Tenure-track position

Apply – deadline Monday, 16 Oct 2017
The School of Physics at the University of Melbourne is seeking the appointment of an outstanding female academic to a continuing (tenure-track) position of Lecturer or Senior Lecturer in astrophysics. The successful applicant will also be awarded an ASTRO 3D Fellowship within the ARC Centre of Excellence for All Sky Astrophysics in 3-Dimensions (ASTRO 3D), which allows for full time research during the first six years of the appointment.

ASTRO 3D spans six (6) Australian universities, three (3) national infrastructure facilities, and seven (7) international partner institutions. ASTRO 3D combines Australia’s leading optical, infrared and radio telescope technologies with sophisticated theoretical simulations and ambitious new data intensive science techniques to build a comprehensive picture of the evolution of matter, the chemical elements, and ionizing radiation in the Universe from the Epoch of Reionization to the present day.

The position is open to female researchers in any area of ASTRO 3D science. The appointee is expected to attract postgraduate students, engage collaborative links, and secure competitive research funding. The lecturer will supervise research students at MSc and PhD levels. At the conclusion of their ASTRO 3D fellowship, they will also have a core commitment to teaching within the School’s undergraduate and MSc programs.

The University seeks to increase the representation of women in areas where they have been traditionally under-represented. Pursuant to a Special Measure under Section 12 (1) of the Equal Opportunity Act 2010 (Vic), The School will, therefore, only consider applications from suitably qualified female candidates for this position.



Applications of Machine Learning in Stellar Astrophysics

Wed 12 December, 2018 @12:00 PM, level 7
Dr George Angelou, MPA

Email:  gangelou[at]mpa-garching.mpg.de

Abstract

Astronomy is now very much a big-data science. Gaia has had its second data release and is on track to measure the brightness, position and kinematics of close to 109 stars. TESS and PLATO will observe pulsations in > 105 targets. They will add to the approximately 2×105 that have had their oscillations monitored by Kepler and CoRoT. To exploit such large data sets the tools of analysis devised must demonstrate speed, accuracy and versatility. Speed and accuracy are required to process the sheer volume of data collected. Versatility is necessary because although there will be overlap in the many surveys, not all stars will have the same quantities measured. It is paramount that methods are designed to handle missing or inhomogeneous data sets — we must maximize the information extracted from the available observations. I will discuss the Stellar Parameters in an Instant Pipeline (SPI) which is a machine learning algorithm that makes use of detailed asteroseismic observations to rapidly and robustly determine stellar parameters. Stellar parameters are important for both exoplanet and galactic astrophysics.


The role of turbulence, magnetic fields and feedback for star formation

Wed 05 December, 2018 @11:30 AM, level 6
Dr Christoph Fedderath, ANU

Email:  christoph.federrath[at]anu.edu.au

Abstract

Turbulence and magnetic fields determine the structure of the interstellar medium. In recent years we have developed a theoretical model of how this turbulence, magnetic fields, and feedback control the star formation rate. A critical step towards this theory is to understand the filamentary structure of molecular clouds and which physical processes give rise to the dense filaments within them. Here we show that the transition from supersonic to subsonic turbulence — the sonic scale — may determine crucial properties of the filaments, such as their widths, and how the sonic scale enters our derivation of star formation rates. I will also present results from the world’s largest supersonic turbulence simulation, in which we measure the sonic scale, from which the the filament width and critical density for star formation is derived.


Neutron Stars as Cosmic Laboratories

Wed 28 November, 2018 @12:00 PM, level 7
Dr Vanessa Graber McGill Space Institute, McGill University

Email:   vanessa.graber[at]mcgill.ca

 

Abstract

Neutron stars unite many extremes of physics which cannot be reached on Earth, making them excellent cosmic laboratories for the study of dense matter. One exciting example is the presence of superfluid and superconducting components in mature neutron stars. When developing mathematical models to describe these large-scale quantum condensates, physicists tend to focus on the interface between astrophysics and nuclear physics. Connections with low-temperature physics are often ignored. However, there has been dramatic progress in understanding and experimenting with laboratory condensates (from the different phases of superfluid helium to the entire range of superconductors and ultra-cold gases). In this talk, I will provide an overview of what we know about superfluid and superconducting components in neutron stars, and suggest novel ways that we may make progress in understanding neutron star physics using the connections to terrestrial low-temperature condensates.

