| Home Page | Program | Public Talk | Social Events | Registration | Venue | Accommodation | Transport | Posters | Contact Us |
 
|
|
|
THE ASTRONOMICAL SOCIETY OF AUSTRALIA INC. |
Annual Scientific Meeting 1st to 5th July, 2007 |
| Program |  All Days |
Sunday |
Monday |
Tuesday |
Wednesday |
Thursday |
Posters |
| Abstracts | Posters A-K |
Posters L-Z |
Monday |
Tuesday |
Wednesday |
Thursday |
Lunch Meetings |
Abstracts - Posters: L-Z
Neutral Hydrogen Gas in Star-Forming Galaxies at z=0.24
Philip Lah, Jayaram Chengalur, Frank Briggs, Matthew Colless, Roberto De Propris, Michael Pracey and Erwin de Blok
We are conducting a study of the relationship between neutral gas content and star formation in galaxies as a function of redshift and environment. We have used the Giant Metrewave Radio Telescope (GMRT) to observe 348 H-alpha emitting field galaxies at z=0.24 selected through narrow-band imaging with Subaru. This sample shows the star-formation rate at this redshift is 3 times that at z=0. Deep radio observations with GMRT (44 hours in total) were obtained with GMRT, while redshifts were obtained with AAOmega for a subsample of 121 galaxies. The correlation we find between H-alpha luminosity and 1.4 GHz radio continuum at z=0.24 is consistent with that observed at z=0 (Sullivan et al., 2001), suggesting that the mode of star-formation has not changed in the past 3 Gyr. Although we cannot measure HI emission for individual galaxies at z=0.24, we can measure the average neutral gas content of the sample by coadding the HI signal within the GMRT datacube using the positions and redshifts for 121 galaxies. The measured average HI mass is (2.26 +/- 0.90) x 109 Msol, or about 0.35M*. This leads to an estimate of the neutral gas density in the universe of Omega_gas = (0.00091 +/- 0.00042), which is consistent with measurements from damped Lyman-alpha at similar redshifts. The ratio of HI mass to star formation rate for this sample is entirely consistent with the z=0 relation found by Doyle & Drinkwater (2006). This means that the increased star-formation rate at z=0.24 is matched by a corresponding increase in the amount of neutral gas. We have recently extended this approach to the cluster Abell 370 at z=0.37, and our preliminary analysis indicates significant HI in the cluster galaxies, primarily concentrated in the bluer galaxies.
12.2 GHz Methanol Maser Survey
Benjamin Lewis and Simon Ellingsen
I am using the Mt Pleasant radio telescope radio telescope to
search for 12.2 GHz Maser emission toward known 6.6 GHz maser sources.
The 6.6 GHz sources represent a statistically complete sample drawn
from the Parkes/Jodrell methanol multibeam survey. This forms part of
a large international collaboration, whose aim is to achieve a
complete census of all the young high-mass star formation regions in
the Milky Way. I present preliminary results and comparisons between
the occurrence and relative intensity of the 6.6 and 12.2 GHz
transitions and mid-infrared colours in order to trace the phase (or
phases) of stellar evolution at which the different transitions occur.
Australian SKA Pathfinder
Diana Londish
Latest updates on the Australian SKA Pathfinder instrument
Head-Tail Galaxies as Barometers of Cluster Weather
Minnie Mao, Melanie Johnston-Hollitt, Jamie Stevens and Anne-Marie Brick
Using radio data at 1.4GHz from the ATCA we have identified ten Head-Tail (HT) galaxies (eight of which have never been published) in the central region of the Horologium-Reticulum (HR) supercluster. Parameters such as flux, spectral index and direction of travel have been determined for the HT galaxies.
The substructure of the central region of the HR supercluster has
been studied previously by Rose et al. (2002) however they only had
data for 532 objects whereas we have amassed a catalogue of well over
2000 spectroscopic redshifts for the region around A3125/A3128. This
is the largest spectroscopic catalogue for a Southern supercluster
and is the ideal dataset to probe the relationship between
environment and radio properties. We present the first results of
this study to investigate if HT galaxies can be used as barometers of
cluster weather.
