A Color-locus Method for Mapping $R_V$ Using Ensembles of Stars

TL;DR

This paper introduces a new method to map the variation of the dust extinction parameter $R_V$ across the sky using stellar data from Pan-STARRS1, enabling systematic comparison of dust properties over large Galactic areas.

Contribution

The paper presents a novel, systematic approach to measure angular variations in $R_V$ using ensemble stellar data, improving upon previous isolated cloud studies.

Findings

Methods are self-consistent and agree in overlapping regimes.

Some correlation with high-precision $R_V$ studies in specific regions.

Demonstrates potential for comprehensive Galactic dust mapping.

Abstract

We present a simple but effective technique for measuring angular variation in $R_V$ across the sky. We divide stars from the Pan-STARRS1 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.x