ASA 2007

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 - Tuesday

Session Five - Galaxies: Evolution and Local Galaxies

09:00-10:30

Spectroscopic dissection of E+A galaxies

Michael Pracy

The characteristic E+A galaxy spectrum - strong Balmer-line absorption superimposed upon an elliptical galaxy type spectrum with no emission lines - is a signpost to galaxies in the process of evolution. These galaxies are in the midst of a rapid transition from a star-forming to a quiescent state. The key to further progress in this field is the identification of the formation mechanisms of these galaxies as a function of environment. The only way to differentiate between the various proposed formation mechanisms is to understand the spatial distribution of the star-formation histories and the internal kinematics of the young and old stellar populations. To this end, we are undertaking a comprehensive imaging and spectroscopic campaign of a robust sample of E+As we have selected from the 2dF Galaxy Redshift Survey. We have used the Integral Field Unit capability of the Gemini/GMOS and the VLT/VIMOS systems, as well as long-slit mapping with the ANU 2.3-m to obtain spatially-resolved stellar population and kinematic information of this sample. We will present the results of these studies.

Galloping Galaxies!

Kevin Pimbblet

Galloping (brightest cluster member) galaxies offer us the chance to probe the formation and evolution of massive giant ellipticals in a novel manner. This talk will review our recent work in finding a cD galaxy with the largest peculiar velocity to date and will present work in progress from Gemini South GMOS observations of a large sample of galloping galaxies. We are using these observations to differentiate between hierarchical assembly versus cannibalistic processes.

Massive galaxies at z=2-3.5 - evolution and environment

Julia Bryant

The hierarchical model of early galaxy formation predicts that galaxies formed through mergers of smaller clumps of material to eventually form the most massive galaxies. However, the discovery of very massive 10¹² solar mass galaxies at redshifts greater than 2 calls into question how such a large mass could be assembled within 1-2 Gyr after the big bang. Feedback mechanisms have been introduced into galaxy modeling to try and explain the rapid formation of massive galaxies, but such mechanisms have remained largely untested with observations. Our project has been searching for high redshift radio galaxies in order to constrain the early evolution of the most massive galaxies and has successfully identified a sample of z = 2-3.5 massive galaxies which coincide with the time at which star formation rate density of the universe was at its peak.

Galaxy Accretion and Feedback @ Red-shift Zero (GAF@RZ)

Robert Braun

Multiple independent lines of evidence demonstrate that the surface area subtended by atomic hydr ogen at column densities near 10¹⁷ cm^-2 exceeds that seen at 10¹⁹ cm^-2 by about a factor of 30. Intervening column densities are rarely encountered because of ionization in the intergalactic radiation field. Although at the limits of current technology to detect, deep integrations with the Parkes Multi-Beam system can reach the required sensitivity to image such gas in the local universe. This HI 'Cosmic Web' is likely to be in the form of filaments and other diffuse structures in the vicinity of massive galaxies, although only a single confirmed example has been imaged to date. In view of the long dynamical timescales, these features retain essentially a Hubble-time's worth of interaction and feed-back history. We are proposing to carry out the first systematic study of these features; confirming the most significant detections from our ongoing wide-field survey and explicitly targeting the extended (~1 Mpc) environment of the most massive galaxies within 20 Mpc.

FIGGS: Faint Irregular Galaxies GMRT Survey

Ayesha Begum

We will present results from the Faint Irregular Galaxies GMRT Survey (FIGGS), an observing program to observe a large (~ 65) number of faint (M_B< -15.0), nearby, dwarf irregular galaxies in HI, at high velocity resolution (1.6 km/s) with the Giant Metrewave Radio Telescope (GMRT). The GMRT HI images obtained at a variety of spatial resolutions viz 40", 20" and 10" are supplemented by V and I band HST images, as well as the H-alpha images from the 6-m BTA telescope. In addition distances accurate to ~10% are available from several of the galaxies in our sample. Our study is, by far, the most detailed multi-wavelength study of such faint galaxies. The FIGGS survey has uncovered galaxies like NGC 3741 and AndIV which have very extended HI disks and thus provide an unique opportunity to trace the extended distribution of dark matter around faint galaxies. We will report on studies examining the correlations between dark and luminous matter (e.g. the Baryonic Tully Fisher relation), and star formation and the gas distribution and kinematics in the FIGGS sample.

