Navigation News Annual Scientific Meeting Participants Program Posters Events Opening Reception ESO Agreement Signing Harley Wood Public Lecture ASA Conference Dinner Introduction To Machine Learning Prizes Bok Prize Charlene Heisler Prize Ellery Lectureship Harley Wood Lecture Louise Webster Prize Policies Sponsors Harley Wood Winter School
Now

# Astronomical Society of Australia's Annual Scientific Meeting – Program

Click on session headings to view the session; click on talk titles to view their abstracts.

If you'd like to download a copy of the program, you may do so from here (412.8 KB).

## Sun, 9 Jul

### Registration

University House

Registration will open at 4pm, and will remain open until the end of the Opening Reception.

### Opening Reception

Registration required

4:30 p.m. – 6:30 p.m. @ University House, ANU

This event is sponsored by the ANU Research School of Physics and Engineering.

The Opening Reception for the Annual Scientific Meeting will take place at ANU University House on Sunday, 9 July. Drinks and canapés will be provided.

The registration cost for this event is free for those attending the ...

## Mon, 10 Jul

### Welcome to Country

Molonglo Theatre

A Welcome to Country Ceremony will be conducted by Ngunnawal Elder Tyronne Bell.

### Welcome

Molonglo Theatre

A welcome address will be made by Professor Brian Schmidt AC, Vice-Chancellor of The Australian National University.

Molonglo Theatre

### T1, 9:30–9:45 a.m. — Murchison Widefield Array: Science and technology on the path to SKA Randall WAYTH, Curtin University

The Murchison Widefield Array (MWA) radio telescope is the technical and scientific precursor instrument to the Low Frequency component of the future Square Kilometre Array (SKA-Low). It was built by an international science collaboration from six countries and is located in the remote Murchison region of Western Australia. Scientifically, the MWA has generated results on the Earth's ionosphere, the heliosphere, nearby stars, our Galaxy, distant galaxies and AGN, and all the way back to the early universe. The MWA has been in full operations since mid 2013 and the expertise gained in designing and operating a low frequency radio telescope has had direct benefits to SKA-Low in the pre-construction phase. This talk will provide an overview of the status, science and technical progress of the MWA, including the SKA context.

### T2, 9:45–10:00 a.m. — Fireballs, the ionosphere, and space debris from the MWA Paul HANCOCK, Curtin University

The MWA has been engaged in a number of projects that focus on observing the very local universe. Events, objects, and propagation effects in the last nano-parsec can form an important foreground which must be considered by projects interested in the more distant universe. In this talk I'll describe the effects of the ionosphere, the incidence and influence of Fireballs, and our ability to detect space debris with the MWA.

### T3, 10:00–10:15 a.m. — A multi-frequency radio continuum study of the Magellanic Clouds Bi-Qing FOR, International Centre for Radio Astronomy Research/University of Western Australia

The GaLactic Extragalactic All-Sky MWA (GLEAM) survey is the main MWA continuum survey that covers the sky south of declination +30 degrees and at frequencies between 72 and 231 MHz. We utilize the data from the GLEAM survey to carry out a continuum study of the Magellanic Clouds. I will present the derived global spectral indices and radio spectral index maps. In conjunction with multiwavelength data, we investigate the star formation rate and discuss the implication of varying spectral index across the Magellanic Clouds in relation to star formation processes.

### T4, 10:15–10:30 a.m. — Engineering Development Array: A low frequency radio telescope utilising SKA precursor technology Marcin SOKOLOWSKI, Curtin University

We present the design and performance of the Engineering Development Array (EDA), which is a low frequency radio telescope comprising 256 dual-polarisation dipole antennas working as a phased-array. The EDA was conceived of, developed, and deployed in just 18 months via re-use of Square Kilometre Array (SKA) precursor technology and expertise, specifically from the Murchison Widefield Array (MWA) radio telescope. It demonstrates the practicality and feasibility of using MWA-style precursor technology for SKA-scale stations. Using drift scans and a model for the sky brightness temperature at low frequencies, we have derived the EDA's receiver temperature as a function of frequency and shown that the EDA is sky-noise dominated over most of the frequency range measured between 60 and 240 MHz. We used the EDA in interferometric mode with the MWA in order to derive absolute sensitivity of the array from calibrated visibilities. The measured array sensitivity matches very well with a model based on the array layout and measured receiver temperature.

### Morning Tea

Foyer, Crawford School of Public Policy

Molonglo Theatre

### T5, 11:00–11:15 a.m. — The First Data Release of SkyMapper's Southern Sky Survey Christopher ONKEN, The Australian National University

We present the first Data Release from the SkyMapper telescope's Southern Sky Survey. DR1 covers approximately 20,000 square degrees to a depth of ~18mag in the 6 standard SkyMapper filters (uvgriz), and includes photometry for roughly 300 million stars and galaxies. Proprietary access to the survey products is being provided to Australian astronomers through the All-Sky Virtual Observatory, and we will describe the tools available for catalogue queries, image cutouts, and cross-matching to other datasets.

### T6, 11:15–11:15 a.m. — The SkyMapper Search for Extremely Metal-Poor Stars in the Galactic Halo Gary DA COSTA, Australian National University

The filter system employed in the SkyMapper survey of the southern sky incorporates a narrow ‘v’ filter centered on the Ca II K-line at 3933Ang, facilitating the identification of extremely metal-poor (EMP) stars in the photometric dataset. A initial survey carried out during telescope commissioning resulted in the discovery of the most iron-poor star known (SMSS J0313-6708) and a further 41 stars with [Fe/H] < -3.0 dex in the Galactic halo. In this contribution we present initial results from a new search for Galactic halo EMP stars based on SkyMapper Survey data. We will discuss the selection process, possible biases, outcomes from the on-going low resolution spectroscopic follow-up program with the ANU 2.3m telescope at Siding Spring Observatory, and initial results from high-dispersion follow-up observations of promising candidates.

