Three-dimensional interstellar extinction map toward the Galactic bulge^⋆,⋆⋆

¹ Institut Utinam, CNRS UMR 6213, OSU THETA, Université de Franche-Comté, 41bis avenue de l’Observatoire 25000 Besançon France
e-mail: chen@obs-besancon.fr; mathias@obs-besancon.fr; annie@obs-besancon.fr
² Department of Astronomy, Beijing Normal University, 100875 Beijing, PR China
e-mail: bjiang@bnu.edu.cn
³ Institut d’Astrophysique de Paris, UMR 7095 CNRS, Université Pierre et Marie Curie, 98bis boulevard Arago, 75014 Paris, France
⁴ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
e-mail: ogonzale@eso.org; mrejkuba@eso.org
⁵ Departamento Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Stgo., Chile
e-mail: dante@astro.puc.cl
⁶ Vatican Observatory, V00120, Vatican City State

Received: 25 May 2012
Accepted: 13 November 2012

Abstract

Context. Studies of the properties of the inner Galactic bulge strongly depend on the assumptions made about interstellar extinction. Most of the extinction maps available in the literature lack the information about the distance.

Aims. We combine observations with the Besançon model of the Galaxy to investigate the variations of extinction along different lines of sight toward the inner Galactic bulge as a function of distance. In addition we study the variations in the extinction law in the bulge.

Methods. We constructed color–magnitude diagrams with the following sets of colors: H–Ks and J–Ks from the VVV catalog and Ks–[3.6], Ks–[4.5], Ks–[5.8] and Ks–[8.0] from GLIMPSE-II catalog matched with 2MASS. Using the newly derived temperature−color relation for M giants that match the observed color–magnitude diagrams better we then used the distance−color relations to derive the extinction as a function of distance. The observed colors were shifted to match the intrinsic colors in the Besançon model as a function of distance, thereby iteratively creating an extinction map with three dimensions: two spatial and one distance dimension along each line of sight toward the bulge.

Results. Color excess maps are presented at a resolution of 15′  ×  15′ for six different combinations of colors in distance bins of 1 kpc. The high resolution and depth of the photometry allows us to derive extinction maps to 10 kpc distance and up to 35 mag of extinction in A_V (3.5 mag in A_Ks). 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.