Estimation of Faraday Rotation Measures of the Near Galactic Sky Using a Nonstationary Gaussian Process Model: Faster, Better MCMC

• Activity Number: 345
• Type: Contributed
• Date/Time: Tuesday, August 2, 2011 : 10:30 AM to 12:20 PM
• Sponsor: Section on Bayesian Statistical Science
• Author(s): Margaret Short*+ and Philipp Kronberg and Dave Higdon
• Companies: University of Alaska at Fairbanks and Los Alamos National Laboratory and Los Alamos National Laboratory
• Keywords: spatial model ; Faraday Rotation Measure ; MCMC ; process convolution

Abstract

Our primary goal is to obtain a smoothed estimate of the magnetic field generated in and near to the Milky Way by using Faraday rotation measures (RMs). RMs provide an integrated measure of the effect of the magnetic field along the line of sight through the Milky Way to extragalactic radio sources. The ability to estimate the magnetic field generated locally by our Galaxy and its environs will help astronomers and astro-particle physicists distinguish local versus distant properties of the universe, and compute magnetic deflections of the (mysterious) ultra high energy [(> 10^19 eV)] cosmic rays after they enter the Milky Way. We model these data using Bayesian process convolution approach, fitted using MCMC. Our model incorporates nonstationarity by allowing model parameters to vary with galactic latitude. The MCMC is enhanced as well, to deal with the additional computational burden, due to the large data set and to the additional model parameters that are being estimated.