### T7, 11:30–11:45 a.m. — An atlas of SFR changes in nearby galaxies from SkyMapper Christian WOLF, The Australian National University

The SkyMapper filter set with its special violet 'v' filter probes the A star contribution in the integrated light of stellar populations at low redshift of z<0.03, relative to both younger and older stars. SkyMapper photometry thus shows whether the star formation rate in a galaxy has recently changed. The diagnostic is similar to H-delta absorption line measurements in IFUs, and its signal peaks 150 Myr after a change in star-formation rate. SkyMapper will provide a galaxy atlas, where local SFR changes are mapped with sub-kpc resolution. The diagnostic works in all NGC/IC galaxies as well as the Fornax and Virgo South Clusters.

### T8, 11:45 a.m. –12:00 p.m. — The SkyMapper High-Redshift Quasar Survey Fuyan BIAN, Australian National University

The luminous quasars at z>5 directly probe the early growth of supermassive black holes and the relation between the formation of early galaxies and black holes. The SkyMapper Southern Survey will cover the whole Southern hemisphere in six optical bands. In this talk, I will highlight one application of the deep Main Survey component, the search for quasars at redshift z>5, and show first results from the released Short Survey data and experimental Main Survey data. We plan to discover bright high-redshift quasars and create a complete sample with massive ancillary-science spectroscopy in Taipan, with the long-term aim of measuring the growth in the black-hole mass function between 750 and 1500 million years after the Big Bang.

### T9, 12:00–12:15 p.m. — Update on the SkyMapper Transient Survey: type Ia supernovae and other transients Anais MÖLLER, Australian National University

The SkyMapper Transient (SMT) survey is performing a rolling search of the southern and equatorial sky utilizing the SkyMapper Telescope at Siding Spring Observatory. Its main goal is to obtain an untargeted sample of type Ia supernovae (SNe Ia) for cosmology. SkyMapper aims to have $>100$, well calibrated, low redshift ($z<0.1$) type Ia supernovae. In addition, the SkyMapper Transient survey aims to discover interesting transients and counterparts for gravitational waves and fast radio burst events. In this talk we will give an update of the SMT survey with a particular focus on supernovae. To date SkyMapper has discovered over 40 spectroscopically confirmed supernovae including 31 Type Ia, SNIa 2016hhd discovered within the first few days of explosion with possible evidence of a shock interaction and, peculiar Type IIn SN 2015J with a triple-peaked light curve. We have participated in the search for optical counterparts of gravitational waves as well as fast radio bursts and other transients including a collaboration with the Deeper, Wider, Faster program. The SkyMapper Transient Survey is in full operation and discovering a large number of transients. The SkyMapper supernovae data set will be valuable as a search and follow-up survey uniformly observed and reduced, and non-targeted sample of low-redshift SNe Ia.

### T10, 12:15–12:30 p.m. — A First SkyMapper Variability Census and the Search for Counterparts to High-energy Events Seo-Won CHANG, The Australian National University

SkyMapper searches for optical counterparts of high-energy events such as fast radio bursts and sources of gravitational waves. The latter involves follow-up observations of more than 100 sq. deg. per event. A large field of view is crucial to deal with the current uncertainties in localisation, but there will be many variable sources contaminating the counterpart candidate list. Here, we present a variability census of the SkyMapper Data Release 1 (DR1) to better understand characteristic timescales and amplitudes of potential contaminants. Several metrics are used to characterize large-amplitude variable sources whose signal can mimic that of a counterpart. We examine the effects of survey depth and cadence of visits for the constraints on the type of variable. We also discuss the variability metrics that we apply to our multi-band, time-series data and provide substantial new data for previously known variables.

### Lunch

Foyer, Crawford School of Public Policy

### The Future of Optical Astronomy in Australia – Sponsored by AAO

Molonglo Theatre

This session will be a discussion of the opportunities provided by Australian membership of ESO, and the ongoing arrangements for AAT operations and the AAO Instrumentation program.

All are welcome.

Molonglo Theatre

### T11, 2:30–2:45 p.m. — Opening the dynamic infrared sky with DREAMS Anna MOORE, Australian National University

While optical and radio transient surveys have enjoyed a renaissance over the past decade, thedynamic infrared sky remains virtually unexplored. The infrared is a powerful tool for probing transient events in dusty regions that have high optical extinction, and for detecting the coolest of stars that are bright only at these wavelengths. The fundamental roadblocks in studying the infrared time-domain have been the overwhelmingly bright sky background (250 times brighter than optical) and the narrow field-of-view of infrared cameras (largest is VISTA at 0.6 sq deg). To address this challenge, we propose a low risk, economical and agile instrument located in an existing housing at Siding Spring Observatory. The proposed Dynamic REd All-sky Monitoring Survey (DREAMS) has the ability to observe the southern hemisphere sky every 25 hours at infrared wavelengths with transient sources released routinely to the community beginning late 2018.

### T13, 2:45–3:00 p.m. — The Huntsman observing systems: the frontier of extremely low surface brightness observations Lee SPITLER, Macquarie University & Australian Astronomical Observatory

Extremely faint, extended structures in the universe contain rich information about astrophysical processes. At the outer edges of galaxies, stellar streams and the halo contain a record of billion years of mass assembly. The cosmic infrared background captures a view of the integrated history of the universe. Sunlight scattered off the dust in our Solar System provides clues about the evolution of planetary systems. And the extended faint envelope of evolved stars provides insight on the chemical pollution of the interstellar medium. In this talk I will describe two facilities designed to access these faint observational targets for the first time. The Huntsman Telephoto Array is an array of off-the-shelf Canon lenses based at Siding Spring Observatory that can explore uncharted low surface brightness regions around galaxies and stars. The Australian Space Eye (‘Huntsman in Space’) is a miniature space telescope concept to monitor the zodiacal light and directly measure the cosmic infrared background.

