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

CARRARO, GIOVANNI; TURNER, DAVID G.; MAJAESS, DANIEL J.; BAUME, GUSTAVO LUIS; GAMEN, ROBERTO; MOLINA LERA, JOSÉ ALEJO

ASTROPHYSICAL JOURNAL

IOP PUBLISHING LTD

Lugar: Londres; Año: 2017 vol. 153

0004-637X

Photometric CCD UB VI C photometry obtained for 4860 starssurrounding the embedded southern cluster SAI 113 (Skiff 8) is used toexamine the reddening in the field and derive the distance to thecluster and nearby van Genderen 1. Spectroscopic color excesses forbright cluster stars, photometric reddenings for A3 dwarfs, anddereddening of cluster stars imply that the reddening and extinctionlaws match results derived for other young clusters in Carina:{E}U-B/{E}B-V≃ 0.64 and {R}V≃4. SAI 113 displays features that may be linked to a history ofdynamical interactions among member stars: possible circumstellarreddening and rapid rotation of late B-type members, ringlike featuresin star density, and a compact core, with most stars distributedrandomly across the field. The group van Genderen 1 resembles a stellarasterism, with potential members distributed randomly across the field.Distances of 3.90 ± 0.19 kpc and 2.49 ± 0.09 kpc arederived for SAI 113 and van Genderen 1, respectively, with variablereddenings {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 vanGenderen 1, thereby of use for calibrating the period?luminosityrelation for pulsating M supergiants. More importantly, the anomalