Taft Armandroff has served as Director of the W.M. Keck Observatory since July 1, 2006. His talk will include recent progress at Keck Observatory on new instruments, telescope and instrument upgrades, and plans for the future. A number of instrumental initiatives are underway, including a detector upgrade for the red arm of LRIS, the new multi-object infrared spectrograph MOSFIRE, and the MAGIQ guider enhancement / replacement project. Adaptive optics enhancements that will be discussed include enabling laser-guide-star adaptive optics on the Keck I telescope, in addition to the existing system on Keck II, and the design of a next-generation adaptive optics system and related instrumentation. Statistics on the scientific output and impact of Keck Observatory will also be featured.

The lecture is free, but as seating limited, please contact Carolyn Cliff 03 9214 5569 or ccliff@swin.edu.au to reserve a seat. Location: AR104

The lecture is free, but as seating limited, please contact Carolyn Cliff 03 9214 5569 or ccliff@swin.edu.au to reserve a seat. Location: AR104

We explore how light behaves near massive objects, and show that for gravitational lenses, gravitational redshifts and black holes, the main concepts can be understood in general terms from Einstein's oft-quoted equation, E=mc^2.

Light paths are changed as they pass close to the sun and to massive galaxies, so giving us the idea of gravitational lenses which can change the appearance of distant galaxies and quasars. Some examples of multiply imaged quasars and lensed galaxies are given.

Gravitational redshifts of light from compact stars have been measured. In the extreme case of very compact objects - black holes - no light can escape at all. There are compelling reasons for believing that massive black holes reside near the centers of many galaxies, and particularly the center of the Milky Way.

Flyer

Understanding the nature and evolution of galaxy clusters places important constraints on cosmological models. Currently, radio observations do not feature heavily among the diagnostic tools used to investigate galaxy clusters. However, recent results suggest that deep radio observations could provide important constraints on the precise dynamical state of galaxy clusters. Increasingly there is evidence to suggest that radio phenomena such as relics, halos, head-tailed galaxies and excessed of low-powered radio galaxies probe the dynamical history of clusters by tracing different phases and conditions. I will present an overview of the new results my students and I have obtained on using radio emission to probe the cluster environment including evidence to suggest that head-tailed galaxies trace the mass density of clusters and that radio luminosity functions suggest late stage mergers act to suppress the AGN population in clusters while at the same time triggering tidally induced starformation along preferred axes.

(1) Observed intensities of forbidden and recombination lines in many nebulae differ from their predicted values by more than an order of magnitude, which has caused emission-line abundances to be called into serious question. We have used HST/STIS to independently derive nebular ion column densities from UV spectra of PNe central stars. We find good agreement with emission measures derived from the nebular forbidden lines, validating the use of forbidden lines in abundance determinations. (2) A high-resolution spectroscopic survey of novae has revealed short-lived heavy element absorption systems near maximum light, consisting of enriched Fe-peak and s-process elements. The absorbing gas is circumbinary and it pre-exists the outburst. Its origin appears to be mass ejection from the secondary star, presumably the result of large episodic mass transfer events from the secondary that initiate the nova outburst. The spectra of SNe Ia should be searched for such systems as they would confirm mass transfer binaries as SNe Ia progenitors.

The results of a spectroscopic search with the AAT's 2dF multi-fibre spectrograph for candidate members of the unusual globular cluster Omega Centauri at and beyond the cluster tidal radius will be presented. Both radial velocity and line strength information is used to identify possible candidate members. The outcome is a limit on the fraction of the total cluster mass contained in the region between 1 and 2 cluster tidal radii, and will be discussed in the context of theories which postulate that Omega Centauri is the remnant nucleus of a tidally disrupted dwarf galaxy

Recent observations from several near-IR selected samples, such as ours from the Gemini Deep Deep Surve,y have found substantial evidence for considerable size evolution in the population of massive elliptical galaxies at z>1.4. I will talk about the discovery of this phenomenon and the real challenge it presents for our models of galaxy evolution, with special attention to the 'red nuggets', massive r<1 kpc elliptical galaxies seen at this epoch, but which have completely disappeared today.

