6th June 2007
Marsfield Lecture Theatre

Programme

Abstracts
 
 

Annie Hughes, Swinburne University of Technology

HI and CO clouds in the LMC

Observational evidence that molecular clouds have lifetimes of only a few Myr has raised the possibility that molecular clouds may be transient features within large-scale flows in the atomic interstellar gas, rather than well-defined, quasi-equilibrium objects. In this talk, I will present a survey of the 12CO emission from molecular clouds in the Large Magellanic Cloud that we have been conducting with the ATNF Mopra telescope in order to study the relationship between the atomic and molecular gas phases. At 115GHz, the angular resolution of Mopra is well-matched to the angular resolution of the ATCA+PKS HI survey of the LMC (Kim et al. 2003), allowing us to examine the relationship between the two gas phases on physical scales down to ~15pc. I will present the physical and dynamical properties of the molecular clouds in our survey, and discuss how the clouds appear to be related to their surrounding atomic envelopes.
 
 

Emma Kirby, Austalian National University 

Multiwavelength Properties of Local Volume Galaxies

Deep near-IR imaging of 65 Local Volume galaxies has been combined with HI 21cm data and existing optical B data. We determine multiwavelength relations such as the optical-infrared absolute magnitude relation, the HI mass-to-light ratio and the baryonic Tully Fisher relation in the dwarf regime.

Rajan Chhetri, University of New South Wales

Search for Gravitational Lenses using AT20G Data

The use of the AT Compact Array for Australia Telescope 20 GHz (AT20G) Suvey has given us a unique opportunity to look for Gravitational Lenses in the Southern Hemisphere. Gravitational Lenses provide a good indication of mass distribution in the Universe and also provide independent measures of constraining of cosmological parameters like the Hubble Constant. I will be presenting my research by presenting the method we have come up with to look for such lenses and also issues we have come across in the process of doing so.

Jamie McCallum, University of Tasmania

Scintillating Spectra and magnetic fields in Circinus

Shari Breen, University of Tasmania

Water masers within the G333.2-0.6 giant molecular cloud

We report the results of a blind search for 22 GHz water masers in two regions, covering approximately half a square degree, within the giant molecular cloud associated with RCW 106. The complete search of the two regions was carried out with the 26 m Mount Pleasant radio telescope and resulted in the detection of nine water masers, five of which are new detections.  Australia Telescope Compact Array observations of these detections have allowed us to obtain positions with arcsecond accuracy, allowing meaningful comparison with infrared and molecular data for the region.  We find that for the regions surveyed there are more water masers than either 6.7 GHz methanol, or main-line OH masers.  The water masers are concentrated towards the central axis of the star formation region, in contrast to the 6.7 GHz methanol masers which tend to be located near the periphery.  The colours of the GLIMPSE point sources associated with the water masers are similar to those of 6.7 GHz methanol masers, but slightly less red.  We have made a statistical investigation of the properties of the 13CO and 1.2 mm dust clumps with and without associated water masers.  We find that the water masers are associated with the more massive, denser and brighter 13CO and 1.2 mm dust clumps.  We present statistical models that are able to predict those 13CO and 1.2 mm dust clumps that are likely to have associated water masers, with a low misclassification rate.

Douglas Hayman, Macquarie University

Focal Plane Array Development with the Marsfield Interferometer

A two dish interferometer has been built at the CSIRO Marsfield site to investigate phased array feed technologies for the next generation of radio telescopes, including MIRANdA and the SKA. Phased array feeds consisting of densely spaced focal plane arrays have the potential to provide contiguous wide fields of view and hence can greatly increase survey speeds. This interferometer is being used to investigate beamforming and calibration techniques. This talk will describe the instrument, some of the challenges in its development, proposed experiments and if available in time, some results.

Martin Leung, University of Sydney

Wideband Dual Polarised Line Feed Development for a Cylindrical Reflector
Radio Telescope

Development of a new wideband dual polarised line feed is an integral part of the planned Square Kilometre Array Molonglo Project (SKAMP) upgrade to the Molonglo Observatory Synthesis Telescope (MOST). The feed will expand the existing MOST observation frequency range, enable polarimetric imaging and improve its system sensitivity. In this talk I will discuss the engineering design and performance of a line feed prototype for the SKAMP upgrade.

