A Highly Reddened Star Cluster Embedded in the Galactic Plane

Abstract

We found a cluster of early-type star candidates embedded in the Galactic plane by using optical to near-infrared broadband imaging. The observed region is around the 10 highly reddened stars found as a possible new and very remote open cluster by Stephenson. The 10 stars are identiÐed as red supergiants, and several similar stars are newly found in our images. Furthermore, 25 early-type star candidates suffering visual extinction of have been identiÐed from various color-magnitude and color-color A V D 11.2 diagrams. These stars are likely to make a star cluster, and we estimate its age and distance to be D107.7 yr and D1.5 kpc, respectively.

The very reddened open clusters Pismis 23 (Lyngå 10) and Stephenson 2

“…The red supergiants are concentrated in the central parts (Fig. 9), confirming results from Stephenson (1990) and Nakaya et al (2001). The high extinction of A V = 11.2 (Nakaya et al 2001) and the colour separation between the bulk of the field MS and the cluster MS (Fig.…”

“…9), confirming results from Stephenson (1990) and Nakaya et al (2001). The high extinction of A V = 11.2 (Nakaya et al 2001) and the colour separation between the bulk of the field MS and the cluster MS (Fig. 9) indicates that an intervening dust layer is present, probably corresponding to the dark cloud LDN 515 (Lynds 1962).…”

“…An age closer to 20 Myr and a distance around 6 kpc appear more likely. This is younger than the 50 Myr and the distance is larger than given by Nakaya et al (2001). The I magnitudes of the supergiants and early type star candidates are compatible between this work and Nakaya et al (2001).…”

“…The images of Nakaya et al (2001), together with the present ones, indicate a cluster of diameter around 4 . Figure 7 shows a I vs. I− Gunn z for the whole field, centered on the object.…”

“…9). Adopting the reddening A V = 11.2 by Nakaya et al (2001), then A I = 6.35, using A I /A V = 0.594 (Schlegel et al 1998).…”