16th June 2009
Marsfield Lecture Theatre

Programme

Abstracts
 
 

Keith Bannister, University of Sydney

A 12-Year, Southern Sky Survey for Radio Variability and Transients using MOST

A 12-Year, Southern Sky Survey for Radio Variability and Transients using MOST The Molonglo Observatory Synthesis Telescope (MOST) has been imaging the southern skies at 843 MHz since 1996. Data were taken as part of major surveys (MGPS-1, SUMSS, MGPS-2), as part of monitoring campaigns, and towards specific targets of interest. The resulting sets of images now cover some parts of the sky multiple times, and with a range of candences. This data-set provides an unprecedented opportunity to characterise the variable sky at 843 MHz on time scales ranging from one day to many years. I will present an overview of the MOST archive and our identification algorithms along with the resulting discovery of more than 40 slowly varying radio sources in the southern sky. I will conclude by discussing some of the techniques and pitfalls of variable and transient detection, as will need to be addressed for ASKAP, SKAMP and other future radio surveys.
 
 

Jay Blanchard, University of Tasmania 

Linking the Radio and Gamma Ray Properties of Blazars

The mechanism for the production of gamma rays in blazars is as yet poorly understood. Current theory suggests upscattering of photons via the inverse Compton effect, however the details of the photon and electron populations involved are unclear. With the launch of Fermi, NASAs new gamma ray space observatory, comes an opportunity to study a large number of gamma ray blazars in much greater detail (especially in the time domain) than was previously possible. The project presented here involves the use of several radio telescopes to monitor these sources, complementing the Fermi data. Studying the relationship between (for example) flaring observed in the gamma ray part of the spectrum and similiar behaviour in the radio gives information on the possible emission sites of the gamma rays and hence the mechanisms involved in their generation.

Justin Bray, University of Adelaide

Searching for ultra-high-energy neutrinos using radio telescopes

The existence of ultra-high-energy (UHE) neutrinos is predicted from models of the propagation of UHE cosmic rays, but they have not yet been detected. In order to remedy this, the ATCA and Parkes telescopes have been employed to look for the nanosecond-scale radio pulses that should be produced when these neutrinos interact in the upper layers of the Moon. This project aims to improve models of the efficacy of this technique, and to determine the extent to which it limits predictions of the UHE neutrino flux.

Sarah Burke-Spoloar, Swinburne

Things that buzz, beep, and whistle in the radio sky

This will be a general presentation of the discoveries in a search for bright, single pulsations lasting under one second in archival radio pulsar data. It will outline how the search is done, the various types of exciting astrophysical events which emit pulsations on such a short timescale, and then present the discoveries made in the data; these include a "schizophrenic" pulsar, several RRATs, and a highly dispersed transient whose origin yet eludes us.

Chris Hales, University of Sydney

Cosmic Shades: Radio Polarimetry and Large Scale Magnetic Fields

The origin and evolution of large scale magnetic fields in the Universe remain poorly constrained by observational data. In an effort to address this, I am using the Australia Telescope Large Area Survey (ATLAS) to investigate magnetic fields in an ensemble of radio galaxies that extend to beyond z~2. I will present the deepest probe to date of the polarised sky using ATLAS observations at 1420 MHz, to a minimum rms noise level of ~18 microjanskys per beam in stokes Q and U. This will form part of a longer-term project to measure the as-yet unknown magnetic power spectrum of the intercluster medium.

Lina Levin, Swinburne

The High Time Resolution Universe - A new digital all-sky survey for pulsars

All of the large-scale pulsar surveys to date have had their sensitivities compromised by the dispersive properties of the interstellar medium. The High Time Resolution Universe project will search for pulsars and fast transient sources, using the 20-cm multibeam receiver at Parkes Observatory in the first uniform digital all-sky survey of the Galaxy. It will use digital spectrometers to greatly enhance frequency and time resolution, and increase the dynamic range compared to earlier surveys. This Petabyte record of the radio sky should reveal the true distribution of radio pulsars in the Galaxy, and is expected to find around 500 new slow and 130 new millisecond pulsars, plus be much more sensitive to transients.

Elizabeth Mahony, University of Sydney

Radio properties of X-ray selected QSOs

QSOs are often classified into two broad categories - radio-loud and radio-quiet, but the underlying distribution of radio luminosity in QSOs and Type 1 AGN has long been debated in the literature. There are two opposing views; the first is that the distribution of radio-loudness is bimodal, i.e. there are distinct radio-loud and radio-quiet populations. The second view is that there is a broad, continuous distribution which includes one or more intermediate classes of objects. By obtaining high frequency radio data for a large sample of X-ray selected QSOs, we can provide a definitive test of the possible bimodality in the radio properties of the z

Minnie Mao, University of Tasmania

WAT Cluster?

Wide-Angle Tail (WAT) radio sources are radio galaxies whose jets are bent back in a common direction. They are known to trace dense regions of the IGM and are used as probes or tracers for clusters of galaxies. One such WAT, identified in the ATLAS 1.4 GHz survey, is associated with a strong redshift-space over-density at z~0.2. The WAT is also in close proximity (

Stephan Oslowski, Swinburne

High precision pulsar timing and the formation and evolution of binary pulsars

Pulsar timing is methodology that leads to majority of pulsar astrophysics. Our timing has improved over years but we are still far away from the theoretical limits of timing precision. My work is primarily concerned with using the next generation of instrumentation to increase the accuracy of pulsar timing, relate it to binary pulsar origin and evolution in the first instance and contribute to longer term goal of detecting gravitational waves through investigation and removal of systematic errors.

Attila Popping, Kapteyn Astronomical Institute

Deep HI Observations: searching the Cosmic Web.

Galaxies do not dominate the universal baryon budget, but are the brightest pearls of an underlying Cosmic Web. Large gaseous filaments extending between the massive galaxies are a prediction of numerical simulations. Due to the moderately high temperature in the intergalactic medium, most of the gas in the Cosmic Web is highly ionised. Very deep HI observations are required, to detect the neutral component of the Cosmic Web. I will present some results from data obtained with the WSRT in a very peculiar observing mode. With an HI column density sensitivity of ~10^18 cm^-2, we can detect diffuse emission, that has not been seen before.

Kate Randall, University of Sydney

CSS and GPS sources

Compact Steep Spectrum (CSS) and Gigahertz Peaked Spectrum (GPS) sources are a class of compact, powerful, extragalactic objects, which are not well understood. They comprise a large percentage of the bright centimetre wavelength radio sources, and likely a similar percentage at faint flux densities. CSS and GPS sources exhibit a steep spectrum, with GPS objects having a spectral turnover at around 1 GHz. A typical CSS or GPS source has small scale radio lobes or jets on either side of the central core, likely an AGN. Although many surveys and studies have explored CSS and GPS sources, particularly in the Northern Hemisphere, their exact position in galaxy evolutionary schemes is still uncertain. Several theories exist as to how these objects evolve, and it is generally considered that CSS and GPS sources evolve into large scale radio sources, such as FR-I/II galaxies. I present here results of radio observations, and part of the analysis done on these objects as a side project within my PhD, in particular some interesting outcomes, and details on a few intriguing sources.

Urvashi Rau, Socorro, NMT/NRAO

Wide-Field Wide-Band Imaging in Radio Interferometry

New broad-band receivers are being installed on several existing and new radio interferometers. The technique of multi-frequency-synthesis (MFS) is expected to be used to increase the instantaneous uv-coverage of the array and to achieve maximum sensitivity during imaging. However, across these wide bandwidths, the spectral structure of the sky brightness can become significant and must be accounted for during imaging. Also, the antenna field-of-view changes with frequency, and his has implications for wide-field and mosaic imaging. In this talk I will present results from a new algorithm that improves upon existing MFS imaging techniques to account for these effects.

Rob R, University of Adelaide

Unmasking the Dark Accelerator

For the better part of the last 100 years cosmic ray researchers have climbed mountains, ventured aloft in hot air balloons and set up vast experiments in far-flung corners of the world in an effort to understand the source of these highly relativistic particles from space. The latest generation of ground-based Cherenkov telescopes have highlighted numerous candidates including supernova remnants, microquasars, pulsars and associated pulsar wind nebulae. More mysteriously, a subset of enigmatic sources with undetected counterparts at other wavelengths has raised the possibility of the existence of a new class of 'dark' particle accelerators. Is it possible to use radio telescopes to track them down -- and what other discoveries are there to be made along the way?

Max Spoloar, Swinburne

TBD

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Marion Wienen, Max-Planck-Institut fur Radioastronomie

TBD

The initial conditions of molecular clumps, in which massive stars form, are still poorly known in contrast to considerable advances, that have been made in the understanding of early stages of low-mass star formation. In particular, progress has to be made in the investigation of the phases before ultracompact HII regions have formed and the newly formed massive (proto) stars emerge in the infrared. These phases are best searched for and detected by (sub)millimeter dust continuum and high-density molecular tracers. Especially ammonia is a good estimator for the temperature and kinematics of cold and dense molecular clumps. Using the Effelsberg 100-m telescope, the ammonia line emission was therefore investigated towards a dust-selected sample of massive molecular clumps, which have newly been detected in ATLASGAL, the first unbiased submillimeter survey of the Galactic Plane. The results of this large ammonia sample of high-mass star forming clumps will be presented and derived physical parameters discussed.

Daniel Yardley, University of Sydney

Detecting the Gravitational Wave Background Using a Pulsar Timing Array

We present results from the first analysis of the correlations present in data from a pulsar timing array. The pulsar timing data were mostly taken with the Parkes Radio Telescope, with recent observations taken as part of the Parkes Pulsar Timing Array project. We hope to obtain the most stringent limit to date on the amplitude of the isotropic stochastic gravitational-wave background using a new technique, and hope to be able to rule out some predictions for the background. This will have important implications for popular theories of galaxy evolution.