 


Integral-field spectroscopy of galaxies

Mon 19 November, 2018 @2:15 PM, level 7
Professor Tim de Zeeuw, Leiden Observatory & Former Director General at ESO

Email:  dezeeuw@strw.leidenuniv.nl

Abstract

The talk will briefly outline the development of optical integral-field spectroscopy and its application to the study of galaxies. It will highlight some of the key achievements and include initial results for the galaxies in the core of the nearby Fornax cluster of galaxies obtained with the transformational MUSE instrument on the Very Large Telescope as part of the F3D project.


Newtonian noise studies for future generation gravitational-wave detectors

Wed 14 November 2018 @12:00 PM, level 6
Dr. Pat Meyers University of Melbourne

Email:  pat.meyers[at]unimelb.edu.au

 

Abstract

Second generation gravitational wave (GW) detectors like Advanced LIGO and Advanced Virgo have ushered in the era of gravitational wave astronomy and multi-messenger astronomy with several detections of compact binary mergers. One of the next frontiers of GW astrophysics is to detect and to characterize the stochastic gravitational wave background (SGWB). A measurement of an astrophysical SGWB (like that caused by many unresolved compact binary mergers) could happen in the next few years with second generation detectors, but the ability to detect relic GWs, like those produced in many models of the early Universe, with third generation ground-based interferometric detectors will require significant improvements in strain sensitivity at frequencies below ~10 Hz. In this talk, I will broadly discuss the challenges in improving sensitivity at low frequencies before focusing on noise caused by local gravitational perturbations, known as Newtonian noise. Newtonian noise can be caused by density fluctuations in the Earth (seismic waves) and the atmosphere (density and temperature fluctuations) and current estimates suggest that it will likely be a limiting noise source for future GW detectors at low frequencies. I will discuss a 3-dimensional seismometer array at the former Homestake gold mine in Lead, SD, whose primary goal is to estimate and better understand Newtonian noise, and to develop techniques for mitigating it in future GW detectors. Along the way, I’ll also introduce some basic seismology, and highlight how some of our results are useful to the broader seismological community.


Cosmoclimatology – How cosmic rays connect to clouds and climate

Mon 12 November 2018 @11:30 AM, level 6
Jacob Svensmark Niels Bohr Institute

Email:  jacob.svensmark[at]nbi.ku.dk

 

Abstract

It has been suggested that our local galactic environment, through cosmic rays, can affect our terrestrial climate. Remarkable correlations between cosmic rays and climate have been observed across timescales stretching from weeks to galactic years, but only last year an actual microphysical mechanism relating cosmic rays to cloud formation was demonstrated in the lab. This finding substantiates that the solar system is not merely evolving inside an isolating bubble in its host galaxy, but a spaceship experiencing and reacting to its local galactic environment.


How to tackle a giant Star: multi-wavelength studies of cool, evolved stars using HST and VLTI

Thurs 8th November, 2018 @15:30 PM, level 6
Dr Gioia Rau, NASA Goddard Space Flight Center

Email:   gioia.rau[at]nasa.gov

 

Abstract

The chemical enrichment of the Universe is considerably affected by the contributions of Giant stars. K-M giant and supergiant stars are surrounded by a hot layer called the chromosphere, which likely powers Magneto-Hydrodynamic Alfven waves that drive their mass loss. Toward the end of their life, on the Asymptotic Giant Branch (AGB), stars produce heavy chemical elements, molecules, and dust, which, through the mass loss provided via their stellar winds, are placed into the interstellar medium.

This talk will explore ongoing work modeling high-resolution spectroscopic observations with Hubble Space Telescope instruments (Rau et al. 2018, subm.), to reveal the role of the chromosphere in driving K-M giant and supergiant winds. Our results include estimates of wind and chromospheric parameters, mass-loss rates, and fundamental stellar parameters.

In addition, ground-based interferometric measurements with high-angular resolution instruments from VLTI, such as MIDI (Rau et al. 2015, Rau et al. 2017) and GRAVITY (Wittkowski et al. 2018), helped to test geometrical and dynamical models describing the behavior of the outer AGB atmospheres at various spatial scales. In this way we are able to unravel the role of molecules and dust in their extended atmospheres.

Future plans include the use of high-angular resolution instruments such as VEGA at CHARA, and MATISSE at VLTI, to better understand the behavior of cool stars outer atmospheres at various spatial scales.

