DR. SUMAN BHATTACHARYA

Current cosmological data from the cosmic microwave background and the distribution of structure on large scales strongly suggest that we live in a Lambda Cold Dark Matter Universe. As more sky surveys come online, this model will be put to further test; given the high level of statistical significance expected, the interpretation of observations will require significantly more accurate predictions of structure formation. Large volume, high-resolution, numerical simulations provide the only way to sufficiently sharpen the precision of current models of structure formation. The speaker will discuss some of the largest scale simulations that have been undertaken. He will discuss the science results about a key ingredient in structure formation models- the notion of the dark matter halo. Halos host clusters and galaxies and it is their spatial statistics that are ultimately measured in surveys. In addition, halo abundance underlies the use of clusters as a cosmology probe while halo profiles are important for a wide range of questions such as accurate modeling of the weak lensing shear power spectrum and how galaxies are distributed within halos. He will discuss recent work on precision calculations of halo profiles. The halo profiles can be characterized in terms of a mass and a concentration following the well-known Navarro-Frenk-White description. He will discuss how the concentration varies as a function of mass. At high mass, the c(M) relation flattens out; moreover, at any mass, the variance of the concentration divided by the mean concentration ~1/3, independent of cosmology and the dynamical state of the halo. The mean c-M relation, however, varies at +/- 30 % level with cosmology. The speaker will discuss how these results compare against the observations of cluster profiles. He will then discuss how these large scale simulations are essential to generate high resolution synthetic sky needed for the current and the upcoming CMB polarization surveys.