Events at Physics |
Events on Tuesday, February 26th, 2008
- Chaos & Complex Systems Seminar
- Generalising the Reynolds number from turbulence to sand-piles(S.O.C.) to ecosystems
- Time: 12:05 pm
- Place: 4274 Chamberlin Hall
- Speaker: George Rowlands, University of Warwick
- Abstract: Some concepts such as scaling and universality common in the study of fluid turbulence are applied to self-organized criticality and simple predator-prey models more common in the biological field. The common thread is a generalisation of the Reynolds number.
- Astronomy Colloquium
- The Stellar Populations of the Andromeda Spiral Galaxy
- Time: 3:45 pm
- Place: 6515 Sterling Hall (coffee at 3:30 pm in 6521 Sterling)
- Speaker: Jason Kalirai, University of California - Santa Cruz
- Abstract: Simulations of hierarchical galaxy formation suggest that large galaxies such as the Milky Way and Andromeda (M31) should contain extended stellar halos that are chemically distinct (more metal poor) from the inner spheroid. Yet, no such population has been discovered in our nearest neighbor, M31. We report on the first results from a photometric and spectroscopic survey of red giant branch (RGB) stars over a large expanse in M31. Using a new technique based on photometric and spectroscopic diagnostics, we are able to isolate bonafide M31 RGB stars out to a distance five times further than previous studies (165 kpc). In addition to the kinematically cold disk and metal-rich inner spheroid, we find clear evidence for an extended, power law halo component in M31. The spectroscopic and photometric metallicity of this new population is measured independently and found to be metal-poor, [Fe/H] = -1.5. We also present the discovery of a new dwarf spheroidal galaxy in M31 and evidence for spatial and kinematical substructure in the halo. The discovery of this stellar halo puts to rest much of the disparity that has existed between the Milky Way and M31 halos, and brings forth an ideal testbed for detailed simulations of galaxy formation.