[show abstract][hide abstract] ABSTRACT: We present the XMM-Newton follow-up for validation of Planck cluster candidates. Twenty-five candidates have been observed to date using snapshot (~10 ksec) exposures: ten as part of a pilot programme to sample a low range of signal-to-noise ratios (45 candidates. The sensitivity and spatial resolution of XMM-Newton allows unambiguous discrimination between clusters and false candidates. A total of 21 candidates are confirmed as extended X-ray sources. Seventeen are single clusters, the majority of which are found to have highly irregular and disturbed morphologies. The remaining four sources are multiple systems, including the unexpected discovery of a supercluster at z=0.45. For most of the sources we are able to derive a redshift estimate from the X-ray Fe K line (albeit of variable quality). The new clusters span the redshift range 0.09 <~ z <~ 0.54 with a median redshift of z ~ 0.37. A first estimate is made of their X-ray properties including the characteristic size, which is used to improve the SZ Compton parameter estimate. The validation programme has helped to optimise the Planck candidate selection process. It has also provided a preview of the X-ray properties of these newly-discovered clusters, allowing comparison to their SZ properties, and to the X-ray and SZ properties of known clusters observed in the Planck survey. Our results suggest that Planck may have started to reveal a non-negligible population of massive dynamically perturbed objects that is under-represented in X-ray surveys. However, despite their particular properties, these new clusters appear to follow the Ysz-Yx relation established for X-ray selected objects.
[show abstract][hide abstract] ABSTRACT: We present the first all-sky sample of galaxy clusters detected blindly by the Planck satellite through the Sunyaev-Zeldovich (SZ) effect from its six highest frequencies. This Early SZ (ESZ) sample of 189 candidates comprises high signal-to-noise clusters, from 6 to 29. Its high reliability (purity above 95%) is further insured by an extensive validation process based on Planck-internal quality assessments and external cross-identification and follow-up observations. Planck provides the first measured SZ signal for about 80% of the 169 ESZ known clusters. Planck further releases 30 new cluster candidates among which 20 are within the ESZ signal-to-noise selection criterion. Eleven of these 20 ESZ candidates are confirmed using XMM-Newton snapshot observations as new clusters, most of them with disturbed morphologies and low luminosities. The ESZ clusters are mostly at moderate redshifts (86% with z below 0.3) and span over a decade in mass, up to the rarest and most massive clusters with masses above 10^15 Msol.
[show abstract][hide abstract] ABSTRACT: The performance of the Planck instruments in space is enabled by their low operating temperatures, 20K for LFI and 0.1K for HFI, achieved through a combination of passive radiative cooling and three active mechanical coolers. Active coolers were chosen to minimize straylight on the detectors and to maximize lifetime. The scientific requirement for very broad frequency led to two detector technologies with widely different temperature and cooling needs. This made use of a helium cryostat, as used by previous cryogenic space missions (IRAS, COBE, ISO, SPITZER, AKARI), infeasible. Radiative cooling is provided by three V-groove radiators and a large telescope baffle. The active coolers are a hydrogen sorption cooler (<20K), a 4He Joule-Thomson cooler (4.7K), and a 3He-4He dilution cooler (1.4K and 0.1K). The flight system was at ambient temperature at launch and cooled in space to operating conditions. The bolometer plate of the High Frequency Instrument reached 93mK on 3 July 2009, 50 days after launch. The solar panel always faces the Sun, shadowing the rest of Planck, and operates at a mean temperature of 384K. At the other end of the spacecraft, the telescope baffle operates at 42.3K and the telescope primary mirror operates at 35.9K. The temperatures of key parts of the instruments are stabilized by both active and passive methods. Temperature fluctuations are driven by changes in the distance from the Sun, sorption cooler cycling and fluctuations in gas-liquid flow, and fluctuations in cosmic ray flux on the dilution and bolometer plates. These fluctuations do not compromise the science data.
[show abstract][hide abstract] ABSTRACT: Planck's all sky surveys at 30-857 GHz provide an unprecedented opportunity to follow the radio spectra of a large sample of extragalactic sources to frequencies 2-20 times higher than allowed by past, large area, ground-based surveys. We combine the results of the Planck Early Release Compact Source Catalog (ERCSC) with quasi-simultaneous ground-based observations, as well as archival data, at frequencies below or overlapping Planck frequency bands, to validate the astrometry and photometry of the ERCSC radio sources and study the spectral features shown in this new frequency window opened by Planck. The ERCSC source positions and flux density scales are found to be consistent with the ground-based observations. We present and discuss the spectral energy distributions (SEDs) of a sample of "extreme" radio sources to illustrate the richness of the ERCSC for the study of extragalactic radio sources. Variability is found to play a role in the unusual spectral features of some of these sources.
[show abstract][hide abstract] ABSTRACT: We present new measurements of CIB anisotropies using Planck. Combining HFI
data with IRAS, the angular auto- and cross frequency power spectrum is
measured from 143 to 3000 GHz, and the auto-bispectrum from 217 to 545 GHz. The
total areas used to compute the CIB power spectrum and bispectrum are about
2240 and 4400 deg^2, respectively. After careful removal of the contaminants,
and a complete study of systematics, the CIB power spectrum and bispectrum are
measured with unprecedented signal to noise ratio from angular multipoles
ell~150 to 2500, and ell~130 to 1100, respectively. Two approaches are
developed for modelling CIB power spectrum anisotropies. The first approach
takes advantage of the unique measurements by Planck at large angular scales,
and models only the linear part of the power spectrum, with a mean bias of dark
matter halos hosting dusty galaxies at a given redshift weighted by their
contribution to the emissivities. The second approach is based on a model that
associates star-forming galaxies with dark matter halos and their subhalos,
using a parametrized relation between the dust-processed infrared luminosity
and (sub-)halo mass. The two approaches simultaneously fit all auto- and cross-
power spectra very well. We find that the star formation history is well
constrained up to z~2. However, at higher redshift, the accuracy of the star
formation history measurement is strongly degraded by the uncertainty in the
spectral energy distribution of CIB galaxies. We also find that CIB galaxies
have warmer temperatures as redshift increases. The CIB bispectrum is steeper
than that expected from the power spectrum, although well fitted by a power
law; this gives some information about the contribution of massive halos to the
[show abstract][hide abstract] ABSTRACT: The Q/U Imaging ExperimenT (QUIET) is designed to measure polarization in the cosmic microwave background, targeting the imprint of inflationary gravitational waves at large angular scales(~1°). Between 2008 October and 2010 December, two independent receiver arrays were deployed sequentially on a 1.4 m side-fed Dragonian telescope. The polarimeters that form the focal planes use a compact design based on high electron mobility transistors (HEMTs) that provides simultaneous measurements of the Stokes parameters Q, U, and I in a single module. The 17-element Q-band polarimeter array, with a central frequency of 43.1 GHz, has the best sensitivity (69 μKs1/2) and the lowest instrumental systematic errors ever achieved in this band, contributing to the tensor-to-scalar ratio at r < 0.1. The 84-element W-band polarimeter array has a sensitivity of 87 μKs1/2 at a central frequency of 94.5 GHz. It has the lowest systematic errors to date, contributing at r < 0.01. The two arrays together cover multipoles in the range ℓ ~ 25-975. These are the largest HEMT-based arrays deployed to date. This article describes the design, calibration, performance, and sources of systematic error of the instrument.
The Astrophysical Journal 05/2013; 768(1):9. · 6.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: We present the current estimate of instrumental and systematic effect uncertainties of the Planck-Low Frequency Instrument relative to the first release of the Planck cosmological results. We discuss an overview of the main effects and of the tools and methods applied to assess the residuals on maps and power spectra. We also present an overall budget of systematic effect uncertainties, which are dominated by far sidelobe straylight pick-up and imperfect calibration. They are at least two orders of magnitude less than the CMB temperature power spectrum. A residual spurious signal above the noise level is present, especially at 30 GHz, in the multipole range l < 20 and is likely to be caused by residual galactic straylight contamination. Current analysis aims to further reduce the level of spurious signals in the data and to better model systematic effects, in particular straylight and calibration uncertainties.