School of Physics Colloquia 2011
21 February
A./Prof. Mary E. Putman (Columbia University)
Feeding galaxies baryons
Abstract:
The methods in which gaseous baryons get into galaxies to form stars remain uncertain, though for a galaxy like the Milky Way it is thought to be a somewhat continuous process. I will discuss this process in the context of predictions from simulations and the tests provided by observations. Gas in a halo above the star forming disk of galaxies is a common feature and the properties of this gas and at the disk-halo interface provide insight into gas accretion. I will also discuss a population of newly discovered cold clouds that potentially represent a combination of cooling disk gas, new dwarf galaxies, and stellar feedback.
28 February
Prof. Manfred Simon (University of Siegen)
The PAMELA experiment: A space mission on cosmic rays, antimatter, and dark matter
Abstract:
Pamela is a space mission which is designed to measure energetic cosmic ray particles and antiparticles from space over a large energy regime, from 100 MeV to almost 1 TeV. It was put into orbit on June 15th, 2006, and has been transmitting scientific data continuously since that time.
The main components of the instrument are a magnetic spectrometer, with a permanent magnet, a time of flight system and an imaging calorimeter. These detectors in combination provide a high level of particle identification. The instrument precisely measures the charge, the charge-sign and the energy of the incoming particles. As well as measuring antiprotons and positrons in an unexplored energy regime and with unprecedented statistical precision, Pamela will improve our understanding of cosmic rays in many aspects. This applies to galactic cosmic ray particles as well as to solar particles.
The talk will present the scientific objectives of Pamela, explain the instrument, and then focus on published results (positron, antiproton, electron, proton and helium spectra) with emphasis on their impact on the discussion about the nature of Dark Matter.
7 March
Prof. Iver Cairns and Drs Seb Juraszek, Tony Monger, George Shan, and Sue Yang (University of Sydney)
IT facilities and support in the School of Physics
Abstract:
This colloquium will overview the School's IT environment, emphasizing the network, workstation, software, and advanced computing facilities and support available to users. The primary goals are to inform new staff and students about the facilities and support available and to describe to existing users the changes and upgrades made over the last year. Presentations will be made by Sebastian Juraszek (Unix and Linux computers, network, and software), Tony Monger (Macintosh computers etc., ordering, infrastructure, network design, and teaching labs), George Shan (Windows computers, network, and software), Sue Yang (high-level scientific computing, software, and support), and Iver Cairns (policy and context; academic in charge of IT). They will also provide details of where to find IT information on the School's web pages and how to request IT support.
14 March
Dr Mikhail Lapine (ANU / University of Seville)
Nonlinear and tunable metamaterials
Abstract:
Metamaterials have been a hot research topic for the last decade, bridging theoretical and applied electrodynamics, electrical engineering, and material science, while holding out the promise of valuable applications. In this talk, we will first discuss how artificial magnetism is built up within metamaterials. One of the key aims for artificial magnetics is to achieve negative permeability (preferably in a wide frequency range), in order to develop applications based on negative refraction. We will analyse how the properties of magnetic metamaterials can be reliably modelled, and which parameters control permeability resonance. Next, we will address more recent developments based on the structural flexibility of metamaterials. We will see how efficient structural tuning can be achieved, discuss near-field effects in mutual interaction between metamaterial elements, and show how to give metamaterials a nonlinear response. We will see that nonlinear magnetic properties can be achieved through electrically nonlinear components, yielding a high efficiency for nonlinear processes; this also opens a path to tunable metamaterials. Finally, we will get acquainted with a novel proposal to design nonlinear metamaterials, which is based on the structural degree of freedom and emerges in a self-coupled linear system. We will discuss the curious patterns of nonlinearity and bi-stability, expected to be observed in artificial magneto-elastic structures.