### T17, 3:15–3:30 p.m. — CACAO: A Cheap And Compact Adaptive Optics system Jamie SOON, Australian National University

Adaptive Optics (AO) corrects for the blurring of images caused by disturbances in the transmission medium. AO is normally thought of as related to correcting for the Earth's atmosphere when capturing astronomical images but it can also be used to correct for aberrations in different systems which occur via other transmission mediums; for example in retinal imaging, horizontal beam propagation, or laser beam cleaning in laboratory applications. The main component of an AO system is the deformable mirror which determines the system cost, specifications, properties and corrective abilities. A Cheap And Compact Adaptive Optics (CACAO) system is currently under development at the ANU which is built around a relatively inexpensive deformable mirror, that has 40 actuators combined with additional tip-tilt capability. This will involve evaluating and characterising the deformable mirror to determine its performance, limitations and potential. The development of CACAO will include testing to determine its capabilities as part of an astronomical AO system and whether the deformable mirror is capable of achieving correction on a telescope in the 1-2m diameter range. Testing will also be undertaken for a range of other scenarios in order to determine the capabilities and other possible applications for the deformable mirror; these different scenarios will include biomedical applications and laser beam cleaning.

### T18, 3:30–3:45 p.m. — LSST and Australia Sarah BROUGH, University of New South Wales

Australian astronomers have access to the Large Synoptic Survey Telescope (LSST) through agreements made by CAASTRO+AAO as well as ICRAR. This is an 8.4m optical survey telescope under construction in Chile. It will survey the Southern Sky to unprecedented depths over a 10-year multi-epoch campaign. I will introduce LSST and the groundbreaking science this survey telescope will undertake and outline ways Australian astronomers can get more involved.

### T20, 3:45–4:00 p.m. — Maunakea melting pot: Opportunities for Australia with EAO Jessica DEMPSEY, East Asian Observatory

The East Asian Observatory has been operating the JCMT on Maunakea for two years. With a focus on international scientific collaboration and the career enhancement of young astronomers, EAO now looks to deepen its portfolio, with an ambitious instrument program for JCMT, as well as new partnerships with leading facilities such as Subaru. Within the changing political and scientific landscape on Maunakea, synergy between Observatories and international collaboration are more critical than ever before. Opportunities for Australia and East Asian regional partnership in instrumentation, science and observatory management will be presented.

Barton Theatre

### T12, 2:30–2:50 p.m. — HI accretion, the Cosmic Web and WALLABY early science Dane KLEINER, CSIRO Astronomy and Space Science

We examine the HI-to-stellar mass ratio (HI fraction) for galaxies in filaments within the nearby Universe (d < 181 Mpc). HI stacking of HIPASS spectra and 6dFGS stellar mass estimates yield the HI fraction for filament galaxies at different stellar masses and projected densities. In an attempt to disentangle what influences cold gas in galaxies, we find galaxies with high stellar masses have a systematically higher HI fraction near filaments than the control sample (Kleiner et al. 2017). I will present the data and discuss evidence for massive galaxies accreting cold gas from the intergalactic medium which can replenish some HI gas. Furthermore I will give an update on the progress of WALLABY Early Science, incl. preliminary results on the nearby spiral galaxy IC 5201 and its environment as revealed after combining multi-epoch ASKAP-12 observations.

### T14, 2:50–3:10 p.m. — Scientific validation of ASKAP continuum data Jordan COLLIER, CSIRO Astronomy and Space Science / Western Sydney University

The Australian Square Kilometre Array Pathfinder (ASKAP) is currently undergoing commissioning, and is continuing to put out high-quality data products. The Evolutionary Map of the Universe (EMU) survey will use ASKAP to produce a deep (~10 uJy rms) radio continuum map of the whole Southern Sky, containing ~70 million radio sources, as compared to the 2.5 million radio sources currently known. EMU Early-Science is well underway, and several key fields have been observed with ASKAP. As part of commissioning, these data need to be validated for science, both for commissioning the instrument and assessing its performance, and for beginning to develop the framework for the automated quality control and scientific verification that will be necessary for EMU. I will discuss the automated pipeline I have developed to produce a science validation report of ASKAP continuum data, the current results and the next steps.

### T16, 3:10–3:30 p.m. — The cold gas reservoir feeding an adolescent radio galaxy James ALLISON, University of Sydney / ASTRO-3D

While some radio galaxies show stong emission lines in the optical, characteristic of an active galactic nucleus, others do not. We have substantial circumstantial evidence that this dichotomy is the result of the mode in which gas is accreted onto the nucleus. However, the exact mechanisms by which high and low excitation radio galaxies are nourished can only be determined through direct observation of the gas. A powerful method for measuring the kinematics of gas deep into the centres of radio-loud AGN is through detection of the HI 21-cm hyperfine and CO rotational lines in absorption. ASKAP, in its commissioning and early science phase, has been very successful in detecting HI absorption in radio galaxies at intermediate cosmological redshifts. In followup observations using ALMA we have detected CO(2-1) absorption in PKSB1740-517, a young powerful radio galaxy at z=0.5. I will discuss the results of this work, including how we can disentangle the line-of-sight ambiguities from absorption and what we learn about the system by combining the ASKAP, ALMA and multiwavelength ancillary data.

### T19, 3:30–3:50 p.m. — The discovery of a population of bright fast radio bursts with the Australia Square Kilometre Array Pathfinder Ryan SHANNON, CSIRO and ICRAR-Curtin

Fast radio bursts (FRBs) remain one of the most exciting and confounding classes of astronomical transients. There is mounting evidence that these bright, dispersed pulses of radio emission originate at cosmological (Gigaparsec) distances. Not only do the energetics of the events point to a new radiative process, but the pulses are imprinted with propagation through the ionised intergalactic medium and cosmic web, making them invaluable probes of media invisible to most other types of observations. Despite considerable effort to detect additional bursts, the yields have been low because of relatively narrow fields of view of most searches. Here I will present the discovery this population from a wide-area survey conducted with the Australia Square Kilometre Array Pathfinder (ASKAP), which leveraged the telescope’s phased-array feeds (PAFs) and utilized a fly’s eye search strategy. I will highlight the discoveries to date, which have yielded three FRBs in ten days of searching, as of the abstract submission, and likely more between then and the conference. I will additionally show how we can use the PAF detections to better localize and measure the fluences of the bursts than other larger telescopes. I conclude by presenting future plans to develop interferometric fast transient capabilities with ASKAP, necessary to harness the full value of FRBs.

