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

G. CARRARO; D. TURNER; D. MAJAESS; G. BAUME; R. GAMEN; J.A. MOLINA LERA

ASTRONOMICAL JOURNAL

IOP PUBLISHING LTD

Lugar: Londres; Año: 2017 vol. 153 p. 156 - 166

0004-6256

Photometric CCD UB VIC 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: EU-B EB-V  0.64 and RV  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 thefield. The group vanGenderen1 resembles a stellar asterism, with potential members distributed randomly across the field. Distances of 3.90±0.19 kpc and 2.49±0.09 kpc are derived for SAI113 and vanGenderen1, respectively, with variable reddenings EB-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 evidentin 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.