Extinction in the Star Cluster SAI~113 and Galactic Structure in Carina

Abstract

Photometric CCD {\it UBVI}${}_C$ photometry obtained for 4860 stars surrounding the embedded southern cluster SAI~113 (Skiff~8) is used to examine the reddening in the field and derive the distance to the cluster and nearby van~Genderen~1. Spectroscopic color excesses for bright cluster stars, photometric reddenings for A3 dwarfs, and dereddening of cluster stars imply that the reddening and extinction laws match results derived for other young clusters in Carina: E${}_{U-B}/$E${}_{B-V}\simeq 0.64$ and $R_V\simeq 4$. SAI~113 displays features that may be linked to a history of dynamical interactions among member stars: possible circumstellar reddening and rapid rotation of late B-type members, ringlike features in star density, and a compact core with most stars distributed randomly across the field. The group van~Genderen~1 resembles a stellar asterism, with potential members distributed randomly across the field. Distances of $3.90\pm 0.19$ kpc and $2.49\pm 0.09$ kpc are derived for SAI~113 and van~Genderen~1, respectively, with variable reddenings E${}_{B-V}$ ranging from 0.84 to 1.29 and 0.23 to 1.28. The SRC variables CK~Car and EV~Car may be outlying members of van~Genderen~1, thereby of use for calibrating the period-luminosity relation for pulsating M supergiants. More importantly, the anomalous reddening and extinction evident in Carina and nearby regions of the Galactic plane in the fourth quadrant impact the mapping of spiral structure from young open clusters. The distribution of spiral arms in the fourth quadrant may be significantly different from how it is often portrayed.

arXiv comment13 pages, 15 eps figure, in press in the Astronomical Journal

References in corpus (16)

• The Effective Temperature Scale of Galactic Red Supergiants: Cool, But Not As Cool As We Thought
• A Three-Dimensional Map of Milky-Way Dust
• The redMaPPer Galaxy Cluster Catalog From DES Science Verification Data
• Automated search for star clusters in large multiband surveys: II. Discovery and investigation of open clusters in the Galactic plane
• The Distance to the Massive Galactic Cluster Westerlund 2 from a Spectroscopic and HST Photometric Study
• The distance to the young open cluster Westerlund 2
• A study of the Galactic plane towards l = 305
• Assessing potential cluster Cepheids from a new distance and reddening parameterization and 2MASS photometry
• The Ara OB1a association: Stellar population and star formation history
• The Color-Magnitude Diagram of NGC 2264
• WR 38/38a and the ratio of total-to-selective extinction in Carina
• Anchoring the Distance Scale via X-ray/IR Data for Cepheid Clusters: SU Cas
• New Results for the Open Cluster Bica 6 and its Associated Planetary Nebula Abell 8
• The Cepheid Impostor HD 18391 and its Anonymous Parent Cluster
• Testing New Ideas Regarding the Nature of Interstellar Extinction
• An Eclectic View of our Milky Way Galaxy

Cited by in corpus (3)

• Cepheid Abundances: Multiphase Results and Spatial Gradients
• Impact of distance determinations on Galactic structure. I. Young and intermediate-age tracers
• On the existence of young embedded clusters at high Galactic latitude