2018 Abstracts

2018 Abstracts

Dr Christoph Bergmann

Title: Exoplanetary Science with Veloce at the AAT

Abstract: Australia’s newest planet hunting facility, Veloce, has commenced operations in September 2018. Veloce is a high-resolution ├ęchelle spectrograph installed at the 3.9-m Anglo-Australian Telescope at Siding Spring Observatory. With a Menlo Systems laser frequency comb for simultaneous wavelength calibration, a wavelength coverage from about 590 to 950 nm, a focal plane segmenting IFU, and a temperature and pressure stabilised design, Veloce Rosso will provide sub-m/s radial-velocity precision and will thus enable a new level of Doppler exoplanet science in Australia.

Amongst our principal science goals are the follow-up of potentially habitable exoplanets discovered by NASA’s TESS satellite, the search for solar system analogues around the most stable stars, and the search for habitable zone planets, especially around faint low-mass M-dwarfs. However, Veloce can also be used as a general-purpose instrument for high-resolution spectroscopic observations, eg for asteroseismology or abundance analysis.
After giving an overview of the instrument’s design and capabilities, and the plans for its science exploitation, I will discuss some aspects of the approach to the data reduction process in the light of what is required to obtain sub-m/s radial velocity precision. Finally, I will present some first results from our commissioning runs.

Mr Theodoros Anagnos

Title: Ways to maximising the impact of a presentation

Abstract: Presentations are everywhere, from industry to academia. To know how to present and spread the knowledge if free of charge and possibly a nice way to gain more new ideas and collaborations. Many people in academia are working on promising projects and publish wonderful results, though when they try to present them live in the audience they luck of high presenting skills that lead to create confusion.This presentation is a collection of many tricky points to pay attention as well as many methods for maximising the impact of a presentation, targeting to be understandable from the audience. Most of this presentation is by Dr. Tom Herbst from MPIA in Heidelberg who constructively impact many people's presentation skills including further techniques from personal experience.

Dr Gioia Rau

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

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.


Prof. Andrew Hopkins

Title: Measuring the stellar initial mass function

Abstract: The birth of stars and the formation of galaxies are cornerstones of modern astrophysics. While much is known about how galaxies globally and their stars individually form and evolve, one fundamental property that affects both remains elusive. This is problematic because this key property, the stellar initial mass function (IMF), is a key tracer of the physics of star formation that underpins almost all of the unknowns in galaxy and stellar evolution. It is perhaps the greatest source of systematic uncertainty in star and galaxy evolution. The past decade has seen a growing number and variety of methods for measuring or inferring the shape of the IMF, along with progressively more detailed simulations, paralleled by refinements in the way the concept of the IMF is applied or conceptualised on different physical scales. This range of approaches and evolving definitions of the quantity being measured has in turn led to conflicting conclusions regarding whether or not the IMF is universal. Here I summarise the growing wealth of approaches to our understanding of this fundamental property that defines so much of astrophysics, and highlight the importance of considering potential IMF variations, reinforcing the need for measurements to quantify their scope and uncertainties carefully. I present a new framework to aid the discussion of the IMF and promote clarity in the further development of this fundamental field.


Dr Pamela Gay

Title: Science through Citizen Science: navigating the landscape of public engagement

Abstract: Since the first days of variable star astronomy, astronomers have turned to dedicated volunteers to help them accomplish science tasks they otherwise couldn’t complete. From providing time coverage from night to night, to providing global coverage as the world turns. These amateur astronomers went to great ends to make meaningful contributions to research. In these “mail in your data” dats, it was clear that consent was given for data to be used, and programs like the AAVSO and MPC had guidelines on how data would be submitted by observers and used by scientists. Today, online technologies have created a Wild West of Citizen science programs and platforms that span observational and online activities that may or may not eventually contribute to research. In this talk, the promise of citizen science will be weighed against the issues of data quality and data privacy, and the necessity of engaging with a community. The possibilities of combining citizen science data and machine learning to accelerate science will also be addressed. The talk will close with a discussion of how your science may be able to leverage the CosmoQuest citizen science platform.


Mr Adam Joyce

Title: Pocket Astronomy in Pocket-Sized Towns: National Science Week Outreach Roadtrip 2018

Presenter: Mr Adam Joyce, Senior Scientific Officer, Department of Physics and Astronomy, Macquarie University

Abstract: Undergraduate students from the Department of Physics and Astronomy along with staff members traveled to regional NSW towns, Wee Waa, Werris Creek, Baraba and Dorrigo to deliver a Planetarium Show, Solar Telescope Viewing, A Talk from Professor Mark Wardle about the Black Hole at the centre of the Milky Way and a presentation on the Dark Sky Project, followed by an evening telescope viewing session.

