Three dimensional interstellar extinction map towards the Galactic Bulge

TL;DR

This paper develops a three-dimensional interstellar extinction map towards the Galactic Bulge by combining multi-band photometry with the Besancon Galaxy model, revealing extinction variations with distance and line of sight.

Contribution

It introduces a novel method to derive 3D extinction maps using color-magnitude diagrams and the Besancon model, including the first detailed analysis of extinction law variations in the Bulge.

Findings

Extinction maps reach up to 10 kpc distance and 35 magnitudes in Av.

High-resolution maps (15' x 15') reveal dust features consistent with other 2D maps.

Detected variations in the near-infrared extinction law across different lines of sight.

Abstract

Studies of the properties of the inner Galactic Bulge depend strongly on the assumptions about the interstellar extinction. Most of the extinction maps available in the literature lack the information about the distance. We combine the observations with the Besancon model of the Galaxy to investigate the variations of extinction along different lines of sight towards the inner Galactic bulge as a function of distance. In addition we study the variations in the extinction law in the Bulge. We construct color-magnitude diagrams with the following sets of colors: H-Ks and J-Ks from the VVV catalogue as well as Ks-[3.6], Ks-[4.5], Ks-[5.8] and Ks-[8.0] from GLIMPSE-II catalogue matched with 2MASS. Using the newly derived temperature-color relation for M giants that match better the observed color-magnitude diagrams we then use the distance-color relations to derive the extinction as a function of distance. The observed colors are shifted to match the intrinsic colors in the Besan\c{c}on model, as a function of distance, iteratively thereby creating an extinction map with three dimensions: two spatial and one distance dimension along each line of sight towards the bulge. Colour excess maps are presented at a resolution of 15' x 15' for 6 different combinations of colors, in distance bins of 1 kpc. The high resolution and depth of the photometry allows to derive extinction maps to 10 kpc distance and up to 35 magnitudes of extinction in Av (3.5 mag in Aks). Integrated maps show the same dust features and consistent values with the other 2D maps. Starting from the color excess between the observations and the model we investigate the extinction law in near-infrared and its variation along different lines of sight.