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Astronomy Colloquium

Thursday, October 18, 2012
12:00 AM
Dennison 807

Distinguished Alumni Catherine Espaillat (CfA) and Matt Walker (CfA) present talks in the Astronomy Colloquium series, and as part of Rackham Graduate School's Centennial Celebration.

Catherine Espaillat: "Characterizing Planet-Forming Disks Around Young Stars"

Theoretical simulations predict that a young planet will interact with the accretion disk surrounding its host star, clearing the material around itself and leaving behind an observational signature in the form of a clearing in the disk. Circumstellar disks with large, inner holes have been detected and are known as "transitional disks." A few years ago, Spitzer identified a new class of "pre-transitional disks" which have gaps rather than holes - they have an inner disk, a gap, and an outer disk. These gapped disks are currently the clearest evidence of disk clearing by planets and serve as signposts to guide young planet searches in the ALMA era.

Matt Walker: "Cold Dark Matter vs. Galactic Dynamics"

I will discuss the ability of the standard Cold Dark Matter (CDM) model to make predictions about galactic structure and dynamics. I will focus on attempts to invoke baryon-physical mechanisms to reconcile cosmological N-body simulations with the well-known 'core/cusp' and 'missing satellite' problems on small scales. Then I will argue that observations of dwarf galaxies have the potential to falsify CDM even in the case that CDM makes no clear predictions about dwarf galaxies.

For more on the Rackham Centennial, visit

Catherine Espaillat & Matt Walker