A succesful model for the nature of the quasar accretion process involves the UV/optical continuum arising from a geometrically thin, optically thick cold accretion disk, and the X-ray continuum arising from a hot, optically thin corona that Compton upscatters the disk UV photons. While it appears that the basic ingredients of the quasar engine are currently understood, a number of uncertainties remain, including the source of the viscosity that drives the accretion process, and the nature of the X-ray emitting region. Recently, it has become possible to investigate the dependence of quasar emission on black hole mass, enabling new opportunities for observationally constraining quasar structure. In this talk I will review techniques for estimating black hole mass in unobscured quasars. I will then discuss our recent work on studying how quasar optical/UV and X-ray emission depends on black hole mass and Eddington ratio, as well as how the variability properties of quasars depend on these quantities. I will discuss our results within the context of quasar structure and black hole feedback.

Nature has provided us with superb cosmic clocks that are observable as pulsating radio sources - pulsars. Discovered in Cambridge more than 40 years ago, about 1800 are known by now, most of them discovered with the Parkes telescope in NSW. Pulsars are useful tools in studying fundamental physics, ranging from the properties of super-dense matter to tests of Einstein's theory of gravity, and from physics under extreme conditions to cosmology. This talk will summarize the most fascinating applications of pulsars and will also cast a look into the future where gigantic telescopes will revolutionize our observations of pulsars and potentially our understanding of physics.

Flyer

The lecture is free, but as seating limited, please contact Carolyn Cliff 03 9214 5569 or ccliff@swin.edu.au to reserve a seat.

We have undertaken a deep, wide-field HI imaging survey of M31, reaching a maximum resolution of about 50 pc and 2 km/s across a 95x48 kpc region. The HI mass and brightness sensitivity at 100 pc resolution for a 25 km/s wide spectral feature is 1500 M_Sun and 0.28 K. Our study reveals ubiquitous HI self-opacity features, discernible in the first instance as filamentary local minima in images of the peak HI brightness temperature. Local minima are organized into complexes of more than kpc length and are particularly associated with the leading edge of spiral arm features. Just as in the Galaxy, there is only patchy correspondence of self-opaque features with CO(1-0) emission. We have produced images of the best-fit physical parameters; kinetic temperature, opacity-corrected column density and non-thermal velocity dispersion, for the brightest spectral feature along each line-of-sight in the M31 disk. Spectroscopically opaque atomic gas is organized into filamentary complexes and isolated clouds down to 100 pc. Localized opacity corrections to the column density exceed an order of magnitude in many cases and add globally to a 30% increase in the atomic gas mass over that inferred from the integrated brightness under the usual assumption of negligible self-opacity. Opaque atomic gas first increases from 20 to 45 K in kinetic temperature with radius to 12 kpc but then declines again to 20 K beyond 20 kpc. We have extended the resolved star formation law down to physical scales more than an order of magnitude smaller in area and mass than has been possible previously. The relation between total-gas-mass- and star-formation-rate-density is significantly tighter than that with molecular-mass and is fully consistent in both slope and normalization with the relation found in the molecule-dominated disk of M51 at 500 pc resolution. Below a gas-mass-density of about 5 M_Sun pc^-2, there is a down-turn in star-formation-rate-density which may represent a real local threshold for massive star formation at a cloud mass of about 5x10^4 M_Sun.

G333 Survey is a multi-wavelength survey of the G333 / RCW 106 region, aiming to put together a comprehensive picture of massive star formation throughout an entire giant molecular cloud complex. The aim of the project is to answer observationally some of the key questions about the dynamical processes surrounding massive star formation (e.g. massive stellar winds and large-scale galactic flows) and their relative importance in regulating the star formation process. These dynamical processes drive the turbulent motions which are ubiquitous in giant molecular clouds (GMCs). We have used the new broadband capabilities of the Mopra telescope to map the distribution of around 20 different molecules in an approximately 1 degree square region of the southern Galactic plane (the G333.6-0.2 giant molecular cloud complex). The multi-molecular line nature of this survey is what distinguishes it from similar surveys, and is crucial for gaining a clear picture of the energetics and dynamics of the gas. Different molecular transitions trace different regions of gas in terms of density and excitation, and so can be used to follow energy transfer through the molecular cloud complex. Our initial investigations of the spatial power spectrum of molecules which trace different critical densities show a picture where turbulence is injected at large scales (hundreds of parsecs), and passes through to smaller parsec scales without significant dissipation.

The Red-Sequence Cluster Survey (RCS2) is a 1000-square-degree, multi-color imaging survey carried out using MegaCam on the 3.6m CFHT which is optimized for the search of galaxy clusters at 0.15