21 March
Prof. Allan Clark (University of Geneva)
Status of the Large Hadron Collider and the ATLAS Experiment at CERN
Abstract:
I will give an overview of the status and prospects of the Large Hadron Collider (LHC) at CERN, and of the ATLAS experiment where both the University of Sydney and the University of Geneva are collaborators. A selection of the most recent results from ATLAS will be presented, as well as a glimpse of what might be expected in the near future. I will also give a short introduction describing the activities of the Faculty of Science and the School of Physics at the University of Geneva.
28 March
A./Prof. Reza Hashemi-Nezhad (University of Sydney)
A fast track towards an industrial-scale Accelerator Driven System
Abstract:
An Accelerator Driven System (ADS) is a sub-critical nuclear assembly that is coupled to a high-power ion accelerator. It has been proven that an ADS can provide safe nuclear energy in which the possibility of a Chernobyl-type accident is zero. These systems can breed their own fuel from thorium, an abundantly available element, and can incinerate their own nuclear waste.
The main obstacles in the way of an industrial-scale ADS are:
- construction of an ion accelerator with a power greater than 10 MW;
- finding a solution for radiation damage to the structure of the ADS — especially the accelerator beam window — induced by energetic nuclear particles; and
- cooling of the target, in which a power of more than 10 MW is continuously dumped in a volume
equivalent to that of a rugby ball.
We propose a method that reduces the effects of these obstacles by a factor of about three, and smoothes the way towards an industrial-scale ADS.
4 April
Dr Rob Sharp (Australian National University)
GMTIFS: The Giant Magellan Telescope Integral Field Spectrograph
Abstract:
The Giant Magellan telescope (GMT) project is a program to build the next generation of astronomical telescope at the Las Campanas Observatory in the Chilean Andes. As a partner in the GMT consortium, our group at the ANU is near completion of the design study for a proposed near-infrared integral field spectrograph, GMTIFS. GMTIFS will capitalize on the intrinsic light gathering power of a 22 meter telescope and the diffraction limit of the 25 meter effective aperture diameter to deliver unprecidented resolution observations of astronomical sources, both spectrally and spatially. I will give a brief overview of GMT and an introduction to the relatively new field of integral field spectroscopy before presenting a number of the science cases driving the development of GMTIFS.
11 April
Prof. Iver Cairns (University of Sydney; National Committee for Space Science)
Australia's new Decadal Plan for Space Science: Summary and implications for the University of Sydney
Abstract:
Australia was the fourth nation to launch a spacecraft into orbit from its own territory, in 1967. Its second satellite followed 35 years later, when FedSat was launched in December 2002. Australia has experts in many areas of space science, engineering, and technology, but for most of the last 50 years has had no coordinated national space effort or dedicated funding for space research. In order to remedy this situation and to organise the space science community, the National Committee for Space Science (Australian Academy of Science) developed the first Decadal Plan for Australian Space Science, which was launched on 27 September 2010. This talk has two parts. The first summarizes the Decadal Plan's vision for Australian space science and space capabilities. It presents some of the scientific themes and goals, together with the science, education, and outreach projects to accomplish them. Flagship projects include: Spaceship Australis, to make Australasia the region for which space weather effects are best measured and modelled from the Sun to the ground; Marabibi Constellation, a nano- and small-satellite constellation mission to study space weather, observe Earth, and develop space technology; and the Sundiver project. Medium projects range from digital radars to image and isotopic analysis laboraties to space propulsion. The second part of the talk identifies and discusses specific opportunities for the University of Sydney in space science and engineering, physics, and geoscience, among other areas. These include the i-INSPIRE project that involves members of the Schools of Physics and Aerospace, Mechanical, and Mechatronic Engineering, links to Marabibi Constellation, and may be the first Australian university spacecraft launched into orbit.
