208 research outputs found
The Use of New Technologies for Improving Reading Comprehension
Since the introduction of writing systems, reading comprehension has always been a foundation for achievement in several areas within the educational system, as well as a prerequisite for successful participation in most areas of adult life. The increased availability of technologies and web-based resources can be a really valid support, both in the educational and clinical field, to devise training activities that can also be carried out remotely. There are studies in current literature that has examined the efficacy of internet-based programs for reading comprehension for children with reading comprehension difficulties but almost none considered distance rehabilitation programs. The present paper reports data concerning a distance program Cloze, developed in Italy, for improving language and reading comprehension. Twenty-eight children from 3rd to 6th grade with comprehension difficulties were involved. These children completed the distance program for 15\u201320 min for at least three times a week for about 4 months. The program was presented separately to each child, with a degree of difficulty adapted to his/her characteristics. Text reading comprehension (assessed distinguishing between narrative and informative texts) increased after intervention. These findings have clinical and educational implications as they suggest that it is possible to promote reading comprehension with a distance individualized program, avoiding the need for the child displacements, necessary for reaching a rehabilitation center
Detailed study of the microwave emission of the supernova remnant 3C 396
We have observed the supernova remnant 3C~396 in the microwave region using
the Parkes 64-m telescope. Observations have been made at 8.4 GHz, 13.5 GHz,
and 18.6 GHz and in polarisation at 21.5 GHz. We have used data from several
other observatories, including previously unpublished observations performed by
the Green Bank Telescope at 31.2 GHz, to investigate the nature of the
microwave emission of 3C 396. Results show a spectral energy distribution
dominated by a single component power law emission with . Data do not favour the presence of anomalous microwave emission coming
from the source. Polarised emission at 21.5 GHz is consistent with
synchrotron-dominated emission. We present microwave maps and correlate them
with infrared (IR) maps in order to characterise the interplay between thermal
dust and microwave emission. IR vs. microwave TT plots reveal poor correlation
between mid-infrared and microwave emission from the core of the source. On the
other hand, a correlation is detected in the tail emission of the outer shell
of 3C 396, which could be ascribed to Galactic contamination.Comment: published in MNRA
Ghost of a Shell: Magnetic Fields of Galactic Supershell GSH 006157
We identify a counterpart to a Galactic supershell in diffuse radio
polarisation, and use this to determine the magnetic fields associated with
this object. GSH 006157 has perturbed the polarised emission at
2.3GHz, as observed in the S-band Polarisation All Sky Survey (S-PASS),
acting as a Faraday screen. We model the Faraday rotation over the shell, and
produce a map of Faraday depth over the area across it. Such models require
information about the polarised emission behind the screen, which we obtain
from the Wilkinson Microwave Anisotropy Probe (WMAP), scaled from 23GHz to
2.3GHz, to estimate the synchrotron background behind GSH 006157.
Using the modelled Faraday thickness we determine the magnitude and the
plane-of-the-sky structure of the line-of-sight magnetic field in the shell. We
find a peak line-of-sight field strength of G. Our measurement probes weak magnetic fields
in a low-density regime (number densities of cm) of the ISM,
thus providing crucial information about the magnetic fields in the
partially-ionised phase.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical
Society. 19 pages, 19 figure
A radio-polarisation and rotation measure study of the Gum Nebula and its environment
The Gum Nebula is 36 degree wide shell-like emission nebula at a distance of
only 450 pc. It has been hypothesised to be an old supernova remnant, fossil
HII region, wind-blown bubble, or combination of multiple objects. Here we
investigate the magneto-ionic properties of the nebula using data from recent
surveys: radio-continuum data from the NRAO VLA and S-band Parkes All Sky
Surveys, and H-alpha data from the Southern H-Alpha Sky Survey Atlas. We model
the upper part of the nebula as a spherical shell of ionised gas expanding into
the ambient medium. We perform a maximum-likelihood Markov chain Monte-Carlo
fit to the NVSS rotation measure data, using the H-halpha data to constrain
average electron density in the shell . Assuming a latitudinal background