The Association for Astronomy, which is part of the Department of Physics and Astronomy, have done similar things in the past. This project will see the group visit 4 towns in 4 days, and present with a view to discuss Australian Science, namely Astronomy, with towns that have not the facilities or the service to engage with Astronomy outreach, and engage with the local community about Dark Skies.

We also gifting a telescope to each town we visit, and provided a short training session on the equipment.

I will be giving a summary of the Roadtrip with the hope that it will inspire others to do similar activities in the future.


Dr Anshu Gupta

Title: Chemical evolution of star-forming galaxies in cluster environment

Abstract: As the largest gravitationally bound systems in the Universe, galaxy clusters are a unique laboratory for studying the extremes of galaxy evolution. Large-scale cluster potential has been known to play a significant role in the morphological and colour transformation of galaxies. I use chemical abundance to tracer the cumulative effect of various baryonic processes affecting galaxy evolution in a galaxy cluster. Using observations with DEIMOS/Keck, I find a cluster-scale gradient in the metallicity of star-forming galaxies and present it as a new angle to identify physical processes driving the chemical enrichment of cluster galaxies. In this talk, I will present my work with IllustrisTNG simulations, where we find a systematic signature of ``chemical pre-processing'' of infalling galaxies. I will show that the inflow of enriched gas (pre-enrichment) plays a significant role in driving the chemical evolution in the overdense environment in illustrisTNG simulations.


Dr Mireia Montes

Title: Exploring the fossil record of cluster assembly: the intracluster light

Abstract: An enigmatic component present in galaxy clusters is the intracluster light (ICL), made up of stars that are not bound to any particular galaxy but drift freely between galaxies in the cluster. Thought to form by the stripping of satellite galaxies as they fall into the cluster, characterizing the ICL is key to understand the assembly mechanisms occurring inside galaxy clusters. Despite its importance, little is known about this light as it is very difficult to observe due to its low surface brightness. In this sense, multi-wavelength deep observations provide valuable information about the origin of this light.

In this talk, I will present the latest advances in the understanding of the ICL. Using multi-wavelength observations provided by the Hubble Frontier Fields, we have analyzed the ICL of 6 clusters at z~0.4, an interesting time to explore as numerical simulations predict that the ICL forms at z<1. Our results suggest that the ICL of these massive (> 10^15 Msol) clusters is formed by the stripping of MW-like objects that have been accreted at z<1, in agreement with current simulations. Furthermore, we have found that the ICL follows the shape of its underlying dark matter halo, in agreement with the idea that this light is the result of the hierarchical assembly of the galaxy cluster.

Ms. Fiona Panther

Title: Antimatter in the Milky Way: a theoretical perspective

Abstract: For more than 50 years, the rate and distribution of positron (anti-electron) annihilation in the Milky Way has puzzled astronomers. Positrons with low (~MeV) initial energies are predominantly produced by beta+ unstable radioactive elements, however, the observed rate of positron annihilation in the Milky Way far exceeds the predicted rate of positron production by ‘conventional sources’ such as core-collapse and Type Ia supernovae.  Moreover, the observed distribution of positron annihilation in the Milky Way appears to trace the older stellar populations of the Galaxy (the Galactic bulge and a thick, truncated disk), while radioactive material is predominantly synthesised in the thin disk of the Galaxy. Over the past few years, we have constrained scenarios for positron injection and transport in energetic outflows of the Milky Way, investigated positron annihilation sites in the Milky Way beyond annihilation with electrons bound to hydrogen and helium atoms, as well as investigating in detail the possibility that positrons are born in the ejecta of subluminous thermonuclear supernovae that concentrate in old stellar populations. I will present highlights of this theoretically-focussed work in my talk, along with emphasis on the implications of this work beyond high-energy astrophysics, including how MeV astronomy is a vital probe of nucleosynthesis, galactic chemical evolution and galactic dynamics.


Ms. Kirsten Banks

Title: Emus can’t fly, but there’s an Emu in the sky

Abstract: Aboriginal and Torres Strait Islander people of Australia have been looking up into the skies for tens of thousands of years. Come on a journey of a different perspective of the night sky with proud Aboriginal Astronomer and Science Communicator Kirsten Banks as she leads you through star stories and the science within them. Discover why Emus can’t fly, despite there being an Emu in the sky!


