8 research outputs found
Planck 2013 results. X. HFI energetic particle effects: characterization, removal, and simulation
Get PDFWe describe the detection, interpretation, and removal of the signal resulting from interactions of high energy particles with the Planck High Frequency Instrument (HFI). There are two types of interactions: heating of the 0.1 K bolometer plate; and glitches in each detector time stream. The transientresponses to detector glitch shapes are not simple single-pole exponential decays and fall into three families. The glitch shape for each family has been characterized empirically in flight data and these shapes have been used to remove glitches from the detector time streams. The spectrum of the count rate per unit energy is computed for each family and a correspondence is made to the location on the detector of the particle hit. Most of the detected glitches are from Galactic protons incident on the die frame supporting the micro-machined bolometric detectors. In the Planck orbit at L2, the particle flux is around 5 cm-2 s-1 and is dominated by protons incident on the spacecraft with energy >39 MeV, at a rate of typically one event per second per detector. Different categories of glitches have different signatures in the time stream. Two of the glitch types have a low amplitude component that decays over nearly 1 s. This component produces excess noise if not properly removed from the time-ordered data. We have used a glitch detection and subtraction method based on the joint fit of population templates. The application of this novel glitch subtraction method removes excess noise from the time streams. Using realistic simulations, we find that this method does not introduce signal bias into the Planck data.
Reproduced with permission from Astronomy & Astrophysics, © ESO 201
Planck 2013 results. XIX. The integrated Sachs-Wolfe effect
Get PDFBased on cosmic microwave background (CMB) maps from the 2013 Planck
Mission data release, this paper presents the detection of the
integrated Sachs-Wolfe (ISW) effect, that is, the correlation between
the CMB and large-scale evolving gravitational potentials. The
significance of detection ranges from 2 to 4sigma, depending on which
method is used. We investigated three separate approaches, which
essentially cover all previous studies, and also break new ground. (i)
We correlated the CMB with the Planck reconstructed gravitational
lensing potential (for the first time). This detection was made using
the lensing-induced bispectrum between the low-l and high-l
temperature anisotropies; the correlation between lensing and the ISW
effect has a significance close to 2.5sigma. (ii) We cross-correlated
with tracers of large-scale structure, which yielded a significance of
about 3sigma, based on a combination of radio (NVSS) and optical
(SDSS) data. (iii) We used aperture photometry on stacked CMB fields at
the locations of known large-scale structures, which yielded and
confirms a 4sigma signal, over a broader spectral range, when using a
previously explored catalogue, but shows strong discrepancies in
amplitude and scale when compared with expectations. More recent
catalogues give more moderate results that range from negligible to
2.5sigma at most, but have a more consistent scale and amplitude, the
latter being still slightly higher than what is expected from numerical
simulations within LambdaCMD. Where they can be compared, these
measurements are compatible with previous work using data from WMAP,
where these scales have been mapped to the limits of cosmic variance.
Planck's broader frequency coverage allows for better foreground
cleaning and confirms that the signal is achromatic, which makes it
preferable for ISW detection. As a final step we used tracers of
large-scale structure to filter the CMB data, from which we present maps
of the ISW temperature perturbation. These results provide complementary
and independent evidence for the existence of a dark energy component
that governs the currently accelerated expansion of the Universe
Planck 2013 results.:XV. CMB power spectra and likelihood
Get PDFThis paper presents the Planck 2013 likelihood, a complete statistical description of the two-point correlation function of the CMB temperature fluctuations that accounts for all known relevant uncertainties, both instrumental and astrophysical in nature. We use this likelihood to derive our best estimate of the CMB angular power spectrum from Planck over three decades in multipole moment, covering 22500. The main source of uncertainty at 1500 is cosmic variance. Uncertainties in small-scale foreground modelling and instrumental noise dominate the error budget at higher s. For <50, our likelihood exploits all Planck frequency channels from 30 to 353 GHz, separating the cosmological CMB signal from diffuse Galactic foregrounds through a physically motivated Bayesian component separation technique. At 50, we employ a correlated Gaussian likelihood approximation based on a fine-grained set of angular cross-spectra derived from multiple detector combinations between the 100, 143, and 217 GHz frequency channels, marginalising over power spectrum foreground templates. We validate our likelihood through an extensive suite of consistency tests, and assess the impact of residual foreground and instrumental uncertainties on the final cosmological parameters. We find good internal agreement among the high-cross-spectra with residuals below a few K2 at 1000, in agreement with estimated calibration uncertainties. We compare our results with foreground-cleaned CMB maps derived from all Planck frequencies, as well as with cross-spectra derived from the 70 GHz Planck map, and find broad agreement in terms of spectrum residuals and cosmological parameters. We further show that the best-fit CDM cosmology is in excellent agreement with preliminary PlanckEE and TE polarisation spectra. We find that the standard CDM cosmology is well constrained by Planck from the measurements at 1500. One specific example is the spectral index of scalar perturbations, for which we report a 5.4 deviation from scale invariance, n= 1. Increasingthe multipole range beyond 1500 does not increase our accuracy for the CDM parameters, but instead allows us to study extensions beyond the standard model. We find no indication of significant departures from the CDM framework. Finally, we report a tension between the Planck best-fit CDM model and the low-spectrum in the form of a power deficit of 510% at 40, with a statistical significance of 2.53. Without a theoretically motivated model for this power deficit, we do not elaborate further on its cosmological implications, but note that this is our most puzzling finding in an otherwise remarkably consistent data set
