event
Thursday 10 Jun 2010: Deciphering the Dynamical Impact of Cold Dark Matter Sub-Structure
Dr Sukanya Chakrabarti - University of California - Berkeley, USA
Physics, 4th Floor interaction area 15:30-16:30
The Cold Dark Matter (CDM) paradigm is very successful at explaining the growth of structure on large scales. However, it predicts an excess of structure on sub-galactic scales. This over-abundance of CDM sub-structure in simulations relative to observations of Local Group dwarf galaxies is currently one of the most outstanding problems in astrophysics and cosmology. Motivated by this discrepancy, we ask the question if dark galaxies (or dim dwarf galaxies) can be discovered by their tidal gravitational effects on the gas disks of spiral galaxies. I will focus most of my talk on my recent work (Chakrabarti & Blitz 2009; Chakrabarti et al. 2010) where I analyze observed perturbations in the outskirts of the gas disk of the Milky Way to infer and characterize a dark sub-halo that tidally interacted with our galaxy. By comparing the Fourier amplitudes of a large set of high resolution SPH simulations of the Milky Way tidally interacting with perturbers, I show that the best fit to the simulations occurs for a 1:100 mass ratio perturber with a pericentric approach distance of ~5 kpc. I will also demonstrate a fundamental property of parabolic orbits that allows us to break the degeneracy between the mass of the perturber and the distance of closest approach in the evaluation of the tidal force. Next, I will show recent results that allow us to extend this tidal analysis method and apply it in generality. I will end by discussing results obtained using my radiative transfer code RADISHE to calculate emergent SEDs and images of simulated galaxies along the course of their time evolution that allow us to correlate multi-wavelength observables with dynamical tracers of tidal interactions.