A search for OH 6 GHz maser emission towards southern supernova remnants
Korinne E. McDonnell, Alan Vaughan and Mark Wardle
We present preliminary results of a survey using the Parkes
Methanol Multibeam receiver for 6049 MHz and 6035/6030 MHz OH masers
towards 36 supernova remnants and 4 fields in the Large and Small
Magellanic Clouds.
WFMOS-A: 2dF meets Echidna
Andrew McGrath, Sam Barden, Chris Blake and Ken Freeman
We have shown that some of the science goals of the proposed WFMOS
Gemini/Subaru facility are within the grasp of a four metre telescope.
A concept is presented for an Echidna fibre positioner with
approximately 1600 fibres to take advantage of the Anglo-Australian
Telescope's 2-degree field corrector, feeding spectrographs matching
the WFMOS Dark Energy and Galactic Archaeology survey
requirements.
Phase Dispersion Minimisation as a Period Determination Technique in Extra-Solar Planetary Transit Searches
Veronica Miller
Conventional grid searches of large datasets for planetary transit
signals are computationally expensive. We show that the phase
dispersion minimisation algorithm can be used to successfully recover
transit signals. We discuss our implementation of the method and
tests of the recovery rate for artificial signals.
MASH-II Planetary Nebulae from the AAO/UKST H-alpha Survey
Brent Miszalski, Quentin A. Parker, Agnes Acker and Anna Kovacevic
We present preliminary results from a new trawl through the
SuperCOSMOS on-line AAO/UKST H-alpha survey data of the Southern
Galactic Plane to uncover previously missed planetary nebulae (PNe)
using more sophisticated search techniques that can be applied to the
digital survey images. Dubbed MASH-II (Macquarie/AAO/Strasbourg
H-alpha Planetary Nebulae project second catalogue) it builds on the
significant discoveries of more than 900 Galactic PNe uncovered by
MASH to furnish an additional 250 spectroscopically confirmed PNe and
another 50-100 less probable candidates awaiting spectra. These
latest discoveries comprise two distinct groups: compact, barely
resolved PNe at one end and large, extremely low surface brightness
PNe at the other, significantly improving the fractions of such
Galactic PNe known and having implications for the extreme ends of
the PNe luminosity function and their interaction with the
ISM.
Low Surface Brightness Galaxies in Virgo: A Catalogue
Lesa Moore and Quentin A. Parker
Based on an ultra-deep image stacked from a unique set of 63
separate high-quality UKST R-band Tech-Pan films centred in the direction of
the Virgo cluster, we will catalogue hundreds of previously undiscovered low
surface brightness galaxies. A radial profile of each galaxy will be used to
determine parameters including size, scale length, central surface
brightness, position angle and ellipticity. All source data and resulting
measurements will be preserved in a VO-compliant catalogue that will
eventually be made available online.
Bringing Deep Space into the Classroom
Lesa Moore, Quentin A. Parker, Milorad Stupar, Lisa Germany
This DEST-funded project involves ten Australian high schools in
NSW and Victoria. In each of two observing rounds in 2007,
schools submit applications for observing time on the Faulkes
Telescopes (owned and operated by the Las Cumbres Observatory
Global Telescope Network). Applications are reviewed and ranked,
mirroring the process that professional astronomers go through
when applying for telescope time. Assessments are made based on
scientific and educational merit, as well as technical detail.
Observations are made by Faulkes Telescope staff in the UK, as
opportunities to use the Faulkes Telescope Real-Time Interface
are very limited in Australian time zones. Schools retrieve the
observational data and students perform their analyses in the
classroom. In each school numerous classes are involved, under
the guidance of one or two teachers. Project funding also
supports a Teacher Associate in each state whose role is to
visit the schools and offer support and astronomical expertise.
MOPS: the ultra-wide bandwidth millimetre-wave spectrometer for Mopra
Eric Muller, W. Warwick, D. Ferris, N. Lo, A. Walsh, M. Burton, J. Storey, A. Green, P. Edwards, and M. Hunt
Mopra, the largest single-dish millimetre wave telescope in the Southern Hemisphere has recently seen a number of important upgrades. The latest such upgrade, the Mopra Spectrometer (MOPS), is an 8 GHz wide signal-processor comprised of a 16-layer printed curcuit board, and 17 field-programmable gate arrays. This new "back end" provides two observing modes; access to either a contiguous 8 GHz block of spectrum, or up to 16 simultaneous 138 MHz-wide sub-windows.
