629 research outputs found
A 3D model for carbon monoxide molecular line emission as a potential cosmic microwave background polarization contaminant
We present a model for simulating Carbon Monoxide (CO) rotational line emission in molecular clouds, taking account of their 3D spatial distribution in galaxies with different geometrical properties. The model implemented is based on recent results in the literature and has been designed for performing Monte-Carlo simulations of this emission. We compare the simulations produced with this model and calibrate them, both on the map level and on the power spectrum level, using the second release of data from the Planck satellite for the Galactic plane, where the signal-to-noise ratio is highest. We use the calibrated model to extrapolate the CO power spectrum at low Galactic latitudes where no high sensitivity observations are available yet. We then forecast the level of unresolved polarized emission from CO molecular clouds which could contaminate the power spectrum of Cosmic Microwave Background (CMB) polarization B-modes away from the Galactic plane. Assuming realistic levels of the polarization fraction, we show that the level of contamination is equivalent to a cosmological signal with r 720.02. The Monte-Carlo MOlecular Line Emission (MCMole3D) Python package, which implements this model, is being made publicly available
Bayesian evidence of the post-Planck curvaton
We perform a Bayesian model comparison for scenarios within the quadratic curvaton model, determining the degree to which both are disfavoured with respect to the ÎCDM concordance model and single-field quadratic inflation, using the recent Planck data release. Despite having three additional model parameters, the simplest curvaton scenario is not disfavoured relative to single-field quadratic inflation, and it becomes favoured against this single-field model when we include the joint BICEP/Keck/Planck analysis. In all cases we assume an instantaneous inflaton decay and no surviving isocurvature perturbations. Despite the success of Planck reaching its forecast measurement accuracy, we show that the current constraints on local non-Gaussianity are insufficiently precise to have any significant impact on the evidence ratios so far. We also determine the precision Ï(fNL) required by future measurements assuming a fiducial value of fNL = â5/4 or 10.8 to no longer disfavour the curvaton against the ÎCDM parametrisation, and we discuss the effect that the predicted increase in precision from future measurements on fNL may have. We show that our results are not very sensitive to our choice of priors
Expected constraints on the Galactic magnetic field using PLANCK data
We explore in this paper the ability to constrain the Galactic magnetic field
intensity and spatial distribution with the incoming data from the Planck
satellite experiment. We perform realistic simulations of the Planck
observations at the polarized frequency bands from 30 to 353 GHz for two
all-sky surveys as expected for the nominal mission. These simulations include
CMB, synchrotron and thermal dust Galactic emissions and instrumental noise.
(Note that systematic effects are not considered in this paper). For the
synchrotron and thermal dust Galactic emissions we use a coherent 3D model of
the Galaxy describing its mater density and the magnetic field direction and
intensity. We first simulate the synchrotron and dust emissions at 408 MHz and
545 GHz, respectively, and then we extrapolate them to the Planck frequency
bands. We perform a likelihood analysis to compare the simulated data to a set
of models obtained by varying the pitch angle of the regular magnetic field
spatial distribution, the relative amplitude of the turbulent magnetic field,
the radial scale of the electron and dust grain distributions, and the
extrapolation spectral indices for the synchrotron and thermal dust emissions.