 


MeerKAT inaugurated

Wed 7 November 2018 @14:00 PM, level 6
Dr. Marisa Geyer Square Kilometer Array, South Africa

Email:  mgeyer[at]ska.ac.za 

 

Abstract

Just two years after its first light, on the 13th of July this year, the MeerKAT telescope was inaugurated by the South African deputy president in Carnavon, in the remote Northern Cape of South Africa.

The inauguration showcased the first science quality data flowing out of the full 64 antenna interferometeric array, (operating in 4096 channel mode at L-band), by unveiling a detailed panorama of the Galactic Centre. This important internal milestone has exhibited both the sensitivity and the potential of the MeerKAT telescope, which is increasingly ‘open for business’.

To have the instrument working at its full capacity, much commissioning work remains to be done. As a member of the beamformer commissioning team, I will provide an overview of the MeerKAT telescope and the goals achieved in the run up to the inauguration event. I will also map the road ahead – pointing to exciting developments since the inauguration and the remaining challenges.


Fundamental Limitations on the Calibration of Redundant 21-cm Cosmology Instruments

Fri 2 November 2018 @12:00 PM, level 6
Ruby Byrne University of Washington

Email:  rlbyrne[at]uw.edu

 

Abstract

Precise instrument calibration is critical to the success of 21-cm Cosmology experiments. In recent years, redundant calibration has emerged as a potential solution to calibration errors associated with an incomplete sky model. We show that redundant calibration, like traditional sky-based calibration, is susceptible to errors from sky model incompleteness. These errors contaminate the Epoch of Reionization (EoR) signal and can preclude a measurement.

Astrophysical foregrounds are 4-5 orders-of-magnitude brighter than the cosmological signal, but because they are spectrally smooth they are in principle separable. Unmitigated calibration errors can couple bright foreground emission to higher power spectrum modes, making an EoR signal detection impossible. Barry et al. 2016 identifies one class of systematic errors that emerge from calibrating to an incomplete sky model (N. Barry et al., Mon. Not. R. Astron. Soc., 461, 2016). Missing sources in the sky model, along with their associated point spread functions, introduce chromatic calibration errors that contaminate the power spectrum modes sensitive to the EoR.

Barry et al. 2016 explored these errors in the context of sky calibration, but it has been unclear if they also affect the calibration of redundant arrays. We present a mathematical framework to show that redundant calibration is vulnerable to errors from sky model incompleteness that emerge in the “absolute calibration” step, in which degenerate calibration parameters are calculated from a sky model. Using end-to-end power spectrum simulations with idealized radio arrays and sky models, we show that these errors can prevent an EoR detection even in the limit of perfect array redundancy and no thermal noise. Finally, we suggest error mitigation strategies with implications for the Hydrogen Epoch of Reionization Array (HERA) and the Square Kilometre Array (SKA).

 


Space Weather: How space affects our day-to-day life

Wed 31 October, 2018 @12:00 PM, level 7
Dr. Julie Currie RMIT

Email:  julie.currie[at]rmit.edu.au

 

Abstract

The field of Solar-Terrestrial Physics is concerned with the interaction between our Sun, the interplanetary medium and Earth. The solar wind is a constant outflux of material from the Sun which interacts with Earth’s magnetic field driving a dynamic system in the near-Earth space. As the world becomes heavily reliant on new technologies the effect of space weather is increasing rapidly. This talk focuses on the dynamics of the near-Earth space and how these dynamics cause problems with our technological assets such as power grids, satellite communications and surveillance technologies. One example of disruption to satellite communications is Equatorial Plasma Bubbles (EPB) which occur in the post-sunset ionosphere. The talk will conclude with some details regarding the current forecasting capabilities and the on going efforts in understanding these plasma irregularities.


The stellar kinematics and star-formation histories of high-redshift galaxies

Wed 24 October, 2018 @12:00 PM, level 7
Dr Trevor Mendel, ANU

Email:  trevor.mendel[at]anu.edu.au

Abstract

Galaxies’ integrated continuum spectra provide a powerful tool with which to study their formation and evolution. While observations of stellar absorption lines have historically been limited to a handful of objects in the high-redshift Universe, state-of-the-art near-infrared spectrographs have now allowed us to obtain deep rest-frame optical spectra for nearly 60 quiescent galaxies out to z = 2 with signal-to-noise suitable to study their kinematics and stellar populations. I will highlight a number of recent results based on using galaxy kinematics to constrain the evolution of quiescent galaxies and their dark matter haloes, as well as discuss the prospects of obtaining more detailed information about their formation histories from stellar population models.