MOPS allows the observer to take full advantage of the new
tuner-less receiver system, which replaced the earlier
narrow-band SIS system in 2006. The ability to observe
many spectral lines simultaneously is a powerful tool for
star formation studies. In addition, the very wide
bandwidth allows studies of wide, extragalactic emission
lines, multi-line surveys, or searches for species in
systems of poorly known redshift.
Mapping the Halo's RR Lyrae distribution
Simon Murphy
Because they are evolved objects and standard candles with large luminosities, RR Lyrae variable stars are ideal tracers of structure in our Galaxy's halo. We have recently undertaken a large-scale survey for RR Lyraes from 2000 deg2 of 2 and 3-epoch photometry along the entire ecliptic plane. Our survey is unique in that it covers many Galactic lines-of-sight, and offers excellent coverage of the southern halo, which has been previously under-sampled.
To efficiently select RRLs from a limited number of observations and colour information we have developed a unique, probabilistic selection method based on well-known RRL variability and colour distributions. Follow-up photometry and spectroscopy confirms a low level of contamination (~25%) from other blue variables and spurious detections.
From our sample of ~1500 candidates we have analysed the stellar
number density profile for both spherical and ellipsoidal models of
the halo. We also investigated the 3D spatial distribution of
candidates, from which several interesting overdensities of stars
have been found, some of which have not previously been identified.
Follow-up observations are ongoing to identify and confirm members of
these possible clumps or streams.
The new Molonglo Galactic Plane Survey (MGPS-2)
Tara Murphy and Anne Green
We present the first data release from the Molonglo Galactic Plane
Survey 2 (MGPS-2). MGPS-2 was carried out with the Molonglo
Observatory Synthesis Telescope at a frequency of 843 MHz and a
resolution of 45''x45'' cosec|δ|, making it the highest
resolution large scale survey of the southern Galactic plane. It
covers the range |b| < 10° and 245° < l
< 365° and is the Galactic counterpart to the Sydney
University Molonglo Sky Survey (SUMSS) which covers the whole
southern sky to δ < -30° (|b| >
10°).
The Great Melbourne Telescope and observational astronomy
Wayne Orchiston, Graeme L. White, Andrew Walsh and Jenny Andropoulos
When it became operational in 1869, the 48-in Great Melbourne
Telescope (GMT) was the largest equatorially-mounted reflector in the
world, and great advances in observational astronomy were expected.
Unfortunately, a number of factors conspired against this, and today
the GMT is commonly described as a "white elephant". In this paper
we examine the GMT, discuss the observations that were made with it,
and explain why most of these were never published.
Dynamics of a partially ionized medium
BP Pandey
We derive a general set of equations applicable to both weakly as well as fully ionized plasmas and disucss the relative importance of the ambipolar and Hall term in a weakly ionized medium. We show that both ambipolar and Hall diffusion depends upon the fractional ionization level of the medium.
The wave properties of a partially ionized medium is discussed in both ambipolar and Hall limits.
We show that wave damping in the ambipolar regime is dependent on
the fractional ionization. In the Hall regime, the wave is dependent
on both the ion-magnetization level as well as fractional ionization
of the medium. The results are discussed in the context of PPDs,
solar photosphere and Earth's ionosphere.
Spectral diagnostics and radial velocities using newly discovered Planetary Nebulae in the Large Magellanic Cloud
Warren Reid and Quentin A. Parker
We report the discovery of 461 planetary nebulae (PNe) in the central 252 region of the Large Magellanic Cloud (LMC). Candidate emission sources were discovered using deep, high resolution UKST stacked Short Red (SR) and Ha images which go deeper than any previously available. The two digitized stacks were then merged to reveal emission sources. Confirmatory spectroscopy was performed using 2dF on the AAT, the 1.9-m telescope at SAAO, the 2.3-m Advanced Technology Telescope at the MSSSO, FLAMES on the ESO VLT2 and 6dF on the UKST. All the previously known PNe in the survey area have also been spectroscopically observed, resulting in a sample of 629 PNe.