Dr Guillermo Blanc

Title: "Next Generation IFU Surveys of Nearby Galaxies: Resolving the Physics that Drive Galaxy Evolution"

Abstract: Galaxies form and evolve via physical processes that operate over a large dynamic range of spatial scales, from the tens of kpc scales of galactic disks down to the sub-pc scales in which stars form within GMCs. Optical integral-field spectroscopy, especially when combined with IR, sub-mm, and radio datasets, offers a powerful tool to study the physics of star formation, feedback injection, chemical enrichment, and galactic dynamics within galaxies, but comprehensive surveys of nearby galaxies have been limited by their ~500 pc -1 kpc spatial resolution. At such coarse resolution individual sites of star formation, metal production and feedback injection cannot be resolved. In this talk I will present early results from the "Physics at High Angular Resolution in Nearby Galaxies" (PHANGS) survey, a combination of two ESO and ALMA Large Programs aimed at mapping the ionized and molecular ISM and stellar content of all massive star forming galaxies in the Local Volume (D<17 Mpc) at <100 pc resolution. I will also discuss the Local Volume Mapper (LVM) project, one of the programs to be executed as part of the Sloan Digital Sky Survey V (SDSS-V). The LVM will start operating in 2020, and will produce optical IFU data-cubes of the bulk of the Milky Way disk, the Magellanic Clouds, M31, and M33, and dozens of Local Group dwarfs, with spatial resolutions ranging from 0.1 pc to 20 pc, resolving the scales in which stars form and feedback and metals are injected into the ISM.


Dr Boud Boukema

Title: Hypothesis: dark energy is recent negative average spatial curvature

Abstract: The standard model of cosmology, the LambdaCDM (LCDM) model, is based on a shortcut rather than a full application of the Einstein equation to the observed Universe. Several cosmologists working towards more realistic cosmological models, within the context of standard general relativity (the Einstein equation), find that the emergence of negative average spatial curvature over the past 5 to 10 billion years, as a result of the main epoch of formation of the cosmic web of filaments of galaxies, clusters of galaxies, and voids, provides a numerically and observationally realistic dark-energy-free model of the Universe. Separating the LCDM model from relativistic-structure-formation models of the Universe will be one of the challenges for 4MOST and other upcoming deep wide galaxy surveys.


Dr Ettore Carretti

Title: The S-band Polarisation All Sky Survey (S-PASS): a new view of the radio polarised sky.

Abstract: The S-band Polarisation All Sky Survey (S-PASS) has imaged the polarised emission of the southern sky at 2.3 GHz with the Parkes Radio Telescope. Aimed at overcoming the depolarisation issues of previous surveys taken at lower frequencies, S-PASS has unveiled diffuse polarised emission down to the Galactic disc, revealing new and unexpected large scale structures. The science covered by S-PASS is diverse ranging from the Milky Way to cosmology. The discovery of the Milky Way Lobes counterparts of the gamma-ray Fermi Bubbles, study of the Galactic ISM turbulence, investigation of the dynamics of galaxy clusters, and the study of CMB foregrounds are just a few examples. In this talk we will present the survey, the technical challenges addressed to realise it, the results obtained so far and the work in progress.


Prof Licai Deng

Title: Site study in Tibet-Qinghai Plateau for future astronomy in China

Abstract: China has a large span in longitude, missing good observing site for astronomy has been a bottle neck for not only the development of astronomy in the country, but also for ground base observations, especially in time-domain, in a global perspective. China has the desire to build modern infrastructure for fundamental research, including large optical-IR telescopes, in the coming decade. None of the current sites will be suitable for such facilities. A precursor survey of good sites in west China shows that the most promising candidate sites may exist on the plateau. In this talk, I am going to report the results of the site surveys and will concentrate mostly on the sites in northern part of the plateau. I will also give a short introduction of our institute NAOC.


Dr Jeffrey Simpson

Title: The GALAH survey: Co-orbiting stars and chemical tagging

Abstract: This is a study using the second data release of the GALAH survey of stellar parameters and elemental abundances of 15 pairs of stars identified as potentially co-moving pairs using proper motions and parallaxes from Gaia DR1. We find that nine very wide (>1.7 pc) pairs of stars do in fact have similar Galactic orbits, while a further six claimed co-moving pairs are not truly co-orbiting. Six of the nine co-orbiting pairs have reliable stellar parameters and abundances, and we find that three of them are quite similar in their abundance patterns, while three have significant [Fe/H] differences.


