INTERSTELLAR EXTINCTION IN THE DIRECTION OF THE OPEN CLUSTER M29

Abstract

The interstellar extinction is investigated in a 1.5 deg2 area in the direction of the open cluster M29 (NGC 6913) in Cygnus, centered at R.A. = 20h 24m, decl. = +38° 30′. The study is based on photometric classification of 1110 stars in spectral and luminosity classes down to V = 19 mag using photometry in the Vilnius seven-color system published in Paper I (Milasius et al. 2013). Additionally, in the same area the extinction is investigated using 1147 red clump giants (RCGs), identified by combining selected two-color diagrams of the 2MASS and Spitzer surveys. The investigated area is divided into three parts with different obscuration and in these directions the extinction versus distance plots up to 5 kpc are presented. In the whole area a steep rise of the extinction is observed at a distance of ∼800 pc; it should be related to dust clouds in the Great Cygnus Rift obscuring the stars behind it by AV = 4.0–4.7 mag. RCGs exhibit much larger extinction values, up to = 1.2–1.3 mag in the more transparent areas and 1.45 mag in the northeastern part of the area and above it, where the dust cloud TGU H466 is located. These values of correspond to AV = 10–12 mag. We do not exclude the possibility that the largest values of the extinction belong not to RCGs but to some contaminating intrinsically red AGB stars penetrated through the applied RCG selection constraints. The extinction in the TGU H466 cloud probably originates in two cloud systems—the Great Cygnus Rift at 800 pc and the Cygnus X complex of dust and molecular clouds at 1.3–1.5 kpc.