These have now been used to produce nebula diagnostics including temperatures, electron densities and masses. Together with newly derived excitation classes, these diagnostics and fluxes have led to the discovery of new evolutionary tracks for LMC PNe. Different excitation levels are shown graphically where luminosity gradients are compared to masses and densities. Newly derived dynamical ages are also presented. PN abundances have been determined, comprising the largest sample ever obtained in any galaxy beyond the Milky Way, allowing clear trends to be graphically displayed for the first time. A new luminosity function has been constructed, finally revealing the shape of the faint end. Radial velocities from the complete LMC sample have been used to compare PN kinematics to that of the HI disk. The resulting transverse velocity and angle of inclination for PNe in the central 25 deg2 region of the LMC are presented.
Models of Interacting Dark Energy and Dark Matter
Darren J. Rowland
We consider cosmological models in which Dark Energy interacts
with Dark Matter. Best-fit parameter values are obtained using
current observations of Type 1a Supernovae.
The Nuclear Ring in the Barred Spiral Galaxy IC 4933
Stuart D. Ryder, Rob Sharp and Sam Illingworth
We present IRIS2 infrared images of a circumnuclear star-forming
ring in the centre of IC 4933, together with follow-up spectroscopy
with the GNIRS Integral Field Unit. Maps of the Pa-beta and CO line
strengths allow us to reconstruct the star formation history of the
ring.
Bok Globules and Isolated Star Formation
Martin Saul
Nearby Bok globules are the best places for detailed study of the
initial properties and conditions of individual star-forming cores,
their kinematic structure, chemical evolution, and the physics of
fragmentation and collapse.
Correlation between Optical and Radio Luminosity function of Radio Loud Quasars
Swati Singh
QSOs have played an important role as cosmic probes of the young Universe: they are used as light beacons for absorption-line and gravitational lensing studies, as markers of galaxy formation activity and have guided in hunting for primeval galaxies. The purpose of this poster is to discuss the relation between the optically-selected and the radio-selected quasars and to derive the optical luminosity function (OLF) for radio-loud quasars to study evolutionary effects. The shape and evolution of the luminosity function provide important constraints on the nature of radio emission in the massive galaxies and its cosmic evolution. We calculated the OLF for a sample of Parkes Half Jansky Flat-Spectrum (PHFS) radio sources and compared our result with the OLF obtained from the 2dF Quasar Redshift Survey (Boyle et al. 2000; Croom et al. 2001), based on ~11,000 sources.
To test how the population of QSOs evolves with redshift and whether these radio selected quasars evolve in same fashion as the optically-selected ones, we divided the LF into 3 redshift bins, z < 0.3, 0.3 < z < 1.2 and z > 1.2. We found that the shape of the OLF as seen from the middle and higher redshift bin is quite flat which indicates that the space density of radio-loud quasars lying between -28 < MB < -24 is constant. This behaviour is different from optically-selected quasars that demonstrated steep drop in space density at high luminosities. No conclusion can be drawn from the low redshift bin due to small number of quasars, however the OLF looks to be consistent with the Boyle et al. 2000 OLF.
We also performed Monte Carlo simulations to study the luminosity
correlation between the optical and radio bands for radio selected
radio loud quasars. We reproduced similar shape of OLF from Monte
Carlo simulation as shown by Boyle et al. 2000, for randomly
generated absolute magnitude and radio fluxes (≥ 0.5 Jy) for zero
variance. As we go on increasing variance the slope becomes flatter
and flatter for increasing values of variance and does not drops off
rapidly as observed by Boyle et al. 2000. No correlation was found
between radio and optical luminosity functions of radio selected RLQs
in PHFS sub-sample for increasing values of variances, and it cannot
be described by Pure Luminosity Evolution, although we require large
number of higher redshift quasars to confirm these
results.
An Examination of Selective Imaging Techniques
Andrew Smith
We have tested the method of selective imaging, or "lucky imaging", in light of the original theories of Fried (1966,1978), with the aim of optimising the technique and broadening its application. Selective imaging involves taking many successive short exposure images of a sufficiently bright source, every frame is analysed for sharpness and only those that meet given quality criteria are selected to combine into a final image. This makes use of the random moments of clarity that occur during imaging, and substantially reduces the distorting and blurring effects of seeing as well as dark current.
Imaging was undertaken on both the AAT and the 1m ANU telescope with
various aperture masks, frame exposure times, and colour filters. Results
from observations of bright stars using a simple ~Sbrightest pixel~T
criterion are presented. These images show improvements in Strehl ratios
with increasing selectivity. In agreement with theory, more usable frames
are found when using smaller apertures, and greater improvements in Strehl
are obtained at higher wavelengths. The issue of the longest useful frame
exposure time is presented. Initial results of planetary images using
Fourier analyses are also shown.