We are able to set tight constraints on all the parameters considered. We have
also found that the observed spatial variations of the synchrotron and thermal
dust spectral indices should not affect our ability to recover the other
parameters of the model. From this, we conclude that the Planck satellite
experiment can precisely measure the main properties of the Galactic magnetic
field. An accurate reconstruction of the matter distribution would require on
the one hand an improved modelling of the ISM and on the other hand to use
extra data sets like rotation measurements of pulsars.Comment: A&A accepte
Non-Gaussianity from false vacuum inflation: Old curvaton scenario
We calculate the three-point correlation function of the comoving curvature
perturbation generated during an inflationary epoch driven by false vacuum
energy. We get a novel false vacuum shape bispectrum, which peaks in the
equilateral limit. Using this result, we propose a scenario which we call "old
curvaton". The shape of the resulting bispectrum lies between the local and the
false vacuum shapes. In addition we have a large running of the spectral index.Comment: 13 pages, 3 figures; v2 with minor revison; v3 final version to
appear on JCA
Nonlinear superhorizon perturbations of non-canonical scalar field
We develop a theory of non-linear cosmological perturbations at superhorizon
scales for a scalar field with a Lagrangian of the form , where
and is the scalar field. We
employ the ADM formalism and the spatial gradient expansion approach to obtain
general solutions valid up to the second order in the gradient expansion. This
formulation can be applied to, for example, DBI inflation models to investigate
superhorizon evolution of non-Gaussianities. With slight modification, we also
obtain general solutions valid up to the same order for a perfect fluid with a
general equation of state .Comment: 14 page
Planck 2013 results. IX. HFI spectral response
The Planck High Frequency Instrument (HFI) spectral response was determined
through a series of ground based tests conducted with the HFI focal plane in a
cryogenic environment prior to launch. The main goal of the spectral
transmission tests was to measure the relative spectral response (including
out-of-band signal rejection) of all HFI detectors. This was determined by
measuring the output of a continuously scanned Fourier transform spectrometer
coupled with all HFI detectors. As there is no on-board spectrometer within
HFI, the ground-based spectral response experiments provide the definitive data
set for the relative spectral calibration of the HFI. The spectral response of
the HFI is used in Planck data analysis and component separation, this includes
extraction of CO emission observed within Planck bands, dust emission,
Sunyaev-Zeldovich sources, and intensity to polarization leakage. The HFI
spectral response data have also been used to provide unit conversion and
colour correction analysis tools. Verifications of the HFI spectral response
data are provided through comparisons with photometric HFI flight data. This
validation includes use of HFI zodiacal emission observations to demonstrate
out-of-band spectral signal rejection better than 10^8. The accuracy of the HFI
relative spectral response data is verified through comparison with
complementary flight-data based unit conversion coefficients and colour
correction coefficients. These coefficients include those based upon HFI
observations of CO, dust, and Sunyaev-Zeldovich emission. General agreement is
observed between the ground-based spectral characterization of HFI and
corresponding in-flight observations, within the quoted uncertainty of each;
explanations are provided for any discrepancies.Comment: 27 pages, 28 figures, one of the papers associated with the 2013
Planck data releas
Planck 2015 results. V. LFI calibration
We present a description of the pipeline used to calibrate the Planck Low Frequency Instrument (LFI) timelines into thermodynamic temperatures for the Planck 2015 data release, covering four years of uninterrupted operations. As in the 2013 data release, our calibrator is provided by the spin-synchronous modulation of the cosmic microwave background dipole, but we now use the orbital component, rather than adopting the Wilkinson Microwave Anisotropy Probe (WMAP) solar dipole. This allows our 2015 LFI analysis to provide an independent Solar dipole estimate, which is in excellent agreement with that of HFI and within 1Ï (0.3% in amplitude) of the WMAP value. This 0.3% shift in the peak-to-peak dipole temperature from WMAP and a general overhaul of the iterative calibration code increases the overall level of the LFI maps by 0.45% (30âGHz), 0.64% (44âGHz), and 0.82% (70âGHz) in temperature with respect to the 2013 Planck data release, thus reducing the discrepancy with the power spectrum measured by WMAP. We estimate that the LFI calibration uncertainty is now at the level of 0.20% for the 70âGHz map, 0.26% for the 44âGHz map, and 0.35% for the 30âGHz map. We provide a detailed description of the impact of all the changes implemented in the calibration since the previous data release
Planck 2015 results. VI. LFI mapmaking