gradient in RM we find , angular radius
, shell thickness
, ambient magnetic field strength
and warm gas filling factor
. We constrain the local, small-scale (~260 pc)
pitch-angle of the ordered Galactic magnetic field to
, which represents a significant
deviation from the median field orientation on kiloparsec scales
(~-7.2). The moderate compression factor X=6.0\,^{+5.1}_{-2.5} at
the edge of the H-alpha shell implies that the 'old supernova remnant' origin
is unlikely. Our results support a model of the nebula as a HII region around a
wind-blown bubble. Analysis of depolarisation in 2.3 GHz S-PASS data is
consistent with this hypothesis and our best-fitting values agree well with
previous studies of interstellar bubbles.Comment: 33 pages, 16 figures. Accepted by The Astrophysical Journa
Radio haloes in nearby galaxies modelled with 1D cosmic-ray transport using SPINNAKER
We present radio continuum maps of 12 nearby (), edge-on
(), late-type spiral galaxies mostly at and 5 GHz,
observed with the Australia Telescope Compact Array, Very Large Array,
Westerbork Synthesis Radio Telescope, Effelsberg 100-m and Parkes 64-m
telescopes. All galaxies show clear evidence of radio haloes, including the
first detection in the Magellanic-type galaxy NGC 55. In 11 galaxies, we find a
thin and a thick disc that can be better fitted by exponential rather than
Gaussian functions. We fit our SPINNAKER (SPectral INdex Numerical Analysis of
K(c)osmic-ray Electron Radio-emission) 1D cosmic-ray transport models to the
vertical model profiles of the non-thermal intensity and to the non-thermal
radio spectral index in the halo. We simultaneously fit for the advection speed
(or diffusion coefficient) and magnetic field scale height. In the thick disc,
the magnetic field scale heights range from 2 to 8 kpc with an average across
the sample of ; they show no correlation with either
star-formation rate (SFR), SFR surface density () or rotation
speed (). The advection speeds range from 100 to and display correlations of and
; they agree remarkably well with the
escape velocities (), which can be explained by
cosmic-ray driven winds. Radio haloes show the presence of disc winds in
galaxies with
that extend over several kpc and are driven by processes related to the
distributed star formation in the disc.Comment: 39 pages, 20 colour figures, 10 tables. Accepted by MNRA
S-band Polarization All Sky Survey (S-PASS): survey description and maps
We present the S-Band Polarization All Sky Survey (S-PASS), a survey of
polarized radio emission over the southern sky at Dec~ taken with
the Parkes radio telescope at 2.3~GHz. The main aim was to observe at a
frequency high enough to avoid strong depolarization at intermediate Galactic
latitudes (still present at 1.4 GHz) to study Galactic magnetism, but low
enough to retain ample Signal-to-Noise ratio (S/N) at high latitudes for
extragalactic and cosmological science. We developed a new scanning strategy
based on long azimuth scans, and a corresponding map-making procedure to make
recovery of the overall mean signal of Stokes and possible, a
long-standing problem with polarization observations. We describe the scanning
strategy, map-making procedure, and validation tests. The overall mean signal
is recovered with a precision better than 0.5\%. The maps have a mean
sensitivity of 0.81 mK on beam--size scales and show clear polarized signals,
typically to within a few degrees of the Galactic plane, with ample S/N
everywhere (the typical signal in low emission regions is 13 mK, and 98.6\% of
the pixels have S/N ). The largest depolarization areas are in the inner
Galaxy, associated with the Sagittarius Arm. We have also computed a Rotation
Measure map combining S-PASS with archival data from the WMAP and Planck
experiments. A Stokes map has been generated, with a sensitivity limited to
the confusion level of 9 mK.Comment: Accepted for publication on MNRAS. Maps are available for download at
the website indicated in the manuscrip
Faraday Tomography of the North Polar Spur: Constraints on the distance to the Spur and on the Magnetic Field of the Galaxy
We present radio continuum and polarization images of the North Polar Spur
(NPS) from the Global Magneto-Ionic Medium Survey (GMIMS) conducted with the
Dominion Radio Astrophysical Observatory 26-m Telescope. We fit polarization
angle versus wavelength squared over 2048 frequency channels from 1280 to 1750
MHz to obtain a Faraday Rotation Measure (RM) map of the NPS. Combining this RM
map with a published Faraday depth map of the entire Galaxy in this direction,
we derive the Faraday depth introduced by the NPS and the Galactic interstellar
medium (ISM) in front of and behind the NPS. The Faraday depth contributed by
the NPS is close to zero, indicating that the NPS is an emitting only feature.
