50 research outputs found
Enabling Deliberations in a Political Party Using Large-Scale Argumentation: A Preliminary Reports
This paper represents a preliminary report on using an argumentation system to enable large scale deliberations, involving over 400 members of the Italian Democratic Party, on electoral law reform. It is, to our knowledge, one of very few evaluations of large-scale argumentation, as well as the first to include a systematic comparison with conventional (web forum based) online deliberation. We will discuss (1) the strengths and limitations of current deliberation technologies, (2) how large-scale argumentation technology can help address these limitations, and (3) preliminary results from the Democratic Party evaluation of this technology
Representations of Time Coordinates in FITS
In a series of three previous papers, formulation and specifics of the
representation of World Coordinate Transformations in FITS data have been
presented. This fourth paper deals with encoding time. Time on all scales and
precisions known in astronomical datasets is to be described in an unambiguous,
complete, and self-consistent manner. Employing the well--established World
Coordinate System (WCS) framework, and maintaining compatibility with the FITS
conventions that are currently in use to specify time, the standard is extended
to describe rigorously the time coordinate. World coordinate functions are
defined for temporal axes sampled linearly and as specified by a lookup table.
The resulting standard is consistent with the existing FITS WCS standards and
specifies a metadata set that achieves the aims enunciated above.Comment: FITS WCS Paper IV: Time. 27 pages, 11 table
The HIPASS survey of the Galactic plane in Radio Recombination Lines
We present a Radio Recombination Line (RRL) survey of the Galactic Plane from
the HI Parkes All-sky Survey and associated Zone of Avoidance survey, which
mapped the region l=196degr -- 0degr --52degr and |b| < 5degr at 1.4 GHz and
14.4 arcmin resolution. We combine three RRLs, H168, H167, and
H166 to derive fully sampled maps of the diffuse ionized emission along
the inner Galactic plane. The velocity information, at a resolution of 20 km/s,
allows us to study the spatial distribution of the ionized gas and compare it
with that of the molecular gas, as traced by CO. The longitude-velocity diagram
shows that the RRL emission is mostly associated with CO gas from the molecular
ring and is concentrated within the inner 30degr of longitude. A map of the
free-free emission in this region of the Galaxy is derived from the
line-integrated RRL emission, assuming an electron temperature gradient with
Galactocentric radius of K/kpc. Based on the thermal continuum map
we extracted a catalogue of 317 compact (<15 arcmin) sources, with flux
densities, sizes and velocities. We report the first RRL observations of the
southern ionized lobe in the Galactic centre. The line profiles and velocities
suggest that this degree-scale structure is in rotation. We also present new
evidence of diffuse ionized gas in the 3-kpc arm. Helium and carbon RRLs are
detected in this survey. The He line is mostly observed towards HII regions,
whereas the C line is also detected further away from the source of ionization.
These data represent the first observations of diffuse C RRLs in the Galactic
plane at a frequency of 1.4 GHz.Comment: 20 pages, 14 figures. MNRAS accepte
The Australia Telescope 20GHz (AT20G) Survey: analysis of the extragalactic source sample
The Australia Telescope 20 GHz (AT20G) survey is a blind survey of the whole
Southern sky at 20 GHz with follow-up observations at 4.8, 8.6, and 20 GHz
carried out with the Australia Telescope Compact Array (ATCA). In this paper we
present an analysis of radio spectral properties in total intensity and
polarisation, sizes, optical identifications, and redshifts of the sample of
the 5808 extragalactic sources in the survey catalogue of confirmed sources
over the whole Southern sky excluding the strip at Galactic latitude
|b|<1.5deg. The sample has a flux density limit of 40 mJy. Completeness has
been measured as a function of scan region and flux density. Averaging over the
whole survey area the follow-up survey is 78% complete above 50mJy and 93%
complete above 100mJy. 3332 sources with declination <-15deg have good quality
almost simultaneous observations at 4.8, 8.6, and 20GHz. The spectral analysis
shows that the sample is dominated by flat-spectrum sources. The fraction of
flat-spectrum sources decreases from 81% for 20GHz flux densities S>500mJy, to
60% for S<100mJy. There is also a clear spectral steepening at higher
frequencies with the median spectral index decreasing from -0.16 between 4.8