Deepest Near-IR Surface Photometry of Galaxies in the Local Sphere of Influence

Emma Kirby

We present near-IR, H-band, deep (SB_lim = 26 H arcsec^-2 or 4 mag deeper than 2MASS) imaging of 65 Local Volume galaxies from the 4m Anglo-Australian Telescope. Global parameters such as total magnitudes and stellar masses have been derived and the new NIR data combined with HI 21cm data (from the Local Volume HI Survey at the Australia Telescope Compact Array) 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.

Session Six - The Magellanic Clouds and the Local Group

11:00-12:30

The Magellanic Stream: a mystery resolved

Joss Hawthorn

Since its discovery over a decade ago, the source of ionization along the Magellanic Stream has defied explanation. We now provide a simple but elegant explanation — consistent with all known observational constraints — that in turn has important consequences for the lifetime and eventual fate of the Stream.

Zooming into the ISM of the SMC

Erik Muller

We present the highest-available resolution observations of the neutral hydrogen ISM in the most active and turbulent part of the nearby Small Magellanic Cloud. These ATCA observations of the South-West SMC are combined with existing datasets to extend the previous resolution limits down to ~2 pc. In doing so, we have contiguously sampled scales from ~kpc down to the parsec level. At these smaller scales, we are now probing the scales over which star formation is expected to directly shape and modify the ISM by the action of stellar winds, planetary nebulae, and SNe.

Spectral diagnostics and abundances based on a new population of planetary nebulae discovered in the LMC

Warren Reid

We report our discovery of 460 planetary nebulae (PNe) in the central 25deg² region of the Large Magellanic Cloud (LMC). Candidate emission sources were discovered using deep, high resolution UKST stacked Short Red (SR) and Hα 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. Optical spectroscopy not only allowed us to identify PNe from our large sample but results are allowing physical conditions to be determined. The new PNe have implications for LMC PN luminosity function, kinematics, abundance gradients, chemical evolution and the initial to final mass relation for low to intermediate mass stars.

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, revealing the shape of the faint end. This is compared to a new luminosity function constructed from a very complete sample of local PNe. Radial velocities from the complete LMC sample have been used to compare PN kinematics to that of the HI disk.

An Optical and Radio Polarization Study of the Magnetic Field in the Small Magellanic Cloud

Sui Ann Mao

We present a study of Faraday rotation measures towards extragalactic radio sources behind the Small Magellanic Cloud (SMC) to determine the magnetic field properties of the galaxy. Consistent negative rotation measures (RMs) across the galaxy suggests that the line-of-sight magnetic field is coherently directed away from us with a strength ?0.3± 0.1?G. Optical starlight polarization of stars in the SMC allows one to compute the plane-of-the-sky magnetic field strength using the Chandrasekhar-Fermi (C-F) Method. An ordered magnetic field strength of 3.2±0.7 ?G in the plane of the sky is obtained from the analysis. The fluctuation in RMs implies a random field strength of 3 ?G, which is consistent with the estimation from combining results of the C-F method and the measured synchrotron intensity of the SMC. We construct a three-dimensional magnetic field model of the SMC assuming that starlight polarization and RMs probe the same fields in the SMC. The vector defining the direction of the coherent SMC field is largely confined to the plane of the sky, but has a 180 degree ambiguity in its direction. For one of the two possible directions, there is a reasonable degree of alignment between the SMC field and the line joining the SMC to the LMC. Such an alignment would suggest that the observed SMC magnetic field might be part of a larger magnetic loop associated with the entire Magellanic system. We consider possible field generation mechanisms such as dynamo mechanisms, tidal interactions, and ram pressure effects, to explain the observed magnetic field in the SMC.