Prof Geoffrey Clayton

Title: Is the Earth Flat?

Abstract: You may ask why I am asking a question with such an obvious answer, but a few minutes on Google will demonstrate that the Flat Earth Society is still going strong. Rappers, professional athletes, and lots of youtube videos argue that the Earth is indeed Flat. This is the ultimate Conspiracy Theory, and in the post-truth era the Flat Earth is doing very well. It is very important for us as scientists, during classes and outreach activities, to meet this conspiracy theory head-on and be able to give clear explanations showing that, yes, the Earth is round. Come to this talk with your favourite proof that the Earth is Round. I will give a few examples of my own.


Ms Anke Arentsen

Title: Extremely metal-poor (carbon-enhanced) stars as probes of the Early Universe

Abstract: Our Milky Way still hosts remnants from the era of first star formation in the form of extremely metal-poor stars, which we can study in detail. The chemical compositions of these stars give indirect insight into the properties of the very first generation of stars. In the first part of my talk I will discuss recent results of the Pristine survey, which is a photometric survey aiming to significantly extend the number of known extremely metal-poor stars in our Galaxy. In this talk I will focus mainly on the Galactic Bulge program within the Pristine survey. In the second part of my talk I will focus on a sub-class of extremely metal-poor stars, the carbon-enhanced metal-poor (CEMP) stars. The fraction of stars enhanced in carbon increases dramatically at the lowest metallicities, and these CEMP stars can place additional constraints on the properties of the first generation of stars. I will discuss recent findings from our radial velocity monitoring program of CEMP-no stars, where we have found an interesting relation between the binarity of these stars and their absolute carbon abundance.


Dr Chris Gordon

Title: "Is the Galactic Bulge Shining in Gamma Rays?"

Abstract: "Data from the Fermi Large Area Telescope indicates that there is an extended source of GeV gamma-ray photons coming from the Galactic Centre. Initially, it was thought that this could be due to self-annihilating dark matter. However, recent work shows that the spatial morphology better matches the shape of the Galactic bulge rather than a spherically symmetric shape that would be expected from a dark matter signal. I will discuss this result and also give details on the evidence that the source of the excess is due to an unresolved population of millisecond pulsars."


Dr. Farhad Yusef-Zadeh

Title: The Interaction of Cosmic Rays with Molecular Clouds in the Galactic Center

Abstract: The ISM in the inner few hundred pc of the Galactic center differs from elsewhere in the Galaxy. This region is centered on a 4 million supermassive black hole and is occupied by a large concentration of molecular gas with high column density, high velocity dispersion and high gas temperature. Recent IR and X-ray observations indicate that the cosmic ray ionization rate is higher than elsewhere in the Galaxy by one to two orders of magnitudes.

The interaction of an enhanced cosmic-ray flux with molecular clouds in this region explains a number of observations: i) the ubiquitous warm molecular gas observed throughout the Galactic center, ii) the power law spectrum of GeV emission, iii) FeI Kalpha emission at 6.4 keV and iv) the unusual chemistry of molecular gas, as probed by a number of molecular tracers. In this picture, relativistic bremsstrahlung radiation explains the origin of diffuse gamma-ray and 6.4 keV line emission from the Galactic center region.


Dr Andrew Lehmann

Title: High velocity shock waves in extragalactic turbulent cold gas

Abstract: The formation and evolution of galaxies is determined by the processes regulating the conversion of cold molecular gas into stars. In this talk I summarise the MIST project (Molecules, magnetic fields and Intermittence in coSmic Turbulence) , a european effort to study these processes inspired by surprising ALMA observations of CH+ emission and absorption in a sample of high-z starburst galaxies. I will also outline my place in the project which includes extending the Paris-Durham public code, a state-of-the-art magnetised shock model, to higher velocities (>30 km/s). This will allow us to more accurately predict the molecular emission from the distribution of shocks expected to be present in turbulent reservoirs  of cold gas.


Dr Gayandhi De Silva

Title: Galactic Archaeology with HERMES: open clusters and stellar streams.

Abstract: The GALAH survey is a pioneering survey that is exploring the motions and detailed chemical compositions of 1 million stars in the Milky Way. Closely related to this is the HERMES Open cluster program, collecting uniform high resolution, high signal to noise data for open clusters spanning a large range in age, metallicity and distance. In this presentation I will give an overview of the developments in Galactic Archaeology, the current status and results with a snap shot of science from these surveys.