and 8.6GHz to -0.28 between 8.6 and 20GHz. Simultaneous observations in
polarisation are available for all the sources at all the frequencies. 768
sources have a good quality detection of polarised flux density at 20GHz; 467
of them were also detected in polarisation at 4.8 and/or at 8.6GHz so that it
has been possible to compare the spectral behaviour in total intensity and
polarisation. We have found that the polarised fraction increases slightly with
frequency and decreases with flux density. Cross matches and comparisons have
been made with other catalogues at lower radio frequencies, and in the optical,
X-ray and gamma-ray bands. Redshift estimates are available for 825 sources.Comment: 15 pages, 16 figures, accepted for publication in MNRA
The Australia Telescope 20 GHz Survey: The Source Catalogue
We present the full source catalogue from the Australia Telescope 20 GHz
(AT20G) Survey. The AT20G is a blind radio survey carried out at 20 GHz with
the Australia Telescope Compact Array (ATCA) from 2004 to 2008, and covers the
whole sky south of declination 0 deg. The AT20G source catalogue presented here
is an order of magnitude larger than any previous catalogue of high-frequency
radio sources, and includes 5890 sources above a 20 GHz flux-density limit of
40 mJy. All AT20G sources have total intensity and polarisation measured at 20
GHz, and most sources south of declination -15 deg also have near-simultaneous
flux-density measurements at 5 and 8 GHz. A total of 1559 sources were detected
in polarised total intensity at one or more of the three frequencies. We detect
a small but significant population of non-thermal sources that are either
undetected or have only weak detections in low-frequency catalogues. We
introduce the term Ultra-Inverted Spectrum (UIS) to describe these radio
sources, which have a spectral index alpha(5, 20) > +0.7 and which constitute
roughly 1.2 per cent of the AT20G sample. The 20 GHz flux densities measured
for the strongest AT20G sources are in excellent agreement with the WMAP 5-year
source catalogue of Wright et al. (2009), and we find that the WMAP source
catalogue is close to complete for sources stronger than 1.5 Jy at 23 GHz.Comment: 21 pages, accepted for publication in MNRA
The Australia Telescope 20GHz Survey: Hardware, Observing Strategy, and Scanning Survey Catalog
The Australia Telescope 20GHz (AT20G) survey is a large area (2{\pi} sr),
sensitive (40mJy), high frequency (20GHz) survey of the southern sky. The
survey was conducted in two parts: an initial fast scanning survey, and a
series of more accurate follow-up observations. The follow-up survey catalog
has been presented by Murphy et al. 2010. In this paper we discuss the hardware
setup and scanning survey strategy as well as the production of the scanning
survey catalog.Comment: 32 pages, 20 figures, accepted for publication in experimental
astronom
A derivation of the free-free emission on the Galactic plane between l=20 and 44 degrees
We present the derivation of the free-free emission on the Galactic plane
between l=20 and 44 degrees and |b| < 4 degrees, using Radio Recombination Line
(RRL) data from the HI Parkes All-Sky Survey (HIPASS). Following an upgrade on
the RRL data reduction technique, which improves significantly the quality of
the final RRL spectra, we have extended the analysis to three times the area
covered in Alves et al. (2010). The final RRL map has an angular resolution of
14.8 arcmin and a velocity resolution of 20 km/s.
A map of the electron temperature (Te) of the ionised gas is derived for the
area under study using the line and continuum data from the present survey. The
mean Te on the Galactic plane is 6000 K. The first direct measure of the
free-free emission is obtained based on the derived Te map. Subtraction of this
thermal component from the total continuum leaves the first direct measure of
the synchrotron emission at 1.4 GHz. A narrow component of width 2 degrees is
identified in the latitude distribution of the synchrotron emission. We present
a list of HII regions and SNRs extracted from the present free-free and
synchrotron maps, where we confirm the synchrotron nature of three objects:
G41.12-0.21, G41.15+0.39 and G35.59-0.44. We also identify a bright (42 Jy) new
double radio galaxy, J1841-0152, previously unrecognised owing to the high
optical extinction in the region.
The latitude distribution for the RRL-derived free-free emission shows that
the WMAP Maximum Entropy Method (MEM) is too high by ~ 50 per cent, in
agreement with other recent results. The extension of this study to the inner
Galaxy region l=-50 to 50 degrees will allow a better overall comparison of the
RRL result with WMAP.Comment: 17 pages, 15 figures. Submitted to MNRA