### Afternoon Tea

Foyer, Crawford School of Public Policy

Molonglo Theatre

### T21, 4:15–4:30 p.m. — Constraints on the radial extent of debris disks from unresolved continuum emission Jonathan MARSHALL, USQ

Debris disks – tenuous rings of icy and rocky material produced by the breakup of asteroids and/or comets around main sequence stars – are inferred to denote the presence of a planetary system. These disks are most commonly detected through the measurement of excess emission at infrared wavelengths from the host star. In most cases, the emission is spatially unresolved, so the radial extent of the disk is not precisely known. Far-infrared observations of a sample of well-studied, spatially resolved debris disks have revealed a simple relationship between stellar luminosity and disk extent. This scaling can be applied to unresolved debris disks, that comprise the vast bulk of known systems.. Remnant debris marks the outer edge of a planetary system, so we would expected to find planetary companions to the host star interior to the debris disk. Accurate determination of the extent of a large group of planetary systems therefore provides a first glimpse into the range of radial separations at which planet formation may occur. Self-stirring models of disk evolution predict a characteristic outward migration of the disk over time, whereas planetary migration may drive the disk outward more quickly. Comparison of the disk extent derived from observation with self-stirring models will identify those that are anomalously large for their age and therefore may be undergoing a disk-planet interaction. Here I present an analysis of archival Spitzer and Herschel far-infrared observations, both resolved and unresolved, to identify those that are potentially in a phase of disk-planet interaction through migration. I also present a comparison of the stellar luminosity-disk radius relationship derived at far-infrared wavelengths with that based on disk observations at sub-millimetre wavelengths.

### T23, 4:30–4:45 p.m. — The effect of non-ideal MHD on disc winds from protoplanetary discs James TOCKNELL, Macquarie University

Magnetically-driven disc winds have significant effects on the evolution of protoplanetary discs, via the removal of angular momentum and mass from the disc. However, existing models typically ignore non-ideal magnetohydrodynamic effects, such as Hall drift, but these are known to operate inside these discs, and affect their structure and evolution, for example suppressing magnetically-driven turbulence and magneto-rotational instability. In light of this, I will present preliminary results of self-similar disc wind models which include non-ideal magnetohydrodynamic effects within the disc.

### T25, 4:45–5:00 p.m. — Tiny grains shining bright in the gaps of Herbig Ae transition discs Eloise BIRCHALL, Australian National University

Protoplanetary discs exhibit structures such as rings, gaps, asymmetries, and spiral arms, which can be interpreted as signs of planet formation. Around Herbig Ae stars such as Oph IRS 48 and HD 169142, these structures are prevalent in the outer disc regions. In this work, we examine the regions inward of approximately 20AU, where these discs are thought to be mostly cleared of material. We find that there are disc structures and features in these inner regions that are bright in the near-infrared. The inner disc structures are made up of very small dust grains, and in some cases these inner structures could be misinterpreted as planets.

### T27, 5:00–5:15 p.m. — Binary Star Formation and the Outflows from their Discs Rajika KURUWITA, Australian National University

We carry out magnetohydrodynamical simulations with FLASH of the formation of a single, a tight binary (a ~2.5AU) and a wide binary star (a ~ 45AU). We study the outflows and jets from these systems to understand the contributions the circumstellar and circumbinary discs have on the efficiency and morphology of the outflow. In the single star and tight binary case we obtain a single pair of jets launched from the system, while in the wide binary case two pairs of jets are observed. This implies that in the tight binary case the contribution of the circumbinary disc on the outflow is greater than that in the wide binary case. We also fi nd that the single star case is the most efficient at transporting mass, linear and angular momentum from the system, while the wide binary case is an order of magnitude less efficient. The tight binary's efficiency falls between the other two cases, but converges towards the single star case when considering the angular momentum transport. By studying the magnetic field structure we deduce that the outflows in the single star and tight binary star case are magnetocentrifugally driven, whereas in the wide binary star case the outflows are driven by a magnetic pressure gradient.

Barton Theatre

### T22, 4:15–4:30 p.m. — Low luminosity thermonuclear supernovae as the origin of most Galactic antimatter Roland CROCKER, ANU

Our Galaxy hosts the annihilation of a few ×10^43 positrons every second. Radionuclides capable of supplying such positrons are synthesised in stars, stellar remnants, and supernovae. For decades, however, there has been no positive identification of a main stellar positron source. This has led to suggestions that many positrons originate from exotic sources like the Galaxy’s central super-massive black hole or dark matter annihilation, but such sources would not explain the recently-detected positron signal from the extended Galactic disk. We show that a single type of transient source, deriving from stellar populations of age 3-6 Gyr and yielding ∼ 0.03 M⊙ of the positron emitter 44Ti, can simultaneously explain the absolute positron luminosity of the Galaxy and the morphology of the annihilation signal. Our binary population synthesis modelling demonstrates that this transient is likely the merger of two low-mass white dwarfs, likely observed in external galaxies as a particular sub-luminous, thermonuclear supernova, known as SN1991bg-like. [This work has recently been accepted for publication in Nature Astronomy]

### T24, 4:30–4:45 p.m. — Recent Anisotropy Studies With The Pierre Auger Cosmic Ray Observatory Roger CLAY, University of Adelaide

The Pierre Auger Observatory is the world’s largest cosmic ray observatory. It has been in full operation for almost a decade, giving it the largest ever exposure at ultra-high energies. The Auger dataset at those highest energies is large enough to enable astrophysically significant studies to be made of both broad-scale and hot-spot anisotropies in the southern sky. Through the selection of particular classes of events, searches can also be made for point sources associated with uncharged messengers. Recent Auger anisotropy data will be presented together with discussion of their possible astrophysical interpretation.

