift z approximately 3 x 10(exp 6). The deviations are less than 0.30% of the peak brightness, with an rms value of 0.01%, and the dimensionless cosmological distortion parameters are limited to the absolute value of y is less than 2.5 x 10(exp -5) and the absolute value of mu is less than 3.3 x 10(exp -4) (95% confidence level). The temperature of the CMBR is 2.726 +/- 0.010 K (95% confidence level systematic).
We describe data reduction and analysis of fluctuations in the cosmic far-IR background (CFIB) in observations with the Multiband Imaging Photometer for Spitzer (MIPS) instrument 160 μm detectors. We ...analyzed observations of an 8.5 square degree region in the Lockman Hole, part of the largest low-cirrus mapping observation with this instrument. We measured the power spectrum of the CFIB in these observations by fitting a power law to the IR cirrus component, the dominant foreground contaminant, and subtracting this cirrus signal. The CFIB power spectrum in the range 0.2 arcmin-1 < k < 0.5 arcmin-1 is consistent with previous measurements of a relatively flat component. However, we find a large power excess at low k, which falls steeply to the flat component in the range 0.03 arcmin-1 < k < 0.1 arcmin-1. This low-k power spectrum excess is consistent with predictions of a source clustering “signature”. This is the first report of such a detection in the far-IR.
The scientific performance of the Planck Low Frequency Instrument (LFI) after one year of in-orbit operation is presented. We describe the main optical parameters and discuss photometric calibration, ...white noise sensitivity, and noise properties. A preliminary evaluation of the impact of the main systematic effects is presented. For each of the performance parameters, we outline the methods used to obtain them from the flight data and provide a comparison with pre-launch ground assessments, which are essentially confirmed in flight.
Preliminary models of microwave emission from the Milky Way Galaxy based on COBE and other data are constructed for the purpose of distinguishing cosmic and Galactic signals. Differential Microwave ...Radiometer (DMR) maps, with the modeled Galactic emission removed, are fitted for a quadrupole distribution. Autocorrelation functions for individual Galactic components are presented. When Galactic emission is removed from the DMR data, the residual fluctuations are virtually unaffected, and therefore they are not dominated by any known Galactic emission component.
MAXIPOL: Data Analysis and Results Wu, J. H. P; Zuntz, J; Abroe, M. E ...
Astrophysical journal/The Astrophysical journal,
08/2007, Letnik:
665, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We present results from and the analysis of data from MAXIPOL, a balloon-borne experiment designed to measure the polarization in the cosmic microwave background (CMB). MAXIPOL is the first CMB ...experiment to obtain results using a rotating half-wave plate as a rapid polarization modulator. We report results from observations of a sky area of 8 deg super(2) with 10' resolution, providing information up to l similar to 700. We use a maximum likelihood method to estimate maps of the Q and U Stokes parameters from the demodulated time streams, and then both Bayesian and frequentist approaches to compute the EE, EB, and BB power spectra. Detailed formalisms of the analyses are given. We give results for the amplitude of the power spectra assuming different shape functions within the l bins, with and without a prior C super(E) sub(l) super(B) = C super(B) sub(l) super(B) = 0, and with and without inclusion of calibration uncertainty. We show results from systematic tests including differencing of maps, analyzing sky areas of different sizes, assessing the influence of leakage from temperature to polarization, and quantifying the Gaussianity of the maps. We find no evidence for systematic errors. The Bayesian analysis gives weak evidence for an EE signal. The EE power is 55 super(+) sub(-) super(5) sub(4) super(1) sub(5) mu K super(2) at the 68% confidence level for l = 151-693. Its likelihood function is asymmetric and skewed positive such that with a uniform prior the probability of a positive EE power is 96%. The powers of EB and BB signals at the 68% confidence level are 18 super(+) sub(-) super(2) sub(3) super(7) sub(4) and -31 super(+) sub(-) super(8) sub(1) super(1) sub(9) mu K super(2), respectively, and thus consistent with zero. The upper limit of the BB-mode at the 95% confidence level is 9.5 mu K. Results from the frequentist approach are in agreement within statistical errors. These results are consistent with the current concordance ACDM model.
We describe the processing of data from the Low Frequency Instrument (LFI) used in production of the Planck Early Release Compact Source Catalogue (ERCSC). In particular, we discuss the steps ...involved in reducing the data from telemetry packets to cleaned, calibrated, time-ordered data (TOD) and frequency maps. Data are continuously calibrated using the modulation of the temperature of the cosmic microwave background radiation induced by the motion of the spacecraft. Noise properties are estimated from TOD from which the sky signal has been removed using a generalized least square map-making algorithm. Measured 1/f noise knee-frequencies range from ~100 mHz at 30 GHz to a few tens of mHz at 70GHz. A destriping code (Madam) is employed to combine radiometric data and pointing information into sky maps, minimizing the variance of correlated noise. Noise covariance matrices required to compute statistical uncertainties on LFI and Planck products are also produced. Main beams are estimated down to the ≈−10dB level using Jupiter transits, which are also used for geometrical calibration of the focal plane.
The context of this study is the development of polarisation sensitive detectors in view of future Cosmic Microwave Background experiments. Our goal is to demonstrate the possibility to make a ...mm-wave polarisation analyser at 150 GHz using Lumped Element Kinetic Inductance Detectors (LEKIDs). Although LEKIDs are very attractive for the relative ease of fabrication, they have an intrinsic optical response which is weakly polarisation-senstive, i.e. orthogonal linear polarisations are absorbed with comparable efficiencies (with a separation typically not exceeding few dB). To overcome this difficulty, we achieve a polarised response by means of small (
∼
λ
×
λ
) superconducting Nb wire-grids. Each grid is deposited on the rear side of the 300 micron Si substrate, on which 20 nm Al resonators are patterned, so that each pixel may in principle respond as an independent polarisation analyser. Simulations show encouraging results, with a deep (-20 dB) rejection of the unwanted polarisation. Although what we present here is not yet a polarimeter, this pilot study allows us to address some relevant questions that may be crucial in view of a full polarimetric architecture development. In particular, our first prototypes will allow to assess the behaviour of small grids, the interaction between adjacent polarised pixels, and to choose the most suitable resonator geometry. What we present here are preliminary design results about devices which are currently being realised, and soon ready for optical response characterisation.
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