by Shengqi Yang (New York University) , Jahmour Givans (Ohio State University)


14:00 Shengqi Yang

Title: A new calibration method of sub-halo orbital evolution for semi-analytic models


Understanding the non-linear dynamics of satellite halos (a.k.a. “sub-halos”) is important for predicting the abundance and distribution of dark matter substructures and satellite galaxies, and for distinguishing among microphysical dark matter models using observations. Typically, modeling these dynamics requires large N-body simulations with high resolution. Semianalytic models can provide a more efficient way to describe the key physical processes such as dynamical friction, tidal mass loss, and tidal heating, with only a few free parameters. In this talk, I will introduce a fast Monte Carlo Markov Chain fitting approach to explore the parameter space of such a sub-halo non-linear evolution model. We find that jointly fitting for the sub-halo mass and maximum velocity functions can break the degeneracy between tidal stripping and tidal heating parameters, as well as providing better constraints on the strength of dynamical friction. We show that our semi-analytic simulation after calibration can accurately reproduce N-body simulations statistics, and that the calibration results for the two sets of N-body simulations agree at 95% confidence level. Dynamical models calibrated in this work will be important for future dark matter substructure studies.


14:30 Jahmour Givans

Title: Lyman-alpha forest perturbative modeling and improved CMB constraining power


The Lyman-alpha forest is the primary cosmological tracer in the post-reionization Universe at 2<z<6. Many attempts have been made to model the Lyman-alpha flux fluctuation power spectrum using perturbation theory, but most of these either only model large (linear) scales or rely on fitting functions to capture small-scale (nonlinear) behavior. In this talk I will present my work on using perturbation theory to model flux fluctuations at second order. I then show how this model refines our understanding of the importance of one BAO systematic, namely, early Universe streaming velocity between dark matter and baryons. Finally, I will discuss my interest in combining improved broadband modeling of the flux fluctuation power spectrum with CMB data from Stage IV experiments to constrain neutrino masses and test for primordial non-Gaussianity. 

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