Dr Valentina Baccetti

Title: Information loss paradox and the effects of black hole radiation.

Abstract: Event horizons are the defining feature of classical black holes. They are the key ingredient of the information loss paradox which, as paradoxes in quantum foundations, is built on a combination of predictions of quantum theory and counterfactual classical features. Within the semi-classical theory we investigate the possibility that black hole radiation still does not allow for a finite time crossing of the Schwarzschild radius of collapsing matter as seen by distant observers. The exact form of the pre-Hawking radiation is not yet settled, and we make only minimal assumptions about its nature.


Dr Yang Huang

Title: The LAMOST Galactic Spectroscopic Surveys

Abstract: One of the fundamental tasks of modern astrophysics is to understand how galaxies form and evolve. Generally, the quest can be pursed in two ways: statistical analyses of large samples of distant galaxies (deep-field cosmology) and detailed studies of large samples of member stars in the Local Group of galaxies including our own, the Milky Way (near-field cosmology). Initiated and aimed to make a major contribution to this latter, ‘near-field cosmology’ quest for understanding the galaxy formation and evolution, the LAMOST Galactic Spectroscopic Surveys have hitherto collected quality spectra of over 7M Galactic stars, and this number is still increasing at a rate of 1M per annum. Combining with data from other available photometric, astrometric and spectroscopic surveys (e.g. Gaia, APOGEE, GALAH), the Surveys have yielded a unique dataset to help us draw an exquisite picture of unprecedented detail of our Galaxy, in particular of the Galactic disk. In this talk, I will present the scope and motivation, data reduction and release, as well as scientific results of the surveys.


Dr Simon Murphy

Title: An exciting haul of planetary, binary and triple systems from pulsation timing
Abstract: The orbital parameters of binary stars at intermediate periods (100-1000 d) are difficult to measure with conventional methods and are very incomplete. For the past couple of years I’ve been developing a method that uses stellar pulsations to determine the orbital parameters of binary stars, which is particularly suited to intermediate periods and can detect objects down to planetary masses. It has tripled the number of intermediate-mass stars with fully solved binary orbits. The detected companions include planets, brown dwarfs, and main sequence stars with masses between 0.1 and 2.5 Msun; over 20% are white dwarfs in blue straggler systems, and a few companions could be neutron stars or black holes. Some systems are clear triples, and many will become Type Ia supernovae and related phenomena. Statistically robust mass-ratio and eccentricity distributions will be presented, and I will explain what they tell us about binary star formation.

Dr Adriano Poci

Title: The Chemical and Dynamical Composition of NGC 3115
Abstract: The formation history of a galaxy is the integration of all dynamical and chemical processes over its lifetime. Typically, models of galactic dynamics and stellar populations are considered independently from one another, while in reality they are intimately connected facets of galaxy formation.
We exploit remarkable new spatially-resolved data from the MUSE integral-field unit to conduct a combined dynamics/stellar-populations analysis of the nearby S0 galaxy NGC3115, in order to infer its true formation history. I will present the detailed models that go into this analysis - namely the fully general, triaxial Schwarzschild orbit-based dynamical models, and full-spectral-fitting star-formation histories, as well as how we combine these two concepts to uncover the assembly history of this galaxy.

Dr Christopher Usher

Title: Using Globular Cluster Stellar Populations to Understand Galaxy Formation
Abstract: Globular clusters are important tools to help us understand how galaxies form and evolve. Globular cluster formation tells us about the conditions of extreme star formation while their survival from high redshift tell us about the processes of galaxy assembly. Being much brighter than red giant stars, globular clusters allow the stellar populations of galaxies to be studied at much greater distances. Thus a wider range of galaxy masses, environments and morphologies to be studied than can be with resolved stars. Using data from the WAGGS survey of massive star clusters in the Milky Way and its satellite galaxies and the SLUGGS survey of the globular cluster systems of massive early-type galaixes, I will talk about how we can measure the metallicities of globular clusters using the strength of the calcium triplet in integrated light. Using globular cluster metallicity distributions and the relationships between globular cluster colour and metallicity, I will present evidence that different galaxies with similar masses experienced different formation histories. I will compare these observations with the predictions of the E-MOSAICS cosmological simulations of the formation of globular cluster systems. I will also talk about how the E-MOSAICS simulations have allowed to us to understand how globular cluster colour distributions vary with globular cluster luminosity (the 'blue tilt').

