Clumpy Stellar Halos and Complex Disk Galaxies -- Signatures of Hierarchical Universe
James Bullock
University of California, Irvine
October 23, 2006, 4PM, Steward N210
If the favored Cold Dark Matter (CDM) model of structure formation is
correct, then the first objects to collapse in the Universe are low-mass
systems, which fall together to form progressively larger structures
over time. Our Galaxy system, for example, should have accreted and
subsequently tidally destroyed ~100 low-mass galaxies in the past
~12 Gyr. The roughly 20 satellite galaxies we see around the Milky Way
today would correspond to the residual, surviving population of these
early-collapse objects. The Milky Way and M31 disks are expected to
experience ~6 significant central merger events in the past ~10 Gyr.
Put in this context, near-field observations of the Milky Way and its
environment offer a powerful probe of cosmology and galaxy formation
on small scales (and at early times). I discuss programs to simulate
the formation of Milky Way-type systems within the context the LCDM
concordance cosmological model. I will address the question of whether
thin disk galaxies are stable to the expected merging hierarchy and
how ongoing and future programs in "Galactic Archeology" can reveal
signatures of these events. Similarly, I will discuss how searches for
substructure in the outer halo of our Galaxy provide a test of whether
cosmology is indeed hierchical on small scales.
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