### T26, 4:45–5:00 p.m. — Detecting high-energy cosmic particles with radio telescopes Clancy William JAMES, Curtin University

The 'radio-particle' technique allows radio telescopes to study the highest-energy cosmic rays and neutrinos. When these particles interact in a medium, they produce a nanosecond burst of emission that can be detected in the MHz-GHz regime. Advances in both digital signal processing technology and the theory of the emission have led to a recent surge in experimental activity using this technique. In particular, it has allowed LOFAR to make the most precise measurements of cosmic ray composition near 10^17 eV, and Parkes and others to limit the flux of extremely energetic neutrinos. After briefly reviewing the status of the field, possibilities for groundbreaking observations of cosmic rays in the Earth's atmosphere and on the Moon with the MWA, ASKAP, and Parkes will be described. Finally, the technique is now the focus of the Square Kilometre Array's High Energy Particle Focus Group, and I will outline plans to detect an unprecedented number of ultra-high-energy cosmic rays, and study extensive air showers with ultimate precision.

### T28, 5:00–5:15 p.m. — A quantum of darkness: making particles invisible Allan ERNEST, Charles Sturt University

Understanding the nature and origin of dark matter remains one of the greatest challenges facing modern astronomy and cosmology. The leading theoretical paradigm, Lambda Cold Dark Matter (LCDM), works well on the largest scales but encounters significant issues on the cluster scale and below, and additionally requires the existence of an as-yet-undiscovered particle. Quantum theory however, could solve the dark matter problem entirely, without the need for new particles or new physics, and without compromising the previous successes of LCDM. Quantum analysis of the interaction properties of baryonic particles in ‘sloping’ gravity wells shows that photon-particle cross sections can vary, depending on particle environment and that, in large deep-gravity wells, these cross sections can be much less than currently accepted values [1,2]. This purely quantum phenomenon provides an effective and unassailable solution to the dark matter problem within the LCDM framework. Additionally, a primordial formation scenario [1,3] potentially enables an “all-baryonic” universe to be observationally compliant with primordial nucleosynthesis ratios, galaxy distributions and microwave anisotropy observations, the pillars of observation that have previously required the need for a new “dark” particle. In this talk I will discuss the quantum solution to the dark matter problem. [1] Ernest, A D 2006, in Dark Matter: New Research, ed. J. Val Blain, NOVA Science, N.Y. ISBN: 1-59454-549-9 [2] Ernest A. D., 2009, J. Phys. A: Math. Theor. 42 115207, 115208 [3] Ernest A. D., and Collins, M.P., 2015, Proceedings of the International Astronomical Union, 11, pp 298-299. doi:10.1017/S1743921315006894

## Tue, 11 Jul

### ESO Agreement Signing

8:00 a.m. – 9:15 a.m. @ Crawford School of Public Policy

To celebrate the creation of a strategic partnership between the Australian astronomical community and European Southern Observatory, all Annual Scientific Meeting participants are invited to two events:

• An ESO Signing Breakfast will be held in the foyer of the Crawford School of Public Policy from 8.00-8.30am;
• The Signing ...

Molonglo Theatre

### T29, 9:15–9:45 a.m. — Triggering AGN in galaxy clusters (Bok Prize talk) Madeline MARSHALL, University of Melbourne

⇒ This talk is by the winner of the Bok Prize

Active galactic nuclei (AGN) play an important role in the regulation of star formation in their host galaxies and the larger scale environment. To develop a full understanding of the role of AGN, it is important to know how they are triggered. Using a semi-analytic galaxy evolution model, I investigate the predicted spatial distribution of AGN in clusters under the assumption that they are triggered by ram pressure effects. By comparing these simulated AGN to SDSS observations of relaxed clusters, I find that the observed AGN distribution can be reproduced well by ram pressure triggering, with triggering ram pressures consistent with those found to trigger star formation in hydrodynamical simulations. These findings may assist in the interpretation of cluster observations including deep multi-wavelength and integral field surveys.

### T30, 9:45–10:00 a.m. — The relationship of AGN feedback by relativistic jets to the spectra of Gigahertz Peak Spectrum and Compact Steep Spectrum radio sources Geoffrey BICKNELL, Research School of Astronomy & Astrophysics, Australian National University

Our program of 3D simulations of relativistic jets interacting with inhomogeneous interstellar media determines the resultant velocity and distribution of dense gas and the distribution of non-thermal plasma. We have utilized these simulations to determine the signatures of these interactions in the associated radio emission. Free-free absorption by the surrounding dense gas produces a turnover in the radio spectrum. The low frequency spectrum is initially steep, consistent with some spectra in the recent compilation of MWA spectra by Callingham et al. (2017). However, the spectra become flatter as the source evolves as a result of the broad distribution of optical depths produced by the jet-ISM interaction. The range of spectral indices is consistent with that of Gigahertz Peak Spectrum (GPS) and Compact Steep Spectrum (CSS) sources. Moreover, the evolution of the turnover frequency is consistent with the observed anti-correlation between turnover frequency and source size discovered by Fanti et al. (1995) and O’Dea and Baum (1997). These results indicate that further studies of GPS and CSS sources can shed significant light on the physics of AGN feedback.