Observing the birth of planets

Wed 17 October, 2018 @12:00 PM, level 7
Dr Valentin Christiaens Monash University

Email:  valentin.christiaens[at]monash.edu

 

Abstract

n order to solve the puzzle of the origin of the exoplanets and the Solar System, it is necessary to observe on-going planet formation. The young gas- and dust-rich circumstellar disks, also called protoplanetary disks, are the expected birthplace of planets. A fraction of these disks, referred to as transition disks, were identified to harbor inner clearings in their dust distribution, with some of these gaps extending over several dozens au, possibly due to dynamical carving by nascent giant planets.


Here I will first provide a brief description of state-of-the-art high-contrast imaging techniques, and then discuss results obtained from their application to the search of direct signals from protoplanets in transition disks. I will also explain how the characterization of structures seen in transition disks (e.g. gaps, spiral arms) and disk kinematics can be used to provide independent mass constraints on young embedded companions. A brief overview of promising techniques and instruments for the field of planet formation will also be provided.


The Exterior Spacetime of Relativistic Stars in Quadratic Gravity

Wed 10 October 2018 @12:00 PM, level 7
Dr Alex Saffer Montana State University

Email:   alexander.saffer[at]montana.edu

 

Abstract

General Relativity (GR) has been the cornerstone of gravitational physics for a century. Over this time, numerous predictions and tests have strengthened the belief in GR as the foremost theory when discussing gravity. However, GR cannot in its present form be reconciled with either quantum mechanics, or many cosmological observations such as galactic rotation curves or the accelerated expansion of the universe. In an attempt to rectify these shortcomings, modified theories of gravity have been proposed. In this talk, I will present one of these theories and discuss my current work in attempting to test its validity through the development of an exterior spacetime (metric) for a neutron star. From this, we expect to be able to develop a pulse profile which can be used, in conjunction with observations made of the x-ray flux of radiating neutron stars, to place constraints on the theory.


Big Screen Science: The Dish

Sun 7 Oct, 2018 @3.45 PM, Cinema Nova
Dr. Rachael Livermore, DECRA fellow
University of Melbourne

Email: rlivermore[at]unimelb.edu.au


Celebrate space and stars with a fun event for the whole family! Revisit classic sci-fi films on the big screen, followed by fascinating presentation and discussion on how space is depicted in cinema with Astrophysicist Dr Rachael Livermore (The University of Melbourne).

It is a date that will be remembered for all time. July 20 1969 – the day man first set foot upon the moon. That one shining moment was witnessed by a television audience of six hundred million people across the globe. Remarkably, those immortal images came via a “dish” in rural Australia. It may have been one small step for man, but for a handful of Aussie scientists, it was a giant leap. And one that almost didn’t happen… From the creators of the beloved Australian cinema classic The Castle and TV’s Utopia, THE DISH stars Sam Neill, Patrick Warburton, Roy Billing, Kevin Harrington and Tom Long in the incredible true story of Australia’s part in the Apollo 11 moon mission.

For more details and to book your ticket go to: The Dish

Big Screen Science: Dish, The


Astrophysical inference and transient gravitational wave astronomy

Wed 3 October, 2018 @12:00 PM, level 7
Dr Greg Ashton Monash University

Email:  greg.ashton[at]monash.edu

 

Abstract

The LIGO and Virgo detectors offer a new and fascinating window into astrophysics. Already, five binary black hole mergers and one binary neutron star merger have been observed. Bayesian inference has been central to extracting knowledge of these systems. In this talk, I will first give an overview of how inference methods are applied in practise. I will then describe how these inference methods can be used to improve the science that can be done with ground based interferometers: from inferring population distributions to better understanding individual detections. I’ll end by discussing recent efforts by OzGrav to build the next generation of inference tools.


Big Screen Science: Contact

Sun 30 Sep, 2018 @3.30 PM, Cinema Nova
Dr. Rachael Livermore, DECRA fellow
University of Melbourne

Email: rlivermore[at]unimelb.edu.au


Celebrate space and stars with a fun event for the whole family! Revisit classic sci-fi films on the big screen, followed by fascinating presentation and discussion on how space is depicted in cinema with Astrophysicist Dr Rachael Livermore (The University of Melbourne).

