1	Astr 5460 Wed., Mar. 5, 2003 Today: Reminders/Assignments Longair, Chapter 4, Clusters Chapter 5 for Friday: - Getting into Theory/GR Unless noted, all figs and eqs from Longair.
2	Reminders/Preliminaries Astro-ph preprints on Friday: http://xxx.lanl.gov/ Galaxy Spectra/Modeling Assignment Reading Bennett et al. 2003 (MAP) paper WIRO cautions, still to be scheduled… Register an account on MAST
3	Galaxy Spectra assignment The textbook is rather weak when it comes to observational properties like spectra – as budding young observers you need to know more! Find and download the galaxy spectra templates of Kinney et al. (1996) – and read the paper! Find and download the spectral synthesis population models of Bruzual and Charlot. “Fit” the elliptical template and one spiral galaxy. Show some plots indicating how broad-band colors change with redshift assuming not evolution (up to z=2). Write up your results like you would for publication with clarity, citations, etc.
4	Gravitational Lensing by Clusters Mass bends space and hence light paths (Einstein 1915; General relativity). Angular deflection by point mass is: Where p is the “collision parameter.” What happens when p goes to zero?
5	Gravitational Lensing by Clusters
6	Gravitational Lensing by Clusters Previous derivation assumes Euclidean geometry (which WMAP says is OK!). Still OK if the distances are angular diameter distances (chapter 5). Expressing the result in physical terms: So, what is the typical size for clusters?
7	Gravitational Lensing by Clusters
8	Gravitational Lensing by Clusters OK, but clusters are not point sources. See discussion on P. 96-97. For our isothermal gas sphere can derive the result that:
9	Gravitational Lensing by Clusters
10	Gravitational Lensing by Galaxies
11	Gravitational Lensing by Galaxies
12	Forms of Dark Matter??? We’re certain it is present. Some is baryonic. More is non-baryonic.
13	Baryonic Dark Matter Protons, Neutrons, electrons (include black holes here too). Text example of bricks (yes bricks!). Brown dwarfs and the like. BB nucleosynthesis constrains baryons to less than 0.036 h^-2 of closure density.
14	Baryonic Dark Matter Black holes constrained by lensing effects (or lack thereof). MACHOs (Alcock et al. 1993):
15	Baryonic Dark Matter MACHOs: http://www.owlnet.rice.edu/~spac250/coco/spac.html MACHOs are rather massive, around half a solar mass, and can contribute up to half of the dark halo mass. White dwarfs???
16	Non-Baryonic Dark Matter I’m no expert on this stuff (and in some sense NO ONE is). Particle physicists play in this area more than astronomers. Leading candidates include Axions. Cold, low mass, avoid strong CP violation. Neutrinos. Hot, low mass (getting better constrained), lots of them. SN helps. WIMPs. Gravitino, photino, etc. Mirror Matter. May use in my next novel.