### T31, 10:00–10:15 a.m. — Catching Feedback in the Act at the Sub-kpc Scale Anna ZOVARO, The Australian National University

Powerful jets emerging from the black holes in active galactic nuclei (AGN) interact with the interstellar medium (ISM) as they leave the nucleus, dramatically influencing the evolution of the host galaxy. In particular, star formation is thought to be either enhanced (positive feedback) or suppressed (negative feedback) by this process. Simulations have shown that both positive and negative feedback processes may occur; however, the dominant feedback mechanism is influenced by both the precise structure of the ISM and the power of the jet, making it difficult to predict which mechanism will dominate, and in turn whether overall star formation is enhanced or suppressed. Gigahertz Peak Spectrum (GPS) and Compact Steep Spectrum (CSS) sources are young radio sources with compact and often distorted morphologies resulting from the interaction of jets with a dense, inhomogeneous ISM. Potential progenitors to FR I & II radio sources, GPS/CSS sources are believed to be in an intermediate stage of evolution in which the jets have not yet broken free of the ISM and are actively suppressing or enhancing star formation. Spatially resolved observations of GPS and CSS sources on the kpc scale can therefore provide us with a valuable insight into these jet-ISM feedback processes. We present NIFS H- and K-band spatially-resolved integral field spectroscopy of the two radio sources 4C31.04 and 4C14.82. The morphology, structure and kinematics of the central gas has been analysed in conjunction with indicators of current and historical star formation to search for signatures of positive or negative feedback.

### T32, 10:15–10:30 a.m. — DRAGONS: AGN quenching of high redshift star formation in ZF-COSMOS-20115 Yuxiang QIN, The University of Melbourne

Massive quiescent galaxies are thought to have formed stars rapidly at early times followed by a long period of quiescence. The recent discovery of a massive (∼1e11M⊙) quiescent galaxy, ZF-COSMOS-20115 at z ∼ 4, only 1.5 Gyr after the Big Bang, places new constraints on galaxy growth and the role of feedback in early star formation. In this talk, I will present the study of three ZF-COSMOS-20115 analogues in the DRAGONS programme, identified using the Meraxes semi-analytic model. We investigate how ZF-COSMOS-20115 analogues build stellar mass, and why they become quiescent. We find that ZF-COSMOS-20115 is likely hosted by a massive halo with virial mass of ∼1e13M⊙, having been through significant mergers at early times. These merger events drove intense growth of the nucleus, which later prevented cooling and quenched star formation. We find that the analogues host the most massive black holes in our simulation and were luminous quasars at z ∼ 5, indicating that ZF-COSMOS-20115 and other massive quiescent galaxies may be the descendants of high redshift quasars.

### T33, 10:30–10:45 a.m. — Using Broad Absorption Lines to Illuminate Quasar Structure Suk Yee YONG, The University of Melbourne

The characteristics of the spectral lines in quasars reveal information about the structure and kinematics of the broad emitting line region (BELR). A small fraction of quasars displays signature of broad absorption line (BAL) with deep absorption trough blueshifted relative to the broad emission line (BEL). This is often interpreted as a consequence of either the evolutionary or the orientation based unification models. In order to test these schemes, samples from the Sloan Digital Sky Survey are used to examine the properties of ultraviolet BELs in BAL and non-BAL quasars. Although statistical differences are found between the two populations, they exhibit rather similar BEL trends. Results from statistical analysis shows that both models are unable to completely account for the observed trends. This analysis is used to develop a new model of the quasar BELR.

### Poster Sparklers (1)

Molonglo Theatre

Poster numbers 1-15

### Morning Tea

Foyer, Crawford School of Public Policy

Molonglo Theatre

### T34, 11:30 a.m. –12:00 p.m. — Stellar Astrophysics with Cassini: Syzygies, Stardust and the Sizes of Stars (Charlene Heisler Prize talk) Paul STEWART, Sydney Institute for Astronomy

⇒ This talk is by the winner of the Charlene Heisler Prize

The multi-national, multi-billion-dollar, Cassini mission has resulted in amazing insights into the complex Saturn system, dramatically improving our understanding of the planet, and its moons and rings. One particularly successful method employs the observation of bright stars as the planet's rings pass in front, allowing the study of the ring system. In this presentation I will demonstrate how such observations can also be used to investigate the stars themselves.

The technique is shown to be effective for measuring the spatial and spectral structure of evolved stars, including identification of molecular layers in the stellar atmosphere. It enables the recovery of high-angular-resolution 2D images of the inner regions of complex stellar systems, achieving resolutions not possible with regular telescopes. These observations are demonstrated to help constrain models of the behaviour of Mira variable stars, and to change our understanding of the inner nebula around IRC+10216.

### T35, 12:00–12:15 p.m. — Detection of young stars in the large spectroscopic surveys Marusa ZERJAL, Australian National University

Chromospheric activity is a suitable age estimator for young solar-like and cooler main sequence field stars. It manifests itself in a wide range of excess emission intensities in the strongest spectral lines. While precise dating is not possible, an order of magnitude age estimate is easily attainable from a single spectral measurement with a moderate signal-to-noise ratio and mid-range resolving power in the range from a few tens of millions of years up to a few gigayears. Today, in the era of large spectroscopic surveys targeting magnitude-limited samples, it is possible to identify a substantial number of young stars in the Solar neighbourhood with efficient unsupervised classification algorithms. In the RAVE Survey, covering over 500,000 calcium infrared triplet (Ca II IRT) spectra of more than 480,000 stars, this approach in a combination with a model-free emission measure yielded over 13,000 stars younger than 1 Gyr and almost 2000 stars younger than 100 Myr in the Solar neighbourhood (distance less than 200 pc). The strongest support for their young ages is their position in the pre-main sequence region in the color-magnitude diagram using the Gaia DR1 distances with less than 10% relative errors. Their X-ray emission is in favour of this hypothesis. The sample will be significantly extended in the future, e.g. the Galah survey will observe 1 million stars. The FunnelWeb survey, a new ambitious project with aim to cover 3 million stars down to magnitude 12 will focus on young and adolescent stars. The age estimates using the emission in the Ca II IRT and the stronger Ca II H&K lines will be improved with the Lithium 6708A line. Because the innovative TAIPAN spectrograph and the starbugs fiber positioner system will enable observations of the bright stars as well, the combination of their ages and stellar orbits using the Gaia distances and proper motions will hold a huge potential not only for the recent nearby star formation events but also for the studies of young exoplanets and their environments around the nearest stars.