More details are here: Contact


The Era of Gravitational Wave Astronomy: GOTO and the challenge of transients

Wed 26 September 2018 @12:00 PM, level 7
Dr Kendall Ackley Monash University

Email:  kendall.ackley[at]monash.edu

 

Abstract

With a single confirmed joint observation of the gravitational waves (GW) emitted from a binary neutron star system with an electromagnetic (EM) counterpart, the era of multimessenger astronomy was born overnight. With only a few detectors online, the poor directional resolution of the GW antennae network leaves hundreds of square degrees to be searched for associated transients. The large number of false-positives which simultaneously litter the sky represent a major challenge to reliably identify and link potential EM counterparts to GW events. In this talk, I will discuss the Gravitational-Wave Optical Transient Observatory (GOTO) which is dedicated to the follow-up of GW event triggers; as well as the ways in which we automatically detect and classify potential astrophysical transients using unsupervised and supervised machine learning algorithms on image-subtracted data. I will also discuss exciting research avenues with routine joint GW-EM observations, such as GW-EM parameter estimation, which may provide further constraints on the Hubble constant independent of the cosmological distance-ladder.


Black Hole Mass Scaling Relations for Spiral Galaxies

Wed 19th September, 2018 @12:00 PM, level 7
Dr Benjamin Davis, Swinburne University

Email:  benjamindavis[at]swin.edu.au

Abstract

For almost a century now, the Hubble-Jeans sequence of galaxies has classified spiral galaxies into morphological classes based on their bulge sizes and the tightness of winding present in their spiral arms. These qualitative morphologies also inform us about the mass of the black hole residing at a spiral galaxy’s centre. Specifically, spiral galaxies that typically possess the largest black holes have large bulges and tightly wound spiral arms. My research focusses on studying spiral galaxy structure and providing accurate, quantitative measurements of their bulge masses and logarithmic spiral arm pitch angles. I will present the details of my recent study of all the known supermassive black holes with directly measured dynamical masses in the literature. For this sample, I have measured their pitch angles and conducted extensive multicomponent decomposition analyses of their surface brightness profiles to determine accurate bulge masses. I will report on the resulting black hole mass scaling relations and discuss their usefulness in predicting unknown black hole masses to generate mass functions and identifying galaxies that might harbour intermediate mass black holes.


Tracing high-z galaxy kinematics from turbulent disks to quenched spheroids

Wed 12th September, 2018 @12:00 PM, level 7
Dr Emily Wisnioski, ANU

Email:  emily.wisnioski[at]anu.edu.au

Abstract

The depth of the KMOS3D Survey has allowed us to study in unprecedented detail rare galaxies at z>1 that are likely in the process of quenching. The short timescales associated with the quenching process make it difficult to catch galaxies “in the act” of shutting down their star formation. Compact star-forming galaxies, making-up ~7% of our sample, are selected to have properties aligned with already quenched galaxies at the same or lower redshifts but forming stars at rates 2-10x higher. We measure resolved kinematics of ~30 of these galaxies within the KMOS3D survey. Our results – the first resolved spectral data of such objects – show that compact star-forming galaxies are rotationally-dominated systems, providing strong evidence that recently quenched galaxies at these epochs are likely to be “fast rotators” . The majority of compact star-forming galaxies show evidence of low molecular gas fractions from ALMA observations and nuclear activity indicative of secular quenching processes that may retain the rotation observed in the star-forming phase. The KMOS3D survey, an integral field survey of over 600 galaxies at z=0.7-2.7 using KMOS at the VLT, will make their data public this year. In addition to the above science (Wisnioski et al. 2018) I will describe the survey and data products that will soon be available to the Australian community.


Are neutron stars turbulent?

Fri 7th September, 2018 @11:00 PM, level 7
Dr Anthony Van Eysden, Montana State University

Email:  anthonyvaneysden[at]montana.edu

Abstract

Instabilities and turbulence in neutron stars have been suggested as the origin of timing irregularities in pulsars such as glitches and timing noise. I will examine the case for turbulence in neutron stars, comparing the conditions in these stars with those in known turbulent astrophysical systems. Particular attention is given to instabilities arising from conditions unique to neutron stars, such as two-stream instabilities driven by the relative rotation between the proton and neutron condensates in the core. We show that magnetic stresses have a stabilizing effect on these instabilities, making them unlikely to be connected with turbulence.