Daniel Yardley, University of Sydney

Searching for Correlations in Data from the Parkes Pulsar Timing Array

The use of a pulsar timing array such as the PPTA enables the detection (via correlation) of a variety of phenomena that influence pulsar timing residuals. These include clock irregularities, errors in the solar system ephemeris and possibly a gravitational wave background. These effects should have different angular signatures distributed across the sky. This talk will describe the process of detection of gravitational waves and clock irregularities, with reference to some basic statistical methods required.

Adam Deller, Swinburne University of Technology

Sub-mas pulsar astrometry with the Long Baseline Array (LBA)

Very Long Baseline Interferometry (VLBI) offers the opportunity to make measurements of pulsar distances and transverse velocities, tied to the fundamental International Celestial Reference Frame (ICRF), via astrometric measurements.  Obtaining reliable pulsar distances is crucial for a range of scientific goals, from tests of general relativity to the pulsar luminosity function.  However, pulsars are challenging targets for VLBI and to date only 2 VLBI parallaxes have been obtained in the South. In this presentation I will outline my current LBA astrometric program of eight pulsars, and present preliminary results.

Leith Godfrey, Australian National University

A Multi-Wavelength Study of the Extremely Luminous VLBI-Scale Hotspot of PKS 1421-490

Using the Australian Long Baseline Array, we have obtained an exquisite high resolution image of the North-Eastern Hotspot of PKS 1421-490. The hotspot is very compact (400pc across) given its extreme luminosity, and exhibits a smooth surface brightness distribution. A protrusion at the leading edge of the hotspot resembles the morphology expected from the 'dentist drill effect'.
By combining our VLBI data with single dish fluxes for this source, we are able to constrain the low energy cutoff in the electron energy spectrum. A one-zone synchrotron self Compton model provides a good fit to the radio, optical and X-ray flux and yields a robust estimate of the magnetic field strength and electron density within the hotspot. I will discuss our findings and the implications of these results for the interpretation of hotspot X-ray emission.

Cliff Senkbeil, University of Tasmania

The VLBI Position Stability of Interstellar Scintillating Active Galactic Nuclei

Interstellar Scintillation (ISS) has become a widely accepted explanation for Active Galactic Nuclei (AGN) variability on timescales of days to just a few hours. Flat Spectrum ISS sources which are compact at micro-arcsecond scales, as a population, have better 8.4 GHz radio position stability than non-scintillating flat-spectrum sources. The International Celestial Reference Frame (ICRF) ties in with other systems used for navigation, such as the International Terrestrial Reference Frame and the Earth Orientation Parameters. The ICRF utilises the radio positions of distant AGN to define the reference frame. Sources used to define the reference frame must have a stable milli-arcsecond structure to prevent local deformation. The compact structure of scintillating radio sources make them ideal for defining the ICRF.

David Jones, University of Adelaide

G333.125-0.562: a massive star forming region at a very early evolutionary stage?

Massive star formation is a great mystery in astrophysics. In particular, how similar is it to low and intermediate mass (M <~10 M_sun) star formation?  Over the past 20 or so years, advances in imaging has led to an increase in observational data on sites of massive star formation, and has shown that there could be some parallels with low mass star formation, such as accretion disks. However, stars with suffiecient luminosity can reverse any accretive process, making a direct scaling implausible.  Also, due to the expected short timescales of the formation of a protostellar object (s) and indeed a main sequence star, which are expected to affect their environment soon after formation, observations of dense clouds yet to form a stellar object(s) have proved elusive.  I report on ATCA observations at 20 and 13 cm in coincidence with archival 3.6 cm ATCA observations of G333.125-0.562, a massive, dense, cold core which is not observed at infrared wavelengths.  Is this an example of a cloud which will go on to form massive stars, or has it already done so?