The Circumnuclear Disk at the Galactic Centre
Ian Smith and Mark Wardle
The Circumnuclear Disk (CND) is a cloud of dust and gas rotating about the radio source Saggitarius A*, a black hole with a mass of 4 million suns at the centre of the Milky Way galaxy. Around SagA* is a central cluster of young stars and streamers of ionised gas and dust known as the mini spiral, all within 1.6 parsecs (pc), the inner radius of the CND. The outer radius of the disk is some 6pc and its thickness varies from about 0.2pc at the inner radius to 2pc at the outer edge.
The aim of the study is to interpret observations of different molecular species using an excitation programme, written by Mark Wardle, to understand and measure the underlying physical conditions in the ring. A model of the ring's structure will be developed and tested for consistency with current propositions. The study has commenced by using HCN observations from Christopher and Scoville ApJ 622 346-365 March 2005.
New Supernova Remnants in the Southern Galactic Plane
Milorad Stupar and Quentin A. Parker
Search for the new filamentary emission and nebulosities that could be possible new Galactic SNRs were undertaken using images of the AAO/UKST HAlpha survey of the Southern Galactic Plane. For 21 out of 60 classified nebulosities, spectral observations, maintained at the spectrographs of 1.9m telescope of South African Astronomical Observatory and 2.3m telescopes of Mount Stromlo and Siding Spring Observatory, confirmed presence of classical optical SNR emission lines such are OII at 3727Å, OIII at 4959 and 5007Å, OI at 6300 and 6364Å, NII at 6548 and 6584Å and especially presence of SII doublet at 6717 and 6731Å. The line ratio diagnostic criteria of Fesen and Blair (1985) for SII/HAlpha > 0.5 was used to confirm the emission from shock excited gas characterized for supernova remnants and to separate them from HII regions and planetary nebulae. This ratio in sample of 21 optical candidate SNRs was between 0.6 and 3.8.
All 21 nebulosities and filamentary structures were checked in the available radio surveys against possible connection with radio sources at four different frequencies/surveys: SUMSS at 843 MHz, NVSS at 1.4 GHz, Parkes at 2.4 GHz and PMN at 4.85 GHz. In 11 cases, if not complete then partial match between optical and radio structures was found or HAlpha filamentary structures registered inside the presumed radio borders. Additionally, X-ray sources are detected inside optical/radio borders or in the vicinity of 11 observed SNR candidates. Three candidates from the sample may have an associated pulsar.
Support toward SNR classification also comes from the morphological
structure of observed object, where 11 new candidates are in the form
of a shell or arc and 9 in the classical form of HAlpha filaments,
typical for optical SNRs. All mentioned facts confirm that the new
Galactic supernova remnants were identified (18 out of 21) and that
optical spectra verify that G288.7-6.3, G315.1+2.7 and G332.5-5.6,
previously registered as SNR candidates from the radio observations,
are new Galactic remnants.
Planetariums in Astronomy Education (Action) Research
Ian Tasker
What impact could a planetarium in Sydney have on astronomy and space science education's profile?
Collisional excitation of OH(6049 MHz) masers in supernova remnant - molecular cloud interactions
Mark Wardle
OH (1720 MHz) masers serve as indicators of SNR - molecular cloud
interaction sites (Frail et al. 1994; Wardle & Yusef-Zadeh 2003).
These masers are collisionally excited in warm (50-100 K) shocked gas
with densities of order 105 cm-3 when the OH
column density is in the range 1016—1017
cm-2. Here I present excitation calculations which show
that when the OH column density exceeds 1017
cm-2 at similar densities and temperatures, the inversion
of the 1720 MHz line switches off and instead the 6049 MHz transition
in the first excited rotational state of OH becomes inverted. This
line may serve as a complementary signal of warm, shocked gas when
the OH column density is large.