Designing for Discovery in Astronomy’s Data-Intensive Era

Wed 29 August, 2018 @12:00 PM, level 7
Sarah Hegarty, PhD Student
Swinburne University

Email:  shegarty[at]swin.edu.au

Abstract

The dawning era of data-intensive astronomy offers us unprecedented potential for discovery. However, the immense data rates of new-generation telescopes mean that we won’t be able to make these discoveries using established approaches. In this presentation, I will look at how our work practices need to change as we adapt to the data-intensive era – and discuss how we can use what we know about astronomical discovery-making to build more effective workflows. I will present a case study from the field of fast transient science, discussing the development of intelligent workflows for the Deeper, Wider, Faster transient search program, and describing the new eResearch platform PerSieve. I will discuss lessons learned about how astronomers work – and the implications for how we can capitalise on the vast discovery potential of coming data-intensive telescopes.


Constraining asymmetry in Europa’s oceans

Wed 22 August, 2018 @12:00 PM, level 7 Conference Room
Marshall Styczinski, PhD student
University of Washington

Email:  mjstyczi[at]uw.edu

Abstract

Induced magnetic fields from Europa, measured by the Galileo spacecraft, provide the strongest evidence we have for the presence of a salty water ocean beneath the outer ice shell. The observed field is consistent with a global ocean layer with a high dissolved salt content. However, ice layer thickness, ocean depth, and salinity determined from induced magnetic field measurements are dependent on the model applied to represent the interior structure. Past studies attempting to constrain ocean properties have all assumed spherical symmetry, which is not expected for Europa and restricts the validity of the derived constraints. Quantifying the degree of potential asymmetry in the ocean and ice layer is critical to future exploration. Interpretation of magnetic measurements by the upcoming Europa Clipper mission, especially considering plume activity that may have degenerate signals, may be impossible without asymmetric interior models. In this work, we aim to identify constraints on the spatial asymmetry that may be present in Europa’s oceans. Constraints will be determined as extremes in low-order spherical harmonics describing the ice-ocean boundary that are consistent with Galileo gravity and magnetometer measurements and realistic ocean parameters, assuming uniform ocean conductivity. Preliminary results and plans for future work will be presented.
 


Exploring the effects of crystallographic orientation on shock features in Martian meteorites: how does the orientation of a crystal affect how it bends or breaks?

Thurs 16 August, 2018 @14:00 PM, level 6 Opat Room
Dr Lucy Forman, Research Associate
Curtin University

Email:  lucy.forman[at]curtin.edu.au

Abstract

Shock features within Martian samples are thought to result primarily from the impact that launched them from the surface of Mars, and so exploring the material response can help constrain shock parameters, related impact processes and locate candidate launch craters on the Martian surface. Different minerals have varied material responses to stress and, more specifically in this case, the stress applied by a propagating shockwave. Slip systems must be activated in each grain so that the crystal lattice can be deformed. However, often the dominant activated slip system is dependent upon the orientation the stress is applied in, with relation to the crystallographic orientation of the grain, and the physical conditions of the material at the time of impact. Here we explore the effect of crystallographic orientation on the quantifiable amount of crystal deformation that is generated in an impact scenario on the Martian surface.

The initial focus of this study is the lherzolitic Shergottite Roberts Massif (RBT) 04262, which comprises poikilitic pyroxenes amongst a pyroxene and olivine-rich mineralogy. We initially examined a large (10 x 7 mm) twinned pyroxene grain. At the macro scale, shock is heterogeneous but no mineral phase changes have been observed, therefore overall shock is limited. Electron backscatter diffraction (EBSD) techniques were used to determine pyroxene orientation to constrain spectral characteristics and understand the style of deformation within the grains. The data comprise crystallographic information from all mineral phases at a step size of 12.2 µm.

The twinned pyroxene grain is primarily pigeonite based on the composition, and was divided into twins A & B. Twin A shows very little internal deformation in the pigeonite region (<2 º), but a consistently greater amount of misorientation is present in the augite rim. However, twin B, which is twinned on the [001] plane with twin A, shows a variable amount of misorientation throughout the crystal, which appears to undulate in contrast to the radial trend in deformation in twin A.

This sample has a very low porosity, which would have also been true at the time of impact, and therefore heterogeneities in shock are not due to shockwave interactions arising from interaction with pores. We subsequently infer the crystallographic orientation of each grain dictated the degree of crystal-plastic deformation generated by the shock wave. Further EBSD microstructural analysis will be used to constrain the slip systems that have been activated in the pigeonite, and subsequently constrain the physical conditions at the time of impact. This approach may allow determination of the shockwave propagation direction with respect to the plane of the sample. Further Martian samples have been investigated using this analytical approach. This study will contribute directly to our understanding of impact-induced deformation in a suite of rocks ejected from the Martian surface at the same time, and potentially by the same impact event.