18 April
Prof. Douglas Lin (Kavli Institute for Astronomy and Astrophysics; Peking University; UC Santa Cruz)
Origin, structure, and evolution of Hot Jupiters and Super-Earths
Abstract:
In radial-velocity and transit searches, close-in planets are the first to be found. These planets have most likely formed at much larger distances from their host stars and migrated to their present-day location. I will discuss the implication of various recent discoveries including 1) the mass-period distribution of close-in planets, 2) their mass-radius relationship, 3) the mis-alignment of their orbital angular momentum vector and the spin vector of their host stars, 4) their atmosphere and 5) the dynamical architecture of closely-packed multi-planet systems. Based on these theoretical consideration and population synthesis models, we suggest that 1) sequential core accretion is the dominant mode of the planet formation process, 2) planets have considerable mobility, 3) habitable planets are common, and 4) dynamical evolution of planetary systems is an ongoing process.
2 May
Prof. Igal Galili (Hebrew University of Jerusalem)
Teaching weight and gravitation: historical and philosophical perspectives
Abstract:
We present a review of the development of the weight concept through the history of physics. A conceptual split between weight and gravitation, which were unified in the Newtonian perspective of the 17th century, occurred following the introduction of the principle of equivalence by Einstein in the 20th century. The direct implication of this development, together with the adoption of the new philosophy of physics – operationalism, was to distinguish between weight and gravitation. However, in many physics classes, at schools and universities, as well as in textbooks and curricula, this hundred-year-old development has not been adopted. The education research investigating the implications of such a delay to students’ knowledge will be described in brief. Students’ knowledge after instruction in the gravitational definition of weight could be reduced to several conceptions that impede genuine understanding of the subject. A cultural approach to the teaching of weight will be suggested, together with the synergetic teaching of weightlessness and tides.
9 May
Prof. Chris G. Van de Walle (UC Santa Barbara)
Physics and applications of hydrogen in materials
Abstract:
The prospect of using hydrogen as a fuel (for instance in fuel-cell powered cars) lends additional urgency to understanding the physics of hydrogen interactions with materials. State-of-the-art first-principles calculations have allowed us to elucidate the many facets of this behavior. A systematic study of hydrogen in a wide range of hosts has revealed the existence of a universal alignment for the electronic level of hydrogen in semiconductors, insulators, and even aqueous solutions. The alignment allows the prediction of the electrical activity of hydrogen in any host material, and shows that the physics of hydrogen turns out to be unexpectedly connected to other important problems in materials physics and electrochemistry.
23 May
A./Prof. Ofer Gal (Unit for the History and Philosophy of Science, University of Sydney)
High Power Astronomy, the Birth of Optics, and the Death of the Observer
Abstract:
Modern optics was born as an attempt to justify high-power observational astronomy. Attempting to legitimize Tycho Brahe’s instruments, Johannes Kepler revolutionized optics by eschewing the traditional ‘visual rays’ and assigning the agency of image production to light alone. This, however, had very disturbing consequences. It turned the eye into a natural object, immersed in causal processes, and deprived it of its privileged position as the telos of optical progression. No longer subservient to reason, retinal images became projections of light bouncing off objects, and vision was interiorized within the human mind. Ironically, the naturalization of the eye estranged observer from visible object and prepared the ground for Descartes’ famous doubt: that we may be completely wrong.
6 June
Prof. Kris Helmerson (Monash University)
Superflow in a toroidal Bose-Einstein condensate: An atom circuit with a tunable weak link
Abstract:
Quantum fluids can exhibit properties such as long-range coherence and superfluidity that make them useful for constructing sensors and other devices. For example, superconducting quantum interference devices (SQUIDs) are sensitive magnetic field detectors, and superfluid Helium circuits have been used to detect rotation. Recently, "Atomtronics" or ultracold atomic-gas analogs of circuits and electronic devices, such as diodes and transistors, have been proposed. Of particular interest is the realization of an atomic-gas SQUID analog. In an essential step toward realizing an SQUID analog, I will present the first implementation of a non-trivial, closed-loop atom circuit, and show that it is possible to control the current at the single-quantum level by changing the strength of a weak link.