This paper describes the mapmaking procedure applied to Planck Low Frequency Instrument (LFI) data. The mapmaking step takes as input the calibrated timelines and pointing information. The main products are sky maps of I, Q, and U Stokes components. For the first time, we present polarization maps at LFI frequencies. The mapmaking algorithm is based on a destriping technique, which is enhanced with a noise prior. The Galactic region is masked to reduce errors arising from bandpass mismatch and high signal gradients. We apply horn-uniform radiometer weights to reduce the effects of beam-shape mismatch. The algorithm is the same as used for the 2013 release, apart from small changes in parameter settings. We validate the procedure through simulations. Special emphasis is put on the control of systematics, which is particularly important for accurate polarization analysis. We also produce low-resolution versions of the maps and corresponding noise covariance matrices. These serve as input in later analysis steps and parameter estimation. The noise covariance matrices are validated through noise Monte Carlo simulations. The residual noise in the map products is characterized through analysis of half-ring maps, noise covariance matrices, and simulations
Planck 2013 results. XXXI. Consistency of the Planck data
The Planck design and scanning strategy provide many levels of redundancy that can be exploited to provide tests of internal consistency. One of the most important is the comparison of the 70 GHz (amplifier) and 100 GHz (bolometer) channels. Based on different instrument technologies, with feeds located differently in the focal plane, analysed independently by different teams using different software, and near the minimum of diffuse foreground emission, these channels are in effect two different experiments. The 143 GHz channel has the lowest noise level on Planck, and is near the minimum of unresolved foreground emission. In this paper, we analyse the level of consistency achieved in the 2013 Planck data. We concentrate on comparisons between the 70, 100, and 143 GHz channel maps and power spectra, particularly over the angular scales of the first and second acoustic peaks, on maps masked for diffuse Galactic emission and for strong unresolved sources. Difference maps covering angular scales from 8 to 15' are consistent with noise, and show no evidence of cosmic microwave background structure. Including small but important corrections for unresolved-source residuals, we demonstrate agreement (measured by deviation of the ratio from unity) between 70 and 100 GHz power spectra averaged over 70 64 l 64390 at the 0.8% level, and agreement between 143 and 100 GHz power spectra of 0.4% over the same l range. These values are within and consistent with the overall uncertainties in calibration given in the Planck 2013 results. We also present results based on the 2013 likelihood analysis showing consistency at the 0.35% between the 100, 143, and 217 GHz power spectra. We analyse calibration procedures and beams to determine what fraction of these differences can be accounted for by known approximations or systematicerrors that could be controlled even better in the future, reducing uncertainties still further. Several possible small improvements are described. Subsequent analysis of the beams quantifies the importance of asymmetry in the near sidelobes, which was not fully accounted for initially, affecting the 70/100 ratio. Correcting for this, the 70, 100, and 143 GHz power spectra agree to 0.4% over the first two acoustic peaks. The likelihood analysis that produced the 2013 cosmological parameters incorporated uncertainties larger than this. We show explicitly that correction of the missing near sidelobe power in the HFI channels would result in shifts in the posterior distributions of parameters of less than 0.3\u3c3 except for As, the amplitude of the primordial curvature perturbations at 0.05 Mpc-1, which changes by about 1\u3c3. We extend these comparisons to include the sky maps from the complete nine-year mission of the Wilkinson Microwave Anisotropy Probe (WMAP), and find a roughly 2% difference between the Planck and WMAP power spectra in the region of the first acoustic peak. \ua9 ESO, 2014
Planck 2013 results X. Energetic particle effects: characterization, removal, and simulation
This paper presents the detection, interpretation and removal of the signal
resulting from interactions of high energy particles with the Planck High
Frequency Instrument (HFI). These interactions fall into two categories,
heating the 0.1 K bolometer plate and glitches in each detector time stream.
Glitch shapes are not simple single pole exponential decays and fall into a
three families. The glitch shape for each family has been characterized
empirically in flight data and removed from the detector time streams. The
spectrum of the count rate/unit energy is computed for each family and a
correspondence to where on the detector the particle hit is made. Most of the
detected glitches are from galactic protons incident on the Si die frame
supporting the micromachined bolometric detectors. At HFI, the particle flux is
~ 5 per square cm and per second and is dominated by protons incident on the
spacecraft with an energy >39 MeV, leading to a rate of typically one event per
second and per detector. Different categories of glitches have different
signature in timestreams. Two of the glitch types have a low amplitude
component that decays over nearly 1 second. This component produces an 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 removal method removes excess
noise from glitches. Using realistic simulations, we find this method does not
introduce signal bias.Comment: 23 pages; v2: author list complete
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