The Stromlo Missing Satellites Survey

Shane Walsh

ANU is currently constructing the Skymapper telescope which will undertake a photometric survey of the entire southern sky in the spirit of SDSS. We will be searching this catalog for previously undiscovered Milky Way Satellite galaxies using an algorithm that has already yielded one such new object in the Sloan Digital Sky Survey Data Release 5, dubbed Bootes II. I will highlight our method and prospects for this exciting new survey.

The Monoceros Ring and Canis Major Stream: Warp and Flare or Dwarf Remnant?

Richard Lane

I will present the results of a recent wide field camera survey of the outskirts of the MW, over the Galactic longitudes l=(193 - 276) deg, revealing new substructure, including several new detections of the Monoceros Ring and evidence for a new tidal feature of the Canis Major overdensity, the Canis Major stream, and show that these data are inconsistent with the idea that the substructure can be explained with a warped and flared Galactic disc. Data such as these are leading toward a coherent theory of the evolution of spiral galaxies, one of the great outstanding problems of astrophysics.

Session Seven - Galactic Science

13:45-15:30

Mopra and Galactic Star Formation: at the Spectral Forefront

Peter Barnes

The Mopra antenna's new spectroscopic capabilities put it at the forefront of research into star formation in molecular clouds. Here I describe 2 major survey projects that are taking advantage of this technology: CHaMP and C2D.

With CHaMP (the Census of High- and Medium-mass Protostars) we are surveying, in a systematic and unbiased way, all evolutionary stages of higher-mass star formation in a large sample of massive Giant Molecular Cloud cores. From our first of four observing seasons, we have already identified a few interesting statistical trends and made some unexpected discoveries, based on the rich spectroscopic mapping data that Mopra gives us.

As part of the Spitzer Legacy Project C2D (From Cores to Disks), we have also used Mopra to image (simulataneously in several spectral lines) all 40 dense molecular cores in the southern hemisphere C2D sample. We report on some preliminary results for this project as well.

A search for OH 6 GHz maser emission towards southern supernova remnants

Korinne McDonnell

OH masers at 1720 MHz have proven to be excellent indicators of interactions between supernova remnants and molecular clouds. Recent calculations suggest that the 6049 MHz OH maser line is excited for higher column densities than for the 1720 MHz line. It is therefore a potentially valuable indicator of remnant-cloud interaction.

ChIcAGO: Chasing the Identification of ASCA Galactic Objects

Gemma Anderson

The ChIcAGO (Chasing the Identification of ASCA Galactic Objects) survey is designed to identify the unknown X-ray sources discovered during the Advanced Satellite for Cosmology and Astrophysics (ASCA) Galactic Plane Survey. ASCA studied the inner region of the Galactic plane, -45° ≤ \ell ≤ 63° and |b| ≤ 0.\!\!^\circ4$, in the energy band 0.7-10 keV with a spatial resolution of ~3'. The poor spatial resolution resulted in very few of the 163 sources being identified. Little is known about the remaining objects, especially those that primarily emit in the range 2-10 keV. In ChIcAGO, we plan to identify all these unidentified ASCA sources by obtaining sub-arcsecond localisation from Chandra, combined with multi-wavelength follow-up derived from recent surveys, archival data and new observations. When completed, ChIcAGO will provide a new understanding of the distributions, birth-rates and evolution of Galactic X-ray sources, with a particular focus on the progenitors and products of core-collapse.