20 June
A./Prof. David Lancaster (University of Adelaide)
The fabrication and development of a new class of laser written planar waveguide lasers, and an overview of the new IPAS silica fibre fabrication facility
Abstract:
This talk will give an overview of the development of a new class of waveguide lasers in collaboration with Macquarie University. Applications for these lasers include spectroscopy, coherent LIDAR, and infrared countermeasure testing. We are the first group to demonstrate these planar-chip ultrafast-laser direct-written waveguides in fluoride glass. I will give an overview of the fabrication and operation of these devices. Specifically we have developed a new class of thulium doped ~1900nm emitting lasers and we have achieved a 55% slope efficiency with a 125mW output power, thereby placing this device as the most efficient and high power short infrared glass waveguide laser reported.
In the second part of the talk I will give an overview of the now fully commissioned silica fibre manufacturing capability which is based on a modified chemical vapour deposition system.
27 June
Prof. James Binney (University of Oxford)
How do galaxies like ours breathe and how galaxies suffocate
Abstract:
From cosmology we think we know how many baryons there are in the Universe, and only a minority are in galaxies. We think the missing baryons are mostly in hot intergalactic gas. Paradoxically, where this gas is dense enough to be observed the embedded galaxies have ceased forming stars for want of raw material, while where the gas not seen (as around our galaxy), the embedded galaxies seem to be accreting much of the gas from which they form stars. I'll describe a model of how galaxies interact with intergalactic gas that, while crude, is remarkably effective in accounting for disparate bodies of data relating both to external galaxies and our own.
5 July: Special Colloquium
Prof. Alan Title (Stanford University, Lockheed Martin Advanced Technology Center)
The Solar Dynamics Observatory and Global Solar Phenomena
Abstract:
The Solar Dynamics Observatory (SDO) was launched on 11 February 2010 into a geosynchronous orbit that allows it to view the Sun 24/7 and download science data at over 100 megabits/second. SDO carries three instruments, the Helioseismic and Magnetic Imager (HMI) that produces full Sun line-of-sight and vector magnetograms as well as doppler maps for seismic analysis; the Extreme Ultraviolet Variability Experiment (EVE) measures the solar irradiance from spectra that span 0.1 to 105 nm every 10 seconds, and the Atmospheric Imaging Assembly that produces full Sun images over a temperature range from 6000 to 20,000,000 K. AIA consists of 4 telescopes each of which operates in two EUV bands that are narrow enough to isolate spectral lines. In 12 seconds all eight wavelength channels are readout from the 4096x4096 CCD’s carried by each telescope. The high cadence of the observations coupled with the full Sun field of view, the 10,000 to 1 dynamic range of the CCD’s, and the ability to directly downlink all the data in realtime is revolutionizing our understanding of a variety of solar processes. In this talk I will focus on the global nature of flares and Coronal Mass Ejections (CME’s). It will be demonstrated the the Sun can operate collectively over more than 180 degrees of latitude. Current indications are the the large scale topology generated by the surface fields controls the span of violent solar events. Movies will be shown that demonstrate some of these collective events. Also realtime access to the data sets will be demonstrated.
18 July
Dr David Spence (Macquarie University)
Cerium lasers: the Ti:Sapphire of the ultraviolet?
Abstract:
Light sources with the shortest pulses and broadest wavelength tunability are generally based on infrared lasers - usually the ubiquitous Ti:Sapphire laser. Such lasers have made a tremendous impact on science and technology, yet conversion of their outputs to the shorter ultraviolet wavelengths needed for a wealth of applications often compromise performance and diminish their attractiveness to users.
Cerium lasers are promising sources that operate directly in the ultraviolet, with the potential to generate even shorter pulses than today's infrared lasers, ultimately into the attosecond regime. I will present our current work to unlock this potential of cerium lasers, and discuss the future challenges to overcome before cerium lasers can truly claim to be the Ti:Sapphire of the ultraviolet.
