Toward Precision Cosmology on Small Scales: A Data-Intensive Approach

Vanderbilt University, Nashville TN

Investigators

Abstract

There is a wealth of information about both cosmology and galaxy formation encoded in small scales, but the relevant physics is poorly understood and computationally prohibitive. Halo-based models bypass this problem by parameterizing the relation between galaxies and dark-matter halos, but contain systematic errors and are not sufficiently accurate for reliable statistical tests. A new data-intensive approach that this team has made computationally tractable constructs realistic catalogs from simulations and measures clustering statistics exactly as is done for real data. This work will move past proof-of-concept to perform stringent tests of the Lambda-Cold-Dark-Matter (LCDM) cosmological model on small scales. The result will be a software emulator that uses a grid of simulations to predict galaxy clustering statistics as a function of both cosmology and galaxy-halo parameters. All mock catalogs and analysis codes will be publicly released, which will enable many additional projects. The project also adds training in the critical area of statistics and data analysis to the current Fisk-Vanderbilt bridge program that helps students from underrepresented groups move into a PhD program. The current system has already been used to test fixed cosmological models against measurements in the Sloan Digital Sky Survey, revealing significant tension with the simplest form of the LCDM plus halo model. This next study will be carried out by identifying optimal measurements, extending the parameterization of the galaxy-halo relation to allow for subtle features (including non-Poisson statistics, spatial and velocity bias, and galaxy assembly bias), and strengthening the modeling pipeline. This will enable the most stringent tests of fixed cosmological models, and probe those subtle features of the galaxy-halo connection that have been added. The final ambitious part of the project is to allow cosmological parameters to vary within the parameter search, by exploiting approximate methods to use a single cosmology simulation to predict the halo distributions of other cosmologies. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.