137 research outputs found
The Planck-ATCA Co-eval Observations (PACO) project: analysis of radio source properties between 5 and 217 GHz
The Planck-ATCA Co-eval Observations (PACO) project has yielded observations
of 464 sources with the Australia Telescope Compact Array (ATCA) between 4.5
and 40 GHz. The main purpose of the project was to investigate the spectral
properties of mm-selected radio sources at frequencies below and overlapping
with the ESA's Planck satellite frequency bands, minimizing the variability
effects by observing almost simultaneously with the first two Planck all-sky
surveys. In this paper we present the whole catalogue of observations in total
intensity. By comparing PACO with the various measures of Planck Catalog of
Compact Sources (PCCS) flux densities we found the best consistency with the
PCCS "detection pipeline" photometry (DETFLUX) that we used to investigate the
spectral properties of sources from 5 to 217 GHz. Of our sources, 91% have
remarkably smooth spectrum, well described by a double power law over the full
range. This suggests a single emitting region, at variance with the notion that
"flat" spectra result from the superposition of the emissions from different
compact regions, self absorbed up to different frequencies. Most of the objects
show a spectral steepening above 30 GHz, consistent with synchrotron emission
becoming optically thin. Thus, the classical dichotomy between
flat-spectrum/compact and steep-spectrum/extended radio sources, well
established at cm wavelengths, breaks down at mm wavelengths. The mm-wave
spectra do not show indications of the spectral break expected as the effect of
"electron ageing", suggesting young source ages.Comment: 15 pages, 7 figures, accepted for publication in MNRA
The Planck-ATCA Co-eval Observations (PACO) project: the bright sample
The Planck-ATCA Co-eval Observations (PACO) have provided flux density
measurements of well defined samples of AT20G radio sources at frequencies
below and overlapping with Planck frequency bands, almost simultaneously with
Planck observations. We have observed with the Australia Telescope Compact
Array (ATCA) a total of 482 sources in the frequency range between 4.5 and 40
GHz in the period between July 2009 and August 2010. Several sources were
observed more than once. In this paper we present the aims of the project, the
selection criteria, and the observation and data reduction procedures. We also
discuss the data in total intensity for a complete sample of 189 sources with
S(20 GHz)>500 mJy, Galactic latitude |b|>5deg, and declination <-30deg, and
some statistical analysis of the spectral behaviour and variability of this
sample, referred to as the "bright PACO sample". Finally we discuss how these
data could be used to transfer absolute calibrations to ground based telescopes
using the CMB dipole calibrated flux densities measured by the Planck
satellite, and we provide some test fluxes on bright calibrators.Comment: 15 pages, 11 figure. Accepted for publication on MNRAS. Catalogue
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Early evolution of galaxies and of large-scale structure from CMB experiments
Next generation CMB experiments with arcmin resolution will, for free, lay
the foundations for a real breakthrough on the study of the early evolution of
galaxies and galaxy clusters, thanks to the detection of large samples of
strongly gravitationally lensed galaxies and of proto-clusters of dusty
galaxies up to high redshifts. This has an enormous legacy value. High
resolution follow-up of strongly lensed galaxies will allow the direct
investigation of their structure and kinematics up to z~6, providing direct
information on physical processes driving their evolution. Follow-up of
proto-clusters will allow an observational validation of the formation history
of the most massive dark matter halos up to z~4, well beyond the redshift range
accessible via X-ray or SZ measurements. These experiments will also allow a
giant leap forward in the determination of polarization properties of
extragalactic sources, and will provide a complete census of cold dust
available for star formation in the local universe.Comment: Science white paper submitted to the Astro2020 US Decadal Surve
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