The Faraday depth caused by the ISM in front of the NPS is consistent with zero
at b>50 degree, implying that this part of the NPS is local at a distance of
approximately several hundred parsecs. The Faraday depth contributed by the ISM
behind the NPS gradually increases with Galactic latitude up to b=44 degree,
and decreases at higher Galactic latitudes. This implies that either the part
of the NPS at b<44 degree is distant or the NPS is local but there is a sign
change of the large-scale magnetic field. If the NPS is local, there is then no
evidence for a large-scale anti-symmetry pattern in the Faraday depth of the
Milky Way. The Faraday depth introduced by the ISM behind the NPS at latitudes
b>50 degree can be explained by including a coherent vertical magnetic field.Comment: 9 pages, 8 figures, accepted for publication in ApJ. Some figures
have been degraded to reduce sizes, for a high resolution version, see
http://physics.usyd.edu.au/~xhsun/ms_nps.pd
Foregrounds for observations of the cosmological 21 cm line: I. First Westerbork measurements of Galactic emission at 150 MHz in a low latitude field
We present the first results from a series of observations conducted with the
Westerbork telescope in the 140--160 MHz range with a 2 arcmin resolution aimed
at characterizing the properties of the foregrounds for epoch of reionization
experiments. For the first time we have detected fluctuations in the Galactic
diffuse emission on scales greater than 13 arcmin at 150 MHz, in the low
Galactic latitude area known as Fan region. Those fluctuations have an of
14 K. The total intensity power spectrum shows a power--law behaviour down to
with slope . The detection of
diffuse emission at smaller angular scales is limited by residual point
sources. We measured an confusion noise of 3 mJy beam.
Diffuse polarized emission was also detected for the first time at this
frequency. The polarized signal shows complex structure both spatially and
along the line of sight. The polarization power spectrum shows a power--law
behaviour down to with slope .
The of polarization fluctuations is 7.2 K on 4 arcmin scales. By
extrapolating the measured spectrum of total intensity emission, we find a
contamination on the cosmological signal of K on 5 arcmin scales and a corresponding value
of 18.3 K at the same angular scale. The level of the polarization power
spectrum is K on 5 arcmin scales. Given its exceptionally
bright polarized signal, the Fan region is likely to represent an upper limit
on the sky brightness at moderate and high Galactic latitude.Comment: Minor corrections made to match the final version printed on A&A. A
version with high resolution figures is available at
http://www.astro.rug.nl/~bernardi/FAN/fan.pd
The Global Magneto-Ionic Medium Survey: Polarimetry of the Southern Sky from 300 to 480 MHz
Much data on the Galactic polarized radio emission has been gathered in the
last five decades. All-sky surveys have been made, but only in narrow, widely
spaced frequency bands, and the data are inadequate for the characterization of
Faraday rotation, the main determinant of the appearance of the polarized radio
sky at decimetre wavelengths. We describe a survey of the polarized radio
emission from the Southern sky, aiming to characterize the magneto-ionic
medium, particularly the strength and configuration of the magnetic field. This
work is part of the Global Magneto-Ionic Medium Survey (GMIMS). We have
designed and built a feed and receiver covering the band 300 to 900 MHz for the
CSIRO Parkes 64-m Telescope. We have surveyed the entire sky between
declinations -90 and +20 degrees. We present data covering 300 to 480 MHz with
angular resolution 81' to 45'. The survey intensity scale is absolutely
calibrated, based on measurements of resistors at known temperatures and on an
assumed flux density and spectral index for Taurus A. Data are presented as
brightness temperatures. We have applied Rotation Measure Synthesis to the data
to obtain a Faraday depth cube of resolution 5.9 radians per metre squared,
sensitivity of 60 mK of polarized intensity, and angular resolution 1.35
degrees. The data presented in this paper are available at the Canadian
Astronomy Data Centre.Comment: Accepted for publication in the Astronomical Journal Modified 29th
June 2019 to replace outdated doi: for access to dat
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