### T36, 12:15–12:30 p.m. — Polarisation due to rotational distortion in the bright star Regulus Daniel Vincent COTTON, University of New South Wales

We report the first detection of polarised light due to rotational distortion in a rapidly rotating hot star, an effect first predicted nearly fifty years ago. Observations of the linear polarisation of Regulus, with two different high-precision polarimeters, range from +42 parts per million at a wavelength of 741 nm to –22 parts per million at 395 nm. The reversal from red to blue is a distinctive feature of rotation-induced polarisation. Using a new set of models for the polarisation of rapidly rotating stars we report determinations for the angular velocity, inclination, gravity and effective temperature of Regulus, as well as the position angle of the rotation axis. The conclusions are independent of, but in good agreement with, the results of interferometry. This result represents a watershed moment for stellar linear polarimetry. Previously the field has been largely restricted to studying extreme magnetic fields or material external to stars. Now we are able to probe fundamental parameters of the stellar atmosphere itself.

### T37, 12:30–12:45 p.m. — Observations of radio stars with geodetic VLBI Oleg TITOV, Geoscience Australia

Some stars have radio emission that is strong enough to be detected by geodetic VLBI facilities. Observations of these radio stars were used to link the Hipparcos (optical) and VLBI (radio) celestial reference frames in 90s. The new optical catalogue currently being compiled by Gaia will allow a more advanced link between the optical and radio reference frames to be developed. Radio stars present a good tool to calibrate the proper motions and parallaxes with high accuracy. The first results from a program to observe radio stars with the large geodetic VLBI network, which includes the Parkes and Hobart radio telescopes, are presented.

### T38, 12:45–1:00 p.m. — Chasing Low Frequency Radio Bursts from Magnetically Active Stars Christene LYNCH, University of Sydney/CAASTRO

Flaring activity is a common characteristic of magnetically active stars. These events produce emission throughout the electromagnetic spectrum, implying a range of physical processes. A number of objects exhibit short-duration, narrow band, and highly circularly polarised (reaching 100%) radio bursts. The observed polarisation and frequency-time structure of these bursts points to a coherent emission mechanism such as the electron cyclotron maser. Due to the stochastic nature of these bursts and the sensitivity of current instruments, the number of stars where coherent emission has been detected is few, with numbers limited to a few tens of objects. Observations of a wider sample of active stars are necessary in order to establish the percentage that exhibit coherent radio bursts and to relate the observed emission characteristics to stellar magnetic properties. New wide-field, low frequency radio telescopes will probe a frequency regime that is mostly unexplored for many magnetically active stars and where coherent radio emissions are expected to be more numerous. M dwarf stars are of particular interest as they are currently favoured as most likely to host habitable planets. Yet the extreme magnetic activity observed for some M dwarf stars places some doubt on the ability of orbiting planets to host life. This presentation reports the first results from a targeted Murchison Widefield Array survey of M dwarf stars that were previously detected at 100 - 200 MHz using single dish telescopes. We will discuss robust flare-rate measurements over a high dynamic range of flare properties, as well as investigate the physical mechanism(s) behind the flares.

### Lunch

Foyer, Crawford School of Public Policy

Barton Theatre

### IDEA Chapter Meeting – Sponsored by CAASTRO

Molonglo Theatre

At this year's IDEA lunch meeting (Tuesday 11 Jul, 1.15pm in Molongolo Theatre) we will be presenting the 2016 Pleiades Award certificates, hearing from the 2016 Gold award winners, CAASTRO, and hearing updates to the selection criteria for the 2018 Pleiades Award.

Molonglo Theatre

### T39, 2:15–2:30 p.m. — An update on the MWA EoR Experiment Jack LINE, University of Melbourne

In this talk I will give an overview on the current status of the Epoch of Reionisation (EoR) experiment using the Murchison Widefield Array (MWA), which attempts to use cosmologically red-shifted HI emission to trace the first luminous sources in the Universe. I will highlight some of our current focus areas, such as the exquisite understanding of the telescope necessary for a detection, how well we must understand our astrophysical foregrounds and how to remove them, the effects of the ionosphere on data and polarisation, and the possible applications of redundant calibration. Throughout, I will discuss successes and progress by the collaboration to date in trying to overcome these challenges, and the current status of our analysis.

### T41, 2:30–2:45 p.m. — Toward the Epoch of Reionisation: challenges and progress on the path to the Early Universe Cathryn TROTT, ICRAR - Curtin University

The Cosmic Dawn and Epoch of Reionisation mark two crucial epochs in the formation and growth of structure in the first billion years of the Universe. Providing a bridge between the small temperature fluctuations of the CMB and structured and luminous Universe of low redshift, these epochs trace the formation and illumination of the first ionising sources of radiation, and the ionisation of the intergalactic medium. Observation of the redshifted 21-cm emission line from neutral hydrogen is a promising probe of this period, the signal of which encodes astrophysical and cosmological information. This project is particularly important for Australia, with ongoing experiments with the Murchison Widefield Array (MWA), and future host of the Square Kilometre Array (SKA). Despite its promise, detection of the signal, and study of its structure, has thus far eluded low-frequency radio telescopes. This talk discusses the challenges involved in this experiment, and the advances made over the past five years for peeling away the systematics and reaching the signal.