The Mopra G333 Survey

Maria Cunningham

The Mopra telescope has been used to map a 1.2 x 0.6 degree region of the southern Galactic plane in the rotational transitions of 20 different molecules. The survey, made possible by the wide bandwidth and high spectral resolution capabilities of the the new MOPS receiver, has produced a unique dataset that is being used to give new insights into the dynamics and chemistry of the interstellar medium. Here we present some highlights of the results, showing how the combination of molecules can be used to trace dynamical structures such as molecular shells, outflows, and gas filaments, and how these are related to the star formation activity within the region. For example, the molecule N₂H⁺ seems to be a surprisingly good tracer of shell structures within the G333 cloud, of which there are some half-dozen. This molecule is generally found to trace cool, dense quiescent gas, and in this case seems to be tracing gas compressed by the shock front of an expanding shell. In some places the shells have begun to fragment and form dense cores, leading us to conclude that within the G333 region, a significant portion of the star formation is being triggered by dynamical feedback.

Serendipity and the 2XMM catalogue

Sean Farrell

ESAs XMM-Newton X-ray space observatory has been in operation for almost 7 years, observing thousands of sources with some of the most powerful telescope mirrors and most sensitive cameras ever developed. The combination of a large field of view and relatively high spatial resolution has resulted in a vast number of serendipitous source discoveries. The 2XMM Serendipitous Source Catalogue is currently being compiled, providing a wealth of data on previously unknown faint X-ray sources and their optical counterparts. In this talk I will introduce the XMM-Newton mission and describe some of the serendipitous detections that have come to light recently including flares from active stars, cataclysmic variable orbital periods, and thermonuclear flashes from neutron star X-ray binaries.

Kinematics of HI in the inner Milky Way

Naomi McClure-Griffiths

We present a study of the kinematics of atomic hydrogen (HI) in the inner Milky Way, including a new derivation of the rotation curve of the inner Galaxy. This is the most densely sampled rotation curve ever produced for a galaxy. We have used the Southern Galactic Plane Survey HI dataset to place new limits on the streaming motions associated with spiral arms in the inner Milky Way. This talk will focus on the inner Galaxy rotation curve and what HI kinematics can tell us about random motions in the interstellar medium.

Careless Whispers from High-Velocity Clouds: A Look at Ionised Gas in the Galactic Halo with WHAM

Greg Madsen

Recent surveys of interstellar hydrogen have revealed hundreds of neutral gas clouds that are moving anomalously with respect to Galactic rotation. These high-velocity clouds (HVCs) have radial velocities of hundreds of kilometers per second and span a wide range of sizes and morphologies.

The origin of the clouds remain widely debated due to poor distance and metallicity constraints. Several HVCs have been now been detected in ionised gas, offering new clues to their nature. Here we report on new data from the Wisconsin H-Alpha Mapper (WHAM) toward Complex A, a large filamentary HVC that extends up to 40 degrees above the Galactic plane. It is one of only two HVCs of known distance, residing 4-8kpc from the Sun and offering a unique probe of physical conditions in the low density Galactic halo. We use the strength of the H-alpha emission to place the strongest observational constraints on the escape of ionising radiation from the Galaxy. We combine our data with absorption line measurements of other ions to infer how HVCs are ionised as they plow through the halo.

Session Eight - Galactic Science and Surveys

16:00-18:00

High Resolution Spectral Models for Globular Clusters

Michael Albrow

The internal velocity dispersions of globular clusters are typically < 20 km/s, so that there is no fundamental barrier to spectral observations at resolutions R > 20,000. The current generation of 8-10m class telescopes and the next generation of extremely large telescopes will allow spectroscopy of extragalactic globular systems that approach this limit. To aid in the analysis of such observations we are developing high-resolution simple stellar population models. I will describe the models and their first application to Local Group clusters at moderate resolution. Direct fitting of spectra is employed using Markov Chain Monte Carlo to derive ages, metallicities and CN abundances.

MASH-II Planetary nebulae from the AAO/UKST H-alpha Survey

Quentin A. Parker

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.

Detection of silicon monoxide from a massive dense cold core

Nadia Lo

With the new Mopra Spectrometers (MOPS) we have carried out multi-molecular line survey of the giant molecular cloud, G333. From this multi-line survey we have detected thermal SiO emission (a shocks and outflows tracer) from the massive cold dense core G333.125-0.56. The core is invisible at wavelengths shorter than 70 um and has compact 1.2 mm dust continuum. From ammonia inversion lines we obtained a temperature of 13 K. In addition we have also detected a 22 GHz water maser in the core, together with methanol maser emission, suggesting the core will host massive star formation.

