D. McConnell

The Australia Telescope Compact Array Broad-band Backend: description and first results

Here we describe the Compact Array Broadband Backend (CABB) and present first results obtained with the upgraded Australia Telescope Compact Array (ATCA). The 16-fold increase in observing bandwidth, from 2×128 MHz to 2×2048 MHz, high bit sampling, and addition of 16 zoom windows (each divided into a further 2048 channels) provide major improvements for all ATCA observations. The benefits of the new system are: (1) hugely increased radio continuum and polarization sensitivity as well as image fidelity, (2) substantially improved capability to search for and map emission and absorption lines over large velocity ranges, (3) simultaneous multi-line and continuum observations, (4) increased sensitivity, survey speed and dynamic range due to high-bit sampling, and (5) high velocity resolution, while maintaining full polarization output. The new CABB system encourages all observers to make use of both spectral line and continuum data to achieve their full potential. Given the dramatic increase of the ATCA capabilities in all bands (ranging from 1.1 to 105 GHz) CABB enables scientific projects that were not feasible before the upgrade, such as simultaneous observations of multiple spectral lines, on-the-fly mapping, fast follow-up of radio transients (e.g., the radio afterglow of new supernovae) and maser observations at high velocity resolution and full polarization. The first science results presented here include wide-band spectra, high dynamic-range images, and polarization measurements, highlighting the increased capability and discovery potential of the ATCA.

The Australian Square Kilometre Array Pathfinder: System Architecture and Specifications of the Boolardy Engineering Test Array

This paper describes the system architecture of a newly constructed radio telescope - the Boolardy Engineering Test Array, which is a prototype of the Australian Square Kilometre Array Pathfinder telescope. Phased array feed technology is used to form multiple simultaneous beams per antenna, providing astronomers with unprecedented survey speed. The test array described here is a 6-antenna interferometer, fitted with prototype signal processing hardware capable of forming at least 9 dual-polarisation beams simultaneously, allowing several square degrees to be imaged in a single pointed observation. The main purpose of the test array is to develop beamforming and wide-field calibration methods for use with the full telescope, but it will also be capable of limited early science demonstrations.

The 2000 periastron passage of PSR B1259–63

We report here on a sequence of 28 observations of the binary pulsar system PSR B1259−63/SS2883 at four radio frequencies made with the Australia Telescope Compact Array around the time of the 2000 periastron passage. Observations made on 2000 September 1 show that the apparent rotation measure (RM) of the pulsar reached a maximum of −14800 ± 1800 rad m −2 , some 700 times the value measured away from periastron, and is the largest astrophysical RM measured. This value, combined with the dispersion measure, implies a magnetic field in the wind of the Be star of 6 mG. We find that the light curve of the unpulsed emission is similar to that obtained during the 1997 periastron but that differences in detail imply that the emission disc of the Be star is thicker and/or of higher density. The behaviour of the light curve at late times is best modelled by the adiabatic expansion of a synchrotron bubble formed in the pulsar/disc interaction. The expansion rate of the bubble ∼12 km s −1 is surprisingly low but the derived magnetic field of 1.6 G close to that expected.

The radio nebula surrounding the Vela pulsar

We have discovered that the radio nebula surrounding the Vela pulsar covers a much wider extent than previously reported, with two lobes to the North and South of the pulsar. Indications of this object have been reported previously, but its symmetric morphology around the pulsar and other details had not been identified as they were hidden due to poor sensitivity to low spatial frequencies. The structure is highly polarised and the polarisation vectors, once corrected for Faraday rotation, reveal symmetry with respect to the spin axis of the pulsar. The X-ray emission found by Chandra lies at the centre of this structure, in a region which has no detectable excess of radio emission. We estimate total fluxes and regional fluxes from the Northern and Southern lobes, plus the X-ray region at four radio frequencies; 1.4, 2.4, 5 and 8.5 GHz. We present the corresponding images in both the total and polarised intensities, as well as those showing the derotated linear polarisation vectors.

MEASUREMENT OF A MAGNETIC FIELD IN A LEADING ARM HIGH-VELOCITY CLOUD

Using a recent catalog of extragalactic Faraday rotation derived from the NRAO VLA Sky Survey we have found an agreement between Faraday rotation structure and the H I emission structure of a high-velocity cloud (HVC) associated with the Leading Arm of the Magellanic System. We suggest that this morphological agreement is indicative of Faraday rotation through the HVC. Under this assumption we have used 48 rotation measures through the HVC, together with estimates of the electron column density from Hα measurements and QSO absorption lines to estimate a strength for the line-of-sight component of the coherent magnetic field in the HVC of B ∥ 6 μG. A coherent magnetic field of this strength is more than sufficient to dynamically stabilize the cloud against ram pressure stripping by the Milky Way halo and may also provide thermal insulation for the cold cloud. We estimate an upper limit to the ratio of random to coherent magnetic field of Br /B ∥ < 0.8, which suggests that the random field does not dominate over the coherent field as it does in the Magellanic Clouds from which this HVC likely originates.

ASKAP HI imaging of the galaxy group IC 1459

We present HI imaging of the galaxy group IC 1459 carried out with six antennas of the Australian SKA Pathfinder equipped with phased-array feeds. We detect and resolve HI in eleven galaxies down to a column density of

The radio luminosity distribution of pulsars in 47 Tucanae

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Wide-field broad-band radio imaging with phased array feeds: a pilot multi-epoch continuum survey with ASKAP-BETA

cm

The Parkes Galactic Meridian Survey: observations and CMB polarization foreground analysis: PGMS: observations and CMB foregrounds

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GMIMS: the Global Magneto-Ionic Medium Survey

inside a ~6 deg