### T43, 2:45–3:00 p.m. — Challenging EoR Challenges with Array Redundancy Ronniy JOSEPH, Curtin University

The formation of the very first objects was accompanied by the ionisation of their surroundings and ultimately the entire Universe. This period, in which the Universe underwent this large phase change, is known as the Epoch of Reionisation (EoR), and studying it will reveal what the first objects actually were. The advent of a new generation of low frequency radio interferometers, e.g. LOFAR, the Murchison Widefield Array (MWA), and the future Square Kilometre Array, has opened a direct window into the EoR. With these telescopes we can gain insight into the cosmology and astrophysics driving structure formation in the Early Universe by studying fluctuations in the 21-cm signal emitted by neutral hydrogen. The signal is, however, hidden in foregrounds that are estimated to be 4 magnitudes stronger. In this talk I will describe the challenges of signal detection, and discuss how novel calibration strategies are crucial to its success. I will describe work I am undertaking to use the design of the MWA to improve calibration, including combining redundant and non-redundant baselines, and optimally using the information available in the data.

### T45, 3:00–3:15 p.m. — Modelling High-z Galaxy Formation and the EoR with semi-analytics Simon MUTCH, The University of Melbourne

Simultaneously modelling high-redshift galaxy formation and large scale cosmic reionization is a difficult task, but an essential one if we hope to fully leverage the combined results of future radio and IR observations. In this talk I will discuss semi-analytics as a useful and powerful compliment to other simulation methods for studying the EoR. I will then introduce Meraxes, the first semi-analytic galaxy formation model to include a temporally and spatially coupled treatment of galaxy growth and reionization. I'll also demonstrate the success of this model in reproducing a number of key observables, as well as examples of some of its predictions for galaxy sizes, and the relative importance of photo-ionisation feedback on galaxy growth. Finally, I'll discuss possible ways in which we can exploit models such as Meraxes in the future, in particular focussing on the connection between high redshift physics and low redshift/mass observations.

### T47, 3:15–3:30 p.m. — Exploring Reionization With Semi-Analytics: The Escape Fraction Strikes Back Jacob SEILER, Swinburne University

The Epoch of Reionization is a pivotal period in our cosmic history, representing the transition from a neutral post-recombination Universe into the fully ionized one we observe today. The procession of reionization is dictated by the fraction of ionizing photons, $f_\mathrm{esc}$, that escape from galaxies to ionize the inter-galactic medium, with the exact value and functional form still an open question. I explore this question using a cosmological galaxy formation model to predict the number of ionizing photons emitted, coupled with a sophisticated semi-numerical code to follow different possible Epoch of Reionization scenarios. Specifically, I investigate how changing $f_\mathrm{esc}$ affects the progress of reionization, measuring its impact on properties such as the overall duration from neutral to fully ionised, and the size of the ionised bubbles within the cosmic gas. Such predictions, when combined with future observations, will provide powerful constraints on the early evolution of gas and galaxies in the Universe.

### T49, 3:30–3:45 p.m. — Bubbles at dawn Paul Michael GEIL, The University of Melbourne

Direct detection of regions of ionised hydrogen (HII) has been suggested as a promising probe of cosmic reionisation. Observing the redshifted 21-cm signal of hydrogen from the epoch of reionisation (EoR) is a key scientific driver behind new-generation, low-frequency radio interferometers. We investigate the feasibility of combining low-frequency observations with the Square Kilometre Array and near infra-red survey data of the Wide-Field Infrared Survey Telescope to detect cosmic reionisation by imaging HII bubbles surrounding massive galaxies. While individual bubbles will be too small to be detected, we find that by stacking redshifted 21-cm spectra centred on known galaxies, it will be possible to directly detect the EoR at z ~ 9–12, and to place qualitative constraints on the evolution of the spin temperature of the intergalactic medium (IGM) at z > 9. In particular, given a detection of ionised bubbles using this technique, it is possible to determine if the IGM surrounding them is typically in absorption or emission. Determining the globally-averaged neutral fraction of the IGM using this method will prove more difficult due to degeneracy with the average size of HII regions.

Barton Theatre

### T40, 2:15–2:30 p.m. — The FunnelWeb Survey: Exoplanet and Galactic Science in the Gaia Era Michael IRELAND, Australian National University

The FunnelWeb survey with the TAIPAN spectrograph will begin in September this year, and will become the southern hemisphere's largest spectroscopic survey. FunnelWeb will target all stars (away from the most crowded regions) brighter than Gaia G=12, as well as selected fainter samples. I will describe the key science drivers of the survey, including TESS planet host spectra, local Galactic archaeology and a complete census of nearby young stars. I will show results from tiling simulations of the sky, demonstrating how these science goals will work together, and we will maintain a novel, adaptable prioritisation. Finally, I will describe the preferred machine learning stellar parameters approach of semi-supervised local tangent space alignment, which will be used to obtain calibrated physical parameters across the HR diagram.

### T42, 2:30–2:45 p.m. — Astrophysical Standards for FunnelWeb’s Label-based Stellar Parameter Pipeline Adam RAINS, AUSTRALIAN NATIONAL UNIVERSITY

The FunnelWeb Survey, using the TAIPAIN instrument on the UK-Schmidt telescope at Siding Spring Observatory, seeks to create a new database of spectra for every Southern Hemisphere star down to 12th magnitude. FunnelWeb will grow the number of stars with high-quality (S/N~100), moderate resolution (R~2000) spectra available in a calibrated and on-line database. The main goals of the survey include a spectral library with detailed stellar parameters (including Teff, log(g), [Fe/H] and [alpha/Fe]), an input catalogue for the TESS satellite, and identifications of young stars through Li. This talk details requirements and processes for selecting stellar standards to serve as the basis for FunnelWeb’s label based stellar parameters pipeline.

### Afternoon Tea

Foyer, Crawford School of Public Policy

### Introduction To Machine Learning

Registration required

4:00 p.m. – 8:00 p.m. @ Griffin Seminar Room

Run by Astronomy Data and Computing Services (ADACS), this workshop will introduce machine learning concepts, where possible showing astronomy examples.

The introduction is followed by a hands-on session on designing basic machine learning workflows for supervised and unsupervised learning approaches, classification and regression methods and model tuning.

There ...