Three dimensional distributions of HI and H2 gases in the Galaxy

Hiroyuki Nakanishi

We derived three-dimensional maps of the interstellar medium (ISM) using the latest HI and ¹²CO(J=1—0) survey data, and rotation curves, based on the kinematic distance. Though there was a near-far ambiguity in deriving an inner Galaxy map, we divided the near and far components, by fitting a model of ISM vertical distribution to the observational data. HI and H₂ maps are advantageous to investigate structures of the outer and inner Galaxy, respectively. We combined HI and H₂ maps to obtain a total gas density map, which enabled us to trace spiral arms clearly in the entire Galaxy.

We could trace the Outer, the Perseus, the Sagittarius-Carina, the Scutum-Crux, and the Norma arms as logarithmic spiral arms with pitch angles of 11° — 15°. These maps are useful data to investigate characteristics of the ISM disk. As an example of interesting characteristics, we found that the scale-height of the HI disk is small at spiral arms and large at inter-arms.

HOPS: A Mopra survey of the southern Galactic plane

Andrew Walsh

With the advent of recent upgrades on the Mopra radiotelescope, it is now possible to quickly survey large areas of the sky at multiple frequencies simultaneously. I will outline a major project to survey 90 square degrees of the Galactic plane with Mopra. The survey will map emission from water masers and ammonia, as well as a number of other astrophysically important lines.

I will also present results of a pilot survey conducted last summer.

Cold, Cold Cores in the Delta Quadrant Survey (DQS)

Michael Burton

What initiates star formation within a cold dense core, and what happens in that core afterwards? In an effort to address such questions we have been studying mm-continuum-emitting dust cores within the G333 molecular cloud complex (a part of the DQS-survey being undertaken with Mopra). We have selected the very coldest cores based on their absence of mid-infrared emission. We have made use of far-IR fluxes at 150 and 210 microns, obtained through large apertures in a balloon-borne experiment (Karnik et al, 2001), together with Spitzer IR, SEST mm-continuum and Mopra mm-line images, to select those individual cores where the spectral energy distribution can be determined with reasonable confidence. For these, we have determined basic physical parameters for cores associated with the earliest stages of massive star formation (i.e. luminosities, core masses, temperatures and densities). We examine how a proxy for star formation efficiency (i.e. luminosity / mass) varies with these parameters. It appears to be approximately constant once the core temperature has warmed to be greater than ~50K.

The Southern Sky Survey: a New View of the Galactic Halo

Stefan Keller

In preparation for the Southern Sky Survey performed by the SkyMapper telescope, we have revisitied archive data from the Mt. Stromlo 50 inch telescope. Spanning 2000 square degrees, our survey for RR Lyrae variables has given us a detailed view of the Milky Way's halo. In it we see a series of significant condensations that may be understood to be disrupted accreted satellites. I will discuss our findings and look forward to the era of the Southern Sky Survey.

A blind search for Ultra-Compact HII regions at 20 GHz

Tara Murphy

We have carried out a blind search for compact sources with rising spectral indices in the southern Galactic Plane. This work uses two new radio surveys of the southern sky; the Australia Telescope 20 GHz survey (AT20G) and the Molonglo Galactic Plane Survey (MGPS-2) at 843 MHz. The AT20G survey was used to define an initial sample of bright sources with f > 200 mJy. MGPS-2 was used to measure a spectral index for each source and narrow the sample to sources with α²⁰_0.843 > 0.1. We have followed up these sources with the Australia Telescope Compact Array and now have H70α recombination line measurements and higher resolution images at 20 GHz. Combining this data with MIR images from Spitzer and MSX we have identified a list of candidate UCHII regions, several PNe and a small sample of extragalactic sources. Several of these bright compact sources are possible calibrators for the Planck mission.

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