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Colloquia Series

For more information on colloquia at the Centre for Astrophysics and Supercomputing please contact Dr. Simon Stevenson and Dr. Stefan Osłowski ()

Swinburne Virtual Reality Theatre
Applied Science Building, Room 406
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2000 Colloquia

Dec. 21 @ 11:00
Erwin de Blok (ATNF)
Title: Low Surface Brightness Galaxy Rotation Curves - Why Cold Dark Matter Still Doesn't Work
Using high-resolution optical rotation curves of Low Surface Brightness (LSB) galaxies I show that their shape is inconsistent with those predicted by Cold Dark Matter (CDM) models. Classical pseudo-isothermal halos fit the data much better indicating LSB halos are dominated by a core. A derivation of the mass profiles of the halos shows a similar picture. Claims in the literature that LSB rotation curves are consistent with CDM and all is well are flawed, as they can be shown to be biased by the effects of resolution and sampling. CDM cannot describe LSB galaxies.
Dec. 7 @ 11:00
Geraint Lewis (AAO)
Title: The Rise and Fall of the Sagittarius Dwarf Galaxy
Recent studies have confirmed that the Galaxy's nearest companion, the Sagittarius Dwarf Galaxy, is being being torn apart due to the tidal stresses it is under. We recently have identified a population of bright carbon stars in the Galactic Halo that trace a stream of stellar debris that has been torn off the Dwarf. The stream is extensive, covering a great circle on the sky. A detailed kinematic study of the stream has allowed us to constrain both the mass distribution in the Galactic Halo, and the dark matter content of the Dwarf, as well as model the history of Dwarf's orbit. We find that no additional interactions or fine tuning are required to explain the Dwarf's current predicament, only that the stellar content of the Dwarf must be wrapped in a halo of dark matter.
Nov. 23 @ 11:00
Michael Drinkwater (Melbourne)
Title: The Sky Identified: The 2dF Fornax Spectroscopic Survey
The Fornax Spectroscopic Survey has used the 2dF spectrograph to identify all objects, both stars and galaxies, in a large area of sky for the first time. Dr. Drinkwater will discuss the following discoveries from the survey, finishing by announcing plans for public release of the data.
  1. Their team has discovered a high-velocity tail to the distribution of Galactic stars extending to 500 km/s. Some of these appear to be giants, not bound to the Milky Way.
  2. They have found a population of unresolved low-redshift star-forming galaxies. These could not have been found by previous galaxy surveys.
  3. They have discovered an entirely new type of low luminosity compact galaxy in the Fornax Cluster. They are using Hubble Space Telescope observations to test their hypothesis that these are the stripped nuclei of dwarf galaxies.
  4. They have the first quasar sample defined simply by a magnitude limit without any of the usual pre-selection criteria (e.g. colour); they find a population of red quasars missed by normal colour-colour selection.
Nov. 3 @ 11:00
Paul Francis (ANU/RSAA)
Title: Pink Quasars
It has long been known that quasars are blue. It was quite a surprise, therefore, when pink quasars were first discovered. It is now clear that at least 50% of all quasars have red or pink colours, and had been missed from all previous surveys. In this talk, Dr. Francis will review the enigmatic class of pink quasars, and our on-going efforts to understand their ghastly colours.