Collective Vortex-Line Motion in Pulsar Glitches
Lila Warszawski
The role played by superfluid vortices in spin-frequency glitches
in neutron stars continues to receive much attention. The
hypothesis that these glitches are caused by collective unpinning of
105-1012 vortices is, in general, studied under the continuum
(hydrodynamic) approximation using the HVBK equations. We propose
that the knock-on behaviour of individual vortex lines, and their
mutual interactions, may play an important role in precipitating
glitches. As a preliminary attempt to study the collective behaviour
of superfluid vortices inside a rotating fluid, we solve the coupled
Navier-Stokes (for the viscous fluid) and Schwarz (for the motion of
the vortex line) equations in an effort to model the interplay of the
superfluid vortex and the viscous fluid. We find that the Ekman
spin-up time is modified according to the strength of the mutual
friction betweeen the viscous and inviscid fluids. We subsequently
investigate the gravitational signal arising from the viscous fluid
flow.
The contribution of the Potts Hill Field Station to international radio astronomy
Harry Wendt, Wayne Orchiston and Andrew Walsh
During the 1950s Australia was one of the world's foremost astronomical nations owing primarily to the dynamic Radio Astronomy Group within the Commonwealth Scientific and Industrial Organisation's Division of Radiophysics. Most of the observations were made at the network of field stations maintained by the Division in or near Sydney, and one of the most prominent of these was located at Potts Hill, the site of Sydney's major water-distribution reservoirs.
This poster paper reports on a doctoral research project, and outlines the amazing range of radio telescopes developed at this field station; the types of solar, Galactic and extragalactic research programs to which they were committed; and the pioneering young men and women who played a key role in the early development of radio astronomy.
NOIRCAT — The Northern HIPASS Optical/InfraRed CATalogue
O. Ivy Wong
We present the Northern HIPASS Optical/InfraRed CATalogue (NOIRCAT), an optical/near-infrared counterpart catalogue fro the Northern HIPASS catalogue (NHICAT).
We define a dark galaxy to be an isolated HI source which has no detectable stars (i.e. optically-dark).
Using the direct findings of NOIRCAT, the only dark galaxy candidates
(ie. HI detections without optical counterparts) are located in the
direction of the Galactic plane. The upper limits of our probability
calculation suggests that we can rule out the likelihood of NOIRCAT
containing more than 1 dark galaxy at a 95% confidence level.
Varying systemic velocity detected in the eclipsing binary delta Scuti star, RS Cha
Robyn M Woollands
RS Cha is a double-lined spectroscopic eclipsing binary (SB2e) which has both its components identified as being δ Scuti stars. 320 spectra were obtained at Mt John University Observatory (MJUO) using the 1.0 m McLellan telescope and the High Efficiency and Resolution Canterbury University Large Echelle Spectrograph (HERCULES). Cross-correlation methods were used to generate radial velocities and to solve for the orbital solution. A variation in the systemic velocity of about 600ms-1 is apparent in the time span of our dataset. This prompted further investigation, that has enabled us to include all the historic published systemic velocity values into our analysis. In this poster we present arguments for the existence of a third component in the RS Cha system.
In addition, we determined the stellar masses of both components
based on our orbital elements. These were 1.842±0.032 and
1.829±0.031 solar masses for the primary and secondary
components respectively. Using Fourier transform inversion techniques
we calculated the stellar rotational velocities for the primary and
secondary components to be 68±2 kms-1 and
72±2 kms-1 respectively, and thus we can confirm
the claim made by Alecian et al. (2005) that the RS Cha system is synchronized.
Correlations in the timing data of pulsars in the Parkes Pulsar Timing Array
Daniel R.B. Yardley
The use of a pulsar timing array such as the Parkes Pulsar Timing
Array (PPTA), allows for the investigation of several terrestrial and
astrophysical phenomena through the analysis of correlation in the
pulsar timing data sets. An error in Terrestrial Time should leave a
signature that is identical for all pulsars, and hence will give a
correlation coefficient of unity. An error in the solar system
ephemerides should leave a dipole correlation signature across the
sky, whilst a gravitational wave leaves a quadrupole signature across
the sky. The preliminary steps of these investigations and the
statistical methods involved are discussed.
| Program | All Days |
Sunday |
Monday |
Tuesday |
Wednesday |
Thursday |
Posters |
| Abstracts | Posters A-K |
Posters L-Z |
Monday |
Tuesday |
Wednesday |
Thursday |
Lunch Meetings |
For further information (and additions or corrections), contact: qap@physics.mq.edu.au