 

 


New frontiers in exoplanetary and stellar astrophysics with Australian observational facilities

Wed 08 August, 2018 @12:00 PM, level 7
Associate Professor Rob Wittenmyer, MINERVA Observatory, University of South Queensland

Email:  rob.wittenmyer[at]usq.edu.au

Abstract

Mount Kent Observatory at the University of Southern Queensland is host
to Australia’s newest astronomical research facilities.
MINERVA-Australis is the only Southern hemisphere precise radial
velocity facility wholly dedicated to follow-up of thousands of planets
to be identified by NASA’s Transiting Exoplanet Survey satellite
(TESS). Mass measurements of these planets are critically necessary to
maximise the scientific impact of the TESS mission, to understand the
composition of exoplanets and the transition between rocky and gaseous
worlds. MINERVA-Australis is now operational. I present first-light
results and give an update on the status of the project, which will
ultimately host six 0.7m telescopes feeding a stabilised spectrograph.

The Stellar Observations Network Group (SONG) is establishing a node at
Mount Kent. SONG-Australia will complete the global longitude coverage,
delivering breakthroughs in fundamental understanding of the interiors
of stars for decades to come. SONG-Australia is designed on a “MINERVA”
model, whereby fibres from multiple small telescopes feed a single
high-resolution spectrograph. This approach provides expandability and
reduces cost by using factory-built components that have been
well-tested by the MINERVA teams. As a result of these innovations,
SONG-Australia is expected to be fully operational by late 2019.


Pulsar glitches and vortex tangles: a neutron star super-mixture

Wed 1 August, 2018 @12:00 PM, level 7
Lisa Drummond, PhD Student
University of Melbourne

Email:  l.drummond[at]student.unimelb.edu.au

Abstract

Pulsar glitches are a unique window into the dynamics of neutron matter at extreme densities. Modelling the physical mechanism that produces these glitches is an endeavour that spans many scales: from the quantum mechanical, microscopic interaction of vortices in the superfluid interior to the macroscopic motion of the rigid stellar crust. We can simulate vortex-avalanche-induced glitches by constructing a Gross-Pitaevskii model from first-principles, thereby incorporating the microscopic physics of superfluid vortices (Warszawski, Melatos, 2011; Melatos, Douglass & Simula, 2015). A complementary approach is to model pulsar glitches as a state-dependent Poisson process, thereby capturing the global behaviour of glitching pulsars (Fulgenzi, Melatos & Hughes, 2017). Bridging the stellar and microscopic scales described in these two approaches is an enormous computational and theoretical challenge. These models can each be extended in various ways, for example by including the interaction with the proton superconductor in the core (Drummond & Melatos, 2017). Competition between vortex-vortex repulsion and vortex-flux-tube attraction (pinning) leads to “glassy” behaviour characterized by multiple metastable states spaced closely in energy. Vortex tangles emerge as a consequence of the frustration in the system. The tangles evolve in a complicated fashion when driven out of equilibrium and a three-dimensional investigation reveals new vortex behaviours for misaligned magnetic and rotation axes.


Pulsars as gravitational wave sources

Wed 25 July, 2018 @12:00 PM, level 7
Dr Matthew Pitkin, Post-doctoral Research Fellow
University of Glasgow

Email:  matthew.pitkin[at]glasgow.ac.uk

Abstract

Transient sources of gravitational waves, such as coalescing black holes and neutron stars, have obviously been at the forefront of gravitational wave astronomy. But, there are still many intriguing sources that have yet to be detected, and these include continuous quasi-monochromatic signals from individual rapidly-rotating neutron stars. Known pulsars therefore are intriguing targets for searches for such signals. In this talk I will give an overview of searches for gravitational waves from pulsars using the LIGO and Virgo detectors. I will describe some recent work that may provide some evidence that millisecond pulsars have a minimum ellipticity, which makes detection of these sources more plausible with future gravitational detectors. I will also describe how hierarchical Bayesian inference can potentially be used to detect signals from an ensemble of pulsars and infer the distribution of pulsar ellipticities.


