Mapping the Relationship Between Interstellar Dust and Radiation in the Milky Way

Abstract

We present a simple but effective technique for measuring angular variation in R_V across the sky. We divide stars from the Pan-STARRS catalog into Healpix pixels and determine the posterior distribution of reddening and R_V for each pixel using two independent Monte Carlo methods. We find the two methods to be self-consistent in the limits where they are expected to perform similarly. We also find some agreement with high-precision photometric studies of R_V in Perseus and Ophiuchus, as well as with a map of reddening near the galactic plane based on stellar spectra from APOGEE. While current studies of R_V are mostly limited to isolated clouds, we have developed a systematic method for comparing R_V values for the majority of observable dust. This is a proof of concept for a more rigorous galactic reddening map. We also present a method for inferring the three dimensional variation in dust temperature. By combining extinction information from Bayestar17 and emission information from Planck and SFD, we fit a graybody model to each Healpix pixel and generate a map covering 3π steradians and distances from 0.06 kpc to 25 kpc. We compare these results to the above maps of R_V and show that it is possible to probe the physics and composition of interstellar dust by applying simple models to large data sets.