For more information on colloquia at the Centre for Astrophysics and Supercomputing please contact Dr. Nikole Nielsen ()
Swinburne Virtual Reality Theatre
Applied Science Building, Room 406
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In this talk, I will describe the results of high resolution simulations designed to investigate the internal properties of dark matter halos with virial masses spanning several orders of magnitude in mass at z=0, from M200 = 1e10 Msun, typical of dwarf galaxy halos, to M200 = 1e15 Msun, typical of clusters, forming in the LambdaCDM cosmology. The parameters of these simulations have been set according to the convergence criteria presented in Power et al. (2003); we find that >1 million particles within r200 are required if we are to reliably resolve the spherically averaged mass distribution within the central 1% of the virial radius, r200.
I shall highlight the main results of this work; in particular, I will consider the constraints on the slope of the density profile at the innermost resolved radius (of order 1% of r200), and discuss its mass dependence; comment on the shape of the density profiles of halos spanning several orders of magnitude in mass; and compare our results with theoretical expectations. I will also address possible mass dependence in the spherically averaged velocity and fields (velocity anisotropy, radial velocity); the shapes of isodensity surfaces within the halos; and the substructure content of the halos. Finally I shall comment on the significance of these results and discuss the implications for the CDM model.
The ISSC is working to a timeline that includes informing governments of the project and presenting a management plan late this year, an initial selection of promising technological concepts as well as the location of the array in 2005, the final selection of concept in 2007, world-wide coordinated proposals to governments for construction money in 2009, start of construction in 2012, and operational status late in the next decade.
There are many technological, political, financial and organisational challenges inherent in this international mega-science project. For example, account has to be taken of different funding cycles, different prior investment histories, different scientific interests, different stages of SKA-specific technology development, and different decision-making cultures in the various regions of the world. This presents a challenge to create an organisational and management structure for the SKA that is "light" but sufficient.
The international LOFAR Consortium plan to choose a site for LOFAR in 2003, and the telescope will become operational in 2006. A Western Australian site is on a short-list of three sites worldwide for the US$100M LOFAR project.
We are preparing a final proposal for hosting LOFAR in Australia and exploring ways in which Australia could join the LOFAR Consortium. In this talk I will outline the status of the LOFAR Project within Australia, and would like feedback on Australia's potential involvement in the international LOFAR Project.
We find that after nulls the drift-pattern is changed and that it can remain stably different for about 150 seconds. With the alias mode known, we can now tie these drift-pattern changes to changes in emission-region geometry. We show that post-null emission originates deeper in the pulsar magnetosphere. Both this emission-height change and the striking increase in carousel-rotation time can be explained by a post-null decrease in gap height. This offers a glance at the circumstances needed to make the pulsar turn off so dramatically.
Other efforts aim at identifying field horizontal-branch A-type stars in the digital HES data base of about 4,000,000 low-resolution (15 Angstroem at Hgamma) spectra. These stars are suitable for determining distances of high-velocity clouds, a crucial step towards understanding their nature.