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
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
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
Dr Adriano Poci
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
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.
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.