The Interstellar Reddening Law within 3kpc from the Sun

Abstract

We have investigated the interstellar reddening law of young open clusters within 3kpc from the Sun using optical, near-IR 2MASS, and Spitzer IRAC data. The total-to-selective extinction ratio R V of 162 young open clusters (log t age 7.3) listed in the open cluster database WEBDA is determined from the color excess ratios. The young open clusters in the Sgr-Car arm show a relatively higher R V , those in the Per arm and in the Cygnus region of the local arm show a relatively smaller value, and those in the Mon-CMa region of the local arm show a normal value (R V ≈ 3.1).

Reddening, distance, and stellar content of the young open cluster Westerlund 2

“…We adopt the E(B − V ) f g to be 1.05. We also adopt the foreground reddening law to be R V,f g = 3.33, which agrees with the RV variation within 3kpc from the Sun (Sung & Bessell 2014).…”

“…2, has frequently been confirmed for open clusters, not only in the solar neighborhood(Sung & Bessell 2014), but also beyond the Sagittarius-Carina arm(Westerlund 1-Lim et al 2013; the galactic centre-Rieke & Lebofsky 1985). The normal reddening law of RV = 3.1 ± 0.2 was also assumed in the earlier photometric studies for Wd 2(Moffat et al 1991;Rauw et al 2007) and the distance to the cluster determined to be d ∼ 8 kpc (V0 − MV ∼ 14.5 mag).…”