Dr Chris Tout

Title: Highly Magnetic White Dwarfs and other Stars
Abstract: White dwarfs with surface magnetic fields in excess of 1MG are found as isolated single stars and relatively more often in magnetic cataclysmic variables.  Some 1,253 white dwarfs with a detached low-mass main-sequence companion are identified in the Sloan Digital Sky Survey but none of these is observed to show evidence for Zeeman splitting of hydrogen lines associated with a magnetic field in excess of 1MG.  If such high magnetic fields on white dwarfs result from the isolated evolution of a single star then there should be the same fraction of high field white dwarfs among this SDSS binary sample as among single stars.  Thus we deduce that the origin of such high magnetic fields must be intimately tied to the formation of cataclysmic variables.  The formation of a CV must involve orbital shrinkage from giant star to main-sequence star dimensions.  It is believed that this shrinkage occurs as the low-mass companion and the white dwarf spiral together inside a common envelope.  CVs emerge as very close but detached binary stars that are then brought together by magnetic braking or gravitational radiation.  We propose that the smaller the orbital separation at the end of the common envelope phase, the stronger the magnetic field and investigate simple dynamo models for which this is a natural outcome.


Jielai Zhang

Title: Exploring the low surface brightness Universe with the Dragonfly Telephoto Array
Abstract: The low surface brightness Universe is largely unexplored. The limiting factors for low surface brightness observations are not photon statistics or image resolution, instead they are systematic factors such as a telescope s internal reflections, sky subtraction, flat fielding and the wide-angle point-spread-function. The Dragonfly Telephoto Array addresses these factors by a combination of hardware and software. The telescope consists of 48 commercial Canon telephoto lenses, and is able to see low surface brightness structures about 10 times fainter than previously possible with its 2.4 x 3.2 degree wide field of view. I will describe the technology behind Dragonfly, and how I and my team have used it to discover enormous stellar disks, properties of interstellar dust and ultra-diffuse-galaxies.


Dr Stuart Ryder

Title: Binary companions to stripped-envelope supernovae
Abstract: The classes of Type, Ib, and Ic core-collapse supernovae appear to represent progressively greater stripping of the progenitor star's outer envelope prior to explosion, but it is unclear how much of this stripping is due to stellar winds and mass-loss, or to interaction with a massive binary companion. We have used the Hubble Space Telescope to search for surviving binary companions to nearby stripped-envelope supernovae in the ultraviolet. I will describe our results for the broad-lined Type Ic SN 2002ap, and for the Type IIb SN 2001ig.


Dr Rubina Kotak

Title: Faint and fast, bright and long-lived transient: what are they telling us?
Abstract: One of the main challenges of current supernova research is to identify the nature of stars that explode, and to link this knowledge to observed supernova properties. Nowhere is this problem more urgent than the most massive stars in the local and the distant Universe. Recent exciting results have challenged currently accepted paradigms of stellar evolution, and for these supernovae, ever more exotic scenarios are being proposed. I will discuss a few special cases with the currently-accepted framework that highlight gaps in our knowledge.


Dr Themiya Nanayakkara

Title: Hunting for the first star I: Attempts to demystify He II with MUSE
Abstract: In the request for identifying pop-III stars, the most sought-after emission line is He II, however, stellar population models are unable to accurately predict the He II features while being consistent with other emission line diagnostics. To produce He II ionizing photons, stellar populations require sources of heard ionizing radiation with energies >= 54.4 eV and sources as AGN, shocks, X-Ray binaries, stellar rotation and /or binary stellar evolution, and post-AGB stars have been suggested as possible contributors.  To accurately identify relative contributions from these with wide variety of sources, high signal-to-noise spectra with rest-frame UV/optical coverage and advanced stellar population/photoionization models are required.

The VLT/MUSE GTO program has obtained deep 10-30h exposures of Hubble legacy fields yielding rest-UV spectra of galaxies at z≈2-6. In this talk I will represent recent results of the MUSE program and compare the z≈2-4 He II emitters with expectations from photoionization modelling to explore their stellar population and ISM conditions. I will address the necessity to obtain high signal-to-noise spectra of individual galaxies to model rest UV emission and absorption systems along with auxiliary rest-NIR lines to constrain stellar population properties of galaxies at high-z, which will be aided by combined studies by MUSE and JWST in future. I will further briefly discuss the prospects of observing population IIII systems in the early universe.

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