85 research outputs found
The extragalactic sources at mm wavelengths and their role as CMB foregrounds
The thesis is divided into three main parts. In the first part we have discussed the characterization of the radio source emission in the high radio frequency band. The second part has been devoted to investigating the Sunyaev-Zel\u2019dovich effect focussing on its observability and on theoretical predictions for proto-galaxies. Finally, in the third part we have dealt with radio sources as a CMB foreground, with special reference to the Planck mission
Advanced European Network of E-infrastructures for Astronomy with the SKA
Here, I present the AENEAS (Advanced European Network of E-infrastructures for Astronomy with the SKA) project has been funded in the Horizon 2020 Work Programme call “Research and Innovation Actions for International Co-operation on high-end e-infrastructure requirements” supporting the Square Kilometre Array (SKA).
INAF is contributing to all the AENEAS working packages and leading the WP5 - Access and Knowledge Creation
(WP leader M. Massardi IRA-ARC), participants from IRA (Brand, Nanni, Venturi) ,OACT(Becciani, Costa, Umana),
OATS (Smareglia, Knapic, Taffoni
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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The Tiered Radio Extragalactic Continuum Simulation (T-RECS)
We present the Tiered Radio Extragalactic Continuum Simulation (T-RECS): a
new simulation of the radio sky in continuum, over the 150 MHz-20 GHz range.
T-RECS models two main populations of radio galaxies: Active Galactic Nuclei
(AGNs) and Star-Forming Galaxies (SFGs), and corresponding sub-populations. Our
model also includes polarized emission over the full frequency range, which has
been characterised statistically for each population using the available
information. We model the clustering properties in terms of probability
distributions of hosting halo masses, and use lightcones extracted from a
high-resolution cosmological simulation to determine the positions of haloes.
This limits the sky area for the simulations including clustering to a 25deg2
field of view. We compare luminosity functions, number counts in total
intensity and polarization, and clustering properties of our outputs to
up-to-date compilations of data and find a very good agreement. We deliver a
set of simulated catalogues, as well as the code to produce them, which can be
used for simulating observations and predicting results from deep radio surveys
with existing and forthcoming radio facilities, such as the Square Kilometre
Array (SKA).Comment: 20 pages, 11 figures, accepted by MNRA
Optical Properties of High-Frequency Radio Sources from the Australia Telescope 20 GHz (AT20G) Survey
Our current understanding of radio-loud AGN comes predominantly from studies
at frequencies of 5 GHz and below. With the recent completion of the Australia
Telescope 20 GHz (AT20G) survey, we can now gain insight into the
high-frequency radio properties of AGN. This paper presents supplementary
information on the AT20G sources in the form of optical counterparts and
redshifts. Optical counterparts were identified using the SuperCOSMOS database
and redshifts were found from either the 6dF Galaxy survey or the literature.
We also report 144 new redshifts. For AT20G sources outside the Galactic plane,
78.5% have optical identifications and 30.9% have redshift information. The
optical identification rate also increases with increasing flux density.
Targets which had optical spectra available were examined to obtain a spectral
classification.
There appear to be two distinct AT20G populations; the high luminosity
quasars that are generally associated with point-source optical counterparts
and exhibit strong emission lines in the optical spectrum, and the lower
luminosity radio galaxies that are generally associated with passive galaxies
in both the optical images and spectroscopic properties. It is suggested that
these different populations can be associated with different accretion modes
(cold-mode or hot-mode). We find that the cold-mode sources have a steeper
spectral index and produce more luminous radio lobes, but generally reside in
smaller host galaxies than their hot-mode counterparts. This can be attributed
to the fact that they are accreting material more efficiently. Lastly, we
compare the AT20G survey with the S-cubed semi-empirical (S3-SEX) models and
conclude that the S3-SEX models need refining to correctly model the compact
cores of AGN. The AT20G survey provides the ideal sample to do this.Comment: Accepted for publication in MNRA
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