Titans of the Early Universe: The origin of the most massive, high-redshift quasars

Wed 18 July, 2018 @12:00 PM, level 7
Dr. Tyrone Woods, Post-doctoral Research Fellow
Monash University

Email:  tyrone.woods[at]monash.edu

Abstract

The discovery of billion solar mass quasars at redshifts of 6-7 challenges our understanding of the early Universe; how did such massive objects form in the first billion years? Observational constraints and numerical simulations increasingly favour the “direct collapse” scenario. In this case, an atomically-cooled halo of primordial composition accretes rapidly onto a single protostellar core, ultimately collapsing through the Chandrasekhar-Feynman instability to produce a supermassive (~100,000 solar mass) “seed” black hole. In this talk, I’ll present a systematic study of the lives and deaths of these objects, using the 1D implicit hydrodynamics and stellar evolution code KEPLER. We include post-Newtonian corrections to gravity and a detailed treatment of nuclear burning processes using an adaptive network. We find a simple relation between the infall rate and the final mass at collapse, and rule out the existence of rapidly-rotating supermassive stars. I’ll also discuss the possibility of early chemical enrichment from these objects, observational prospects in the era of the JWST, and briefly summarize other future directions agreed upon at our workshop “Titans of the Early Universe” held at the Monash Prato Centre in Italy, in November of last year.


Detectability of 21cm signal during the Epoch of Reionization with 21cm-LAE cross correlation

Wed 11 July, 2018 @12:00 PM, level 7
Shintaro Yoshiura,
Kumamoto University

Email:  161d9002[at]st.kumamoto-u.ac.jp

Abstract

The 21cm signal is a powerful tool to probe the Epoch of Reionization. However the detection of the redshifted 21cm signal is difficult due to the bright foregrounds. For mitigating the foreground contamination, the cross correlation with other observable is useful. Here, we predict the detectability of the cross power spectrum between 21cm signal and Lyman-alpha emitter (LAE) by using numerical reionization simulation and assuming ongoing and future observations. For 21cm observation, we assume radio survey by the Murchison Widefield Array (MWA) and Square Kilometre Array (SKA). The LAEs are detected at z=5.7, 6.6 and 7.3 by Subaru Hyper Suprime-Cam (HSC).  In this work, we find that the MWA can detect the signal by combining the spectroscopic survey with the Prime Focus Spectrograph (PFS). In practice, however, the error of cross power spectrum is dominated by the foregrounds, and moderate foreground removal is required.  


Science vs Cinema: Star Trek II – Wrath of Khan

Sun 8 Jul, 2018 @3.30 PM, NOVA cinema
Dr. Rachael Livermore, DECRA fellow
University of Melbourne

Email: rlivermore[at]unimelb.edu.au


Celebrate space and stars with a fun event for the whole family! Revisit classic sci-fi films on the big screen, followed by fascinating presentation and discussion on how space is depicted in cinema with Astrophysicist Dr Rachael Livermore (The University of Melbourne).

More details are here: Star Trek II – Wrath of Khan


The most powerful radio-sources in the southern hemisphere

Mon 2 July, 2018 @12:00 PM, level 7
Dr. Sarah White, Research Associate
Curtin University

Email:  Sarah.White1[at]curtin.edu.au

Abstract

Powerful radio-galaxies feature heavily in our understanding of galaxy evolution. However, when it comes to studying their properties as a function of redshift and/or environment, the most-detailed studies tend to be limited by small-number statistics. In this talk, I will present a new sample of nearly 2,000 of the brightest radio-sources in the southern hemisphere (Dec. < 30 deg). These were observed at low radio-frequencies as part of the GaLactic and Extragalactic All-sky MWA (GLEAM) survey, conducted using the Murchison Widefield Array (MWA). Being brighter than 4 Jy at 151 MHz, we refer to these objects as “The GLEAM 4-Jy Sample”. Thanks to the location of the MWA in a protected, radio-quiet zone, we have excellent spectral coverage for these sources, with 20 radio flux-densities spanning a frequency range of 72-231 MHz. A key component of this project is identifying the appropriate host galaxy of the radio emission, with these positions feeding into target lists for the Taipan Galaxy Survey. Having 10 times as many sources as the most-prominent, low-frequency radio-source sample that is optically complete (the revised Third Cambridge Catalogue of Radio Sources; 3CRR), the GLEAM 4-Jy Sample will allow models of powerful active galactic nuclei to be tested more robustly.


Number of posts found: 80