27 research outputs found
Planck early results. XIII. Statistical properties of extragalactic radio sources in the Planck Early Release Compact Source Catalogue
The data reported in Planckâs Early Release Compact Source Catalogue (ERCSC) are exploited to measure the number counts (dN/dS) of
extragalactic radio sources at 30, 44, 70, 100, 143 and 217 GHz. Due to the full-sky nature of the catalogue, this measurement extends to the
rarest and brightest sources in the sky. At lower frequencies (30, 44, and 70 GHz) our counts are in very good agreement with estimates based on
WMAP data, being somewhat deeper at 30 and 70 GHz, and somewhat shallower at 44 GHz. Planckâs source counts at 143 and 217 GHz join
smoothly with the fainter ones provided by the SPT and ACT surveys over small fractions of the sky. An analysis of source spectra, exploiting
Planckâs uniquely broad spectral coverage, finds clear evidence of a steepening of the mean spectral index above about 70 GHz. This implies
that, at these frequencies, the contamination of the CMB power spectrum by radio sources below the detection limit is significantly lower than
previously estimated
Planck Early Results XVIII: The power spectrum of cosmic infrared background anisotropies
Using Planck maps of six regions of low Galactic dust emission with a total area of about 140 deg2, we determine the angular power spectra of
cosmic infrared background (CIB) anisotropies from multipole â = 200 to â = 2000 at 217, 353, 545 and 857 GHz. We use 21-cm observations of
Hi as a tracer of thermal dust emission to reduce the already low level of Galactic dust emission and use the 143 GHz Planck maps in these fields
to clean out cosmic microwave background anisotropies. Both of these cleaning processes are necessary to avoid significant contamination of the
CIB signal. We measure correlated CIB structure across frequencies. As expected, the correlation decreases with increasing frequency separation,
because the contribution of high-redshift galaxies to CIB anisotropies increases with wavelengths. We find no significant difference between the
frequency spectrum of the CIB anisotropies and the CIB mean, with âI/I=15% from 217 to 857 GHz. In terms of clustering properties, the
Planck data alone rule out the linear scale- and redshift-independent bias model. Non-linear corrections are significant. Consequently, we develop
an alternative model that couples a dusty galaxy, parametric evolution model with a simple halo-model approach. It provides an excellent fit to
the measured anisotropy angular power spectra and suggests that a different halo occupation distribution is required at each frequency, which
is consistent with our expectation that each frequency is dominated by contributions from different redshifts. In our best-fit model, half of the
anisotropy power at â=2000 comes from redshifts z 2 at 353
and 217 GHz, respectively
Planck early results XVIII : The power spectrum of cosmic infrared background anisotropies
Peer reviewe
Planck early results. XX. New light on anomalous microwave emission from spinning dust grains
Anomalous microwave emission (AME) has been observed by numerous experiments in the frequency range âŒ10â60 GHz. Using Planck maps
and multi-frequency ancillary data, we have constructed spectra for two known AME regions: the Perseus and Ï Ophiuchi molecular clouds. The
spectra are well fitted by a combination of free-free radiation, cosmic microwave background, thermal dust, and electric dipole radiation from
small spinning dust grains. The spinning dust spectra are the most precisely measured to date, and show the high frequency side clearly for the
first time. The spectra have a peak in the range 20â40 GHz and are detected at high significances of 17.1Ï for Perseus and 8.4Ï for Ï Ophiuchi.
In Perseus, spinning dust in the dense molecular gas can account for most of the AME; the low density atomic gas appears to play a minor role.
In Ï Ophiuchi, the âŒ30 GHz peak is dominated by dense molecular gas, but there is an indication of an extended tail at frequencies 50â100 GHz,
which can be accounted for by irradiated low density atomic gas. The dust parameters are consistent with those derived from other measurements.
We have also searched the Planck map at 28.5 GHz for candidate AME regions, by subtracting a simple model of the synchrotron, free-free, and
thermal dust. We present spectra for two of the candidates; S140 and S235 are bright Hii regions that show evidence for AME, and are well fitted
by spinning dust models
Planck early results. II. The thermal performance of Planck
The performance of the Planck instruments in space is enabled by their low operating temperatures, 20 K for LFI and 0.1 K for HFI, achieved
through a combination of passive radiative cooling and three active mechanical coolers. The scientific requirement for very broad frequency
coverage led to two detector technologies with widely different temperature and cooling needs. Active coolers could satisfy these needs; a helium
cryostat, as used by previous cryogenic space missions (IRAS, COBE, ISO, Spitzer, AKARI), could not. Radiative cooling is provided by three
V-groove radiators and a large telescope baffle. The active coolers are a hydrogen sorption cooler (<20 K), a 4He Joule-Thomson cooler (4.7 K),
and a 3He-4He dilution cooler (1.4 K and 0.1 K). The flight system was at ambient temperature at launch and cooled in space to operating
conditions. The HFI bolometer plate reached 93 mK 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 384 K. At the other end of the spacecraft, the telescope baffle operates at 42.3 K and the
telescope primary mirror operates at 35.9 K. 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
Planck Early Results. VII. The Early Release Compact Source Catalogue
A brief description of the methodology of construction, contents and usage of the Planck Early Release Compact Source Catalogue (ERCSC),
including the Early Cold Cores (ECC) and the Early Sunyaev-Zeldovich (ESZ) cluster catalogue is provided. The catalogue is based on data that
consist of mapping the entire sky once and 60% of the sky a second time by Planck, thereby comprising the first high sensitivity radio/submillimetre
observations of the entire sky. Four source detection algorithms were run as part of the ERCSC pipeline. A Monte-Carlo algorithm based on the
injection and extraction of artificial sources into the Planck maps was implemented to select reliable sources among all extracted candidates such
that the cumulative reliability of the catalogue is â„90%. There is no requirement on completeness for the ERCSC. As a result of the Monte-Carlo
assessment of reliability of sources from the different techniques, an implementation of the PowellSnakes source extraction technique was used
at the five frequencies between 30 and 143 GHz while the SExtractor technique was used between 217 and 857GHz. The 10Ï photometric flux
density limit of the catalogue at |b| > 30⊠is 0.49, 1.0, 0.67, 0.5, 0.33, 0.28, 0.25, 0.47 and 0.82 Jy at each of the nine frequencies between 30
and 857 GHz. Sources which are up to a factor of âŒ2 fainter than this limit, and which are present in âcleanâ regions of the Galaxy where the sky
background due to emission from the interstellar medium is low, are included in the ERCSC if they meet the high reliability criterion. The Planck
ERCSC sources have known associations to stars with dust shells, stellar cores, radio galaxies, blazars, infrared luminous galaxies and Galactic
interstellar medium features. A significant fraction of unclassified sources are also present in the catalogs. In addition, two early release catalogs
that contain 915 cold molecular cloud core candidates and 189 SZ cluster candidates that have been generated using multifrequency algorithms are
presented. The entire source list, with more than 15000 unique sources, is ripe for follow-up characterisation with Herschel, ATCA, VLA, SOFIA,
ALMA and other ground-based observing facilities
Planck early results XXIV : Dust in the diffuse interstellar medium and the Galactic halo
Peer reviewe