25 July
Dr Pornrat Wattanakasiwich (Chiang-Mai University)
Comparing active-learning methods in first year physics lectures
Abstract:
Lectures have been around for a long time and are likely to remain with us, especially in large first year physics classes. Recent research in physics education suggests that traditional lectures hardly improve students’ understanding and appreciation of physics knowledge even if the instruction includes demonstrations, simulations or computer-aided instruction. Many physics education research studies have shown active-learning methods to be more effective in increasing student learning of physics concepts. These methods promote substantially greater engagement of students in class activities than, for instance, in a traditional lecture. There are several active-learning methods that can be used in the large lecture such as clickers, buzz sessions, and Peer instruction questions etc. This study has focused on teaching thermal lectures (Phys1001) by two active-learning methods; where the first called Interactive Lecture Demonstrations (ILD) requires more explicit active learning strategies than the other, called Interactive Exercises (IE). ILD was implemented in two streams and IE was implemented in the remaining two streams. Thermodynamic Conceptual Survey (TCS) consisting of 35 multiple-choice questions was used to evaluate and compare student learning between the two methods. The talk will focus on the teaching strategies and present data on evaluation and comparison between the two strategies
15 August
Prof John W.V. Storey (University of NSW)
Current and future developments in Antarctic Astronomy
Abstract:
The past few years have seen rapidly increasing interest in Antarctica as an astronomical site. In addition to a strong US presence at the South Pole, new stations are being established on the high plateau by France/Italy (Dome C) , China (Dome A) and Japan (Dome F). This talk will review the characteristics of these sites and discuss the advantages they confer for the solutions of various astronomical problems. It has recently been suggested that a new site, Ridge A, will combine free-atmosphere seeing superior to Dome C with THz transmission even better than at Dome A, and is thus potentially the "best" astronomical site on the planet. A US expedition to take the Australian-built "PLATO" laboratory to Ridge A is planned for next January.
22 August
A./Prof. Eric R. Hudson (UCLA)
Molecular ions: a new addition to the quantum toolbox
Abstract:
The low-energy internal structure of a diatomic molecule, e.g. the electric dipole moment and vibrational, rotational, and Ω-doublet levels, presents a host of opportunities for advances in quantum simulation, precision measurement, cold chemistry, and quantum information. As such, the last decade has witnessed an enormous effort towards producing ultracold molecules in well-defined rovibrational states. Though this work has focused almost exclusively on neutral molecules, a sample of ultracold molecular ions presents interesting possibilities as many of the goals of cold molecule physics can be accomplished with molecular ions, but with the added benefit of a simple, reliable trapping.
We will discuss our implementation of a recent proposal for the production of ultracold molecular ions, the experimental architecture’s applicability as a scalable quantum computation platform, and the surprising results of a recent measurement of chemistry between ultracold atoms and ions in the system.
29 August
Dr John Teufel (National Institute of Standards and Techology)
Cooling and Measurement of Micro-mechanical Motion at the Quantum Level
Abstract: In the longstanding endeavor to access the quantum nature of macroscopic mechanical motion, the experimental challenge is not only that of state preparation, but also one of measurement. The flourishing field of cavity optomechanics, in which an electromagnetic resonance couples to a mechanical oscillator, addresses both of these challenges—providing a nearly ideal architecture for both manipulation and detection of mechanical motion at the quantum level. I present experiments in which the motion of a high-Q, micromechanical membrane couples to a superconducting microwave resonator. When this circuit is probed with microwave light near its resonance frequency, the displacement of the membrane becomes encoded as modulation of this signal. In turn, the scattering of microwave photons also imparts forces back on the mechanical oscillator. These radiation-pressure forces enforce the Heisenberg limits on measurement, and can also be exploited either to cool or to amplify the motion. Thus, a single microwave drive is used both to perform sideband cooling of the mechanical mode and to monitor its displacement with near quantum-limited sensitivity.
I show that this precision measurement can be used to quantify the thermal motion of the membrane as it is cooled with radiation-pressure forces to its lowest energy state—the quantum ground state.
5 September
Dr Cather Simpson (The University of Auckland)
From Chemical Physics to Antarctic Fish Survival – Exploiting Pulsed Lasers
Abstract: 2010 marked the 50th anniversary of the invention of the laser. The laser has come a long way from those early days, when it was an exotic new technology looking for an application. Now lasers are vital tools in virtually every field of scientific advance. In the Photon Factory, a multiuser laser facility at the University of Auckland, we exploit the characteristics of pulsed lasers to further research in physics, chemistry, engineering, biology and medicine. This presentation will focus upon two extremes: ultrafast spectroscopic studies of the fundamental mechanisms of how molecules 'decide' what to do with the energy they absorb in the form of light, and the application of these laser pulses to manufacture a device to investigate how some antarctic fish survive sub-zero temperatures without freezing.
19 September
Dr Duncan Galloway (School of Physics, Monash University)
Probing dense matter in neutron stars via thermonuclear bursts
Abstract:
Substantial uncertainty remains about the properties of matter at and above densities reached in the atomic nucleus. This uncertainty can largely be attributed to the inaccessibility of such conditions to laboratory-based experiments. Neutron stars, the dense remnants of supernova explosions in medium-sized stars,serve as (rather remote and inaccessible) "laboratories" in which to investigate this regime. In particular, space-based X-ray observations of thermonuclear bursts in neutron stars can lead to measurements of neutron star spin, as well as (in principle) constraints on the neutron star mass and radius, sufficient to constrain the (highly uncertain) equation of state. I will present a brief summary of current research in this area as well as some new results and outstanding issues which must be addressed.
10 October
Gavin Greenoak (School of Physics, University of Sydney)
Sunlight, Sunscreens, and Broad Spectrum Evaluation
Abstract:
Australia remains the skin cancer capital of the world and Australian scientists have led the world in sunscreen development. With the rise of the multinational corporation and globalization the photobiological science which must underpin the methods for evaluating skin protection has entered a challenging phase. Sunscreens are therapeutics in Australia and must be tested according to the Australian Standard to support label claims (SPF and Broad Spectrum). Australia was the first country to recognize the importance of UVA (320nm-400nm) and Broad Spectrum protection, and implemented an in-vitro method for measuring the ability of sunscreens to protect from it. With the push to raise the SPF ceiling from 30+ to 50+ the Broad Spectrum test methods have been under review with many contending approaches. A position has been adopted based on the science, and this will be presented together with the broader context in which it may or may not find traction.
17 October
Professor Mahananda Dasgupta (Australian National University)
Nuclear collisions – many-body quantum dynamics in action
Abstract:
Experiments with nuclei far from stability represent an exciting era for science, as they are opening up new frontiers in the fields of quantum physics, nuclear physics, astrophysics, materials and medical technology. Underpinning these advances is the knowledge and understanding of the outcomes of nuclear collision. Collision dynamics at energies near the fusion barrier is most challenging as outcomes are sensitively dependent on the quantum nature of colliding nuclei. Indeed, nuclear collisions, isolated from external environments, are proving to be a unique tool to probe the quantum dynamics of many-body systems. Nuclei are however completely invisible (<10-14 m), and a collision of two nuclei takes only a zeptosecond (10-21 s) - a challenge for experimentalists. I will describe how we unravel collision dynamics through ingenious experiments, providing ‘snapshots’ of this invisible world, that is allowing us to advance our understanding of many body quantum dynamics. Our experiments have shown dramatic effects of quantum coherence, resulting in orders of magnitude increases in fusion. Most recent experiments show a reduction in tunnelling probabilities compared to expectations of standard coherent model of nuclear reactions. The concept of loss of coherence is currently being explored, with interdisciplinary links to current challenges in controlling the interactions of quantum many body systems for practical applications.
24 October
Dr Steven Flammia (California Institute of Technology)
Verification and Characterization of Quantum States and Processes
Abstract:
Recent years have witnessed tremendous progress in laboratory experiments which prepare highly entangled states of quantum many-body systems. As the complexity of these states increases, however, so too does the difficultly in verifying the quality of the experiment by some objective measure and in characterizing any undesired noise processes. In this talk I will discuss several new methods which address both tasks – verification and characterization – using far fewer resources than traditional methods. I will begin by discussing compressive sensing, a result from classical signal processing which can drastically reduce the required number of samples to reconstruct the spectrum of a time-dependent signal. By adapting and extending these methods to the setting of quantum mechanical systems, I will show how to verify and characterize a broad class of quantum experiments using quadratically fewer measurement settings than traditional methods, an improvement which is provably optimal. Next, I will show how ideas from quantum information theory and condensed matter physics allow us to efficiently reconstruct the ground state of any local Hamiltonian of a gapped one-dimensional interacting quantum system. Finally, I will show how to directly verify the quality of any experiment which prepares a pure quantum state using only a constant number of measurement settings, independent of the size of the system.
7 November
Associate Professor Chris Power (International Centre for Radio Astronomy Research, The University of Western Australia)
The Role of Super-Massive Black Holes in Galaxy Formation
Abstract:
Whenever astronomers look carefully at the centres of galaxies, they find evidence for the presence of super-massive black holes (SMBHs), millions to billions of times the mass of our Sun. Surprisingly, the masses of these SMBHs correlate strongly with properties of their host galaxies, such that more massive SMBHs tend to reside in more massive galaxies. Understanding the origin of these so called scaling relations and what they reveal about the influence of SMBHs on the formation and evolution of their host galaxies is one of the big unsolved problems in galaxy formation. In this talk I shall review some of the main results from my recent analytical and numerical work to understand these scaling relations, with particular emphasis on the interplay between SMBH growth and star formation on the one hand, and winds from SMBHs and massive stars on the other. I shall also briefly comment on how next generation cold gas surveys on instruments such as ASKAP can be used to test these models.
14 November
Dr Phil Diamond (CSIRO Astronomy and Space Science)
Water fountains, molecular jets and magnetic fields: the spectacular death of AGB stars
Abstract:
Water fountains are the molecular jets traced by H2O masers that seem to be a short-lived feature in the transitional period between a Sol-type star's time on the Asymptotic Giant Branch and it becoming a planetary nebula. I will present VLBA data on two water fountain sources and show how the jets may be responsible for the shaping of planetary nebula.
21 November
A/Prof Jeremy Lin (University of Hong Kong)
The Enigmatic Nebula at the Center of the Perseus Cluster
Abstract:
Ever since its discovery over half a century ago, the spectacular nebula associated with the central giant elliptical galaxy of the Perseus cluster, NGC 1275, has been an enigma: its origin, composition, excitation, and fate remain a subject of passionate debate. Today, we know that such optically-luminous nebulae are a common feature of the central elliptical galaxies of dynamically-relaxed galaxy groups and clusters. In such groups and clusters, the hot X-ray-emitting gas that permeates the group or cluster ought to be cooling rapidly in the central region, and thus depositing massive amounts of cool gas (perhaps the source of the nebula?) into the central elliptical galaxy. The active galactic nucleus (AGN) of the central galaxy, however, is believed to reheat the surrounding gas, thus mitigating the amount of gas that cools. The same physical processes are believed to be the central players in the assembly and growth of massive galaxies in the early Universe, among which the descendents are the central elliptical galaxies of galaxy groups and clusters. I review current understanding of the composition, excitation, origin, and fate (star formation, AGN fueling) of the nebula associated with NGC 1275, emphasizing observational tests of models for the nature of this nebula. From this body of work, I draw important lessons for interpreting observational data on the assembly and growth of massive galaxies in the early Universe, and caution against simple straightforward interpretations.
28 November
Professor Nicholas Kaiser (Institute for Astronomy, University of Hawaii)
The Pan-STARRS Wide-Field Imaging Survey
Abstract:
The Pan-STARRS PS1 telescope has been fully operational and surveying
the sky for approximately 1.5 years. It will shortly be joined by
the second telescope PS2. The PS1+2 system will be the world's most
powerful wide-field survey instrument. In this talk I shall describe
the Pan-STARRS design and review the performance of PS1; highlight some
early science results; and describe the plans for operation of PS1+2
and the synergies that this will allow with other up-coming missions
such as Euclid and eRosita and other ground-based surveys.