10th May 2006
Marsfield Lecture Theatre

Programme

Abstracts
 
 

Deanna Matthews, LaTrobe University

High-Resolution Observations of the Magellanic Stream

The Magellanic Stream consists of a stream of gas stretching from the Magellanic Clouds, extending well into the northern hemisphere. Except for small regions, existing observations of neutral hydrogen (HI) in the Magellanic Stream have only been made at the relatively low Angular resolution of the Parkes telescope (~14 arcmin). We present our initial study on the Magellanic Stream at higher resolution using the Australia Telescope Compact Array (ATCA). We combine our data with recent Parkes data to allow for the first time a detailed HI study of the gas from the Interface Region to a declination of approximately -38 degrees. Over a region of ~250 deg2, we are able to fully image all structures with spatial scales in the range 0.1 to 2 kpc. We present a preliminary analysis of the morphology of the gas distribution.
 
 

Annie Hughes, Swinburne

Molecular and Atomic Gas in Ara OB1

I will report on the progress of our project to investigate the relationship between the atomic and molecular gas phases in the massive star-forming region Ara OB1. Ara OB1 is a massive star-forming region situated a few degrees below the Galactic plane. The region contains a variety of star formation phenomena, including early-type stars, molecular clouds with dense cores, embedded clusters, optical HII regions, and compact sources of radio continuum emission. Low resolution observations of Ara OB1 reveal a thin, clumpy filament of molecular gas extending over a degree to the south-west of the star-forming activity. This filament is coincident with the wall of an HI shell and does not appear to be actively forming stars. Last year, we mapped the 13CO(1-0) emission from approximately half of the Ara OB1 molecular cloud using the Mopra Telescope. ATCA observations of the HI emission in Ara OB1, which have a complementary spatial and velocity resolution to the Mopra data, have also recently been completed. I will present some preliminary analysis of the two datasets, and discuss our future plans for the project.
 
 

TBA

High Energy Astrophysics Using Radio Telescopes

TBA
 
 

Aaron Chippendale, University of Sydney

The Cosmological Reionization Experiment (CoRE)

The Cosmological Reionization Experiment (CoRE) aims to measure the sky spectrum with 1 mK relative accuracy over redshifts of 5.2 to 13.2. Millikelvin accuracy would allow us to detect the predicted all-sky signal with an amplitude of order 20 mK. This presentation gives a status report and discusses the development of our calibration strategy using experimental data from the lab and observational tests at Narrabri
 
 

Katherine Newton-McGee

Depolarization Canals in the Interstellar Medium

Measurements of the Galactic radio polarized background have revealed many complicated structures. This structure is largely caused by Faraday rotation in the ionised foreground ISM. Threaded through this structure is a random pattern of very dark and narrow depolariszation canals. These canals are not associated with any structure in the ISM. I will present my work investigating the nature of these canals and show that our range of frequencies and angular resolution have led us to conclude that these canals are caused by differential Faraday rotation.
 
 

David Jones

Observations of Sgr B2: A possible secondary electron/positron contribution to the FIR-RC correlation via synchrotron radiation?

There is an unexplained correlation between the far-infrared (FIR) and radio continuum (RC) emission in many types of galaxies. Convention says that both FIR and RC are from the same source: Stars evolving (FIR) and dying (RC). However, since this explanation requires completely different physics for the two mechanisms, this correlation is very surprising. We have investigated whether synchrotron radiation from secondary electrons/positrons in molecular clouds may contribute to this correlation. In December 2005, three molecular clouds were observed using the Compact Array. Here I present the results from the analysis of these observations, in particular the observations of the complex molecular cloud region near the galactic centre, Sagittarius B2.
 
 

Clemens Trachternach

Low Surface Brightness Galaxies in the Arecibo HI Strip Survey

Low surface brightness (LSB) galaxies are difficult to detect in optical as well as in HI surveys. Both kind of surveys have different selection effects which leads to different samples. We obtained an optical survey of a region which was initially observed as a part of the Arecibo HI Strip Survey (AHISS, Zwaan et al. 1997). I will show the - for optical surveys - necessary criteria for the sample selection and compare our optically selected galaxy sample with that from the AHISS.
 
 

Joris Verbiest, Swinburne

Long Term Pulsar Timing

Pulsar J0437-4715 is the closest and brightest pulsar in the Southern sky. Therefore it lends itself very well for pulsar timing observations. Thirteen years after its discovery, I will report on how the combination of recent data from state-of-the-art backends can be combined with the decade-long timing history to derive unprecedented accuracies for distance, orbital parameters and masses and can ultimately help in putting limits on the existence of a Gravitational Wave Background (GWB).
 
 

Albert Teoh, Swinburne

A New Generation Baseband Recorder

Although pulsar astronomers have, for the last 40 years, begun to shed some light on numerous questions about pulsars, the ISM and general relativity, many more questions begin to surface as a consequence of these revelations. For instance, very little is known about the pulsar microstructure, the emission mechanism and the ISM. One possible reason for this is the lack of instrumentation available to perform such investigations. A new generation instrument, dubbed APSR, will aim to fill this void and provide astronomers with a better understanding of the ISM and pulsar emission physics.
 
 

Leith Godfrey, Australian National University

The kpc-scale jet of PKS 2101-490 as seen with Chandra, HST and the ATCA

Jets are commonly observed in images of radio galaxies and quasars at radio wavelengths, but until the launch of the Chandra X-ray Observatory, jet detections in the X-ray band were rare. The huge improvement in angular resolution and sensitivity provided by Chandra has enabled the discovery X-ray jets in abundance. Here I will present new Chandra, HST, and ATCA images of an intriguing jet source, PKS 2101-490. I will discuss the results of some preliminary analysis involving the standard "one zone models" for jet emission. However, these "one zone models" may not be applicable. The new data reveal distinct differences between the radio and X-ray emission. In particular, offsets of order 0.4 arcseconds are observed between the local maxima of radio and X-ray emission along the jet, with the X-ray peak located downstream from the associated radio peak. This behaviour has not previously been observed, and if the offsets are confirmed, they may challenge the current interpretations of quasar jet emission.
 
 

Cliff Senkbeil, University of Tasmania

IDV Monitoring at the Hobart and Ceduna Radio Telescopes and the Progress of the fifth MASIV Epoch

Many flat radio spectrum Active Galactic Nuclei (AGN) sources change rapidly in radio intensity on timescales as short as a few hours; a phenomenon referred to as Intraday variability (IDV). The rapid nature of IDV presented radio astronomers with an interesting question, how can such bright radio objects change in brightness so quickly? Many have provided mechanisms by which a radio source can change intensity rapidly without violating the Inverse Compton limit. Many of these mechanisms required exceptional circumstances and could not explain why IDV is so common in flat radio spectrum AGN. A propagation process known as Interstellar Scintillation (ISS) is more successful at describing such variability. ISS occurs when radio waves from a distant object scatter through the local interstellar medium and arrive in the observer plane, where the intensity of the original signal varies in space with a characteristic scale size. The observed variability is caused by the motion of the Earth through the intensity pattern. Physically the variability depends on the angular size of the radio source, the distance from the observer to the scattering medium, the relative proper velocity of the scattering medium and the wavelength of the radio waves observed. ISS allows us to study these objects at resolutions down to micro-arc second scales and also allows the study of the properties of the local interstellar medium. This talk will present observations from the recent MASIV 5 survey, as well as constant monitoring observations from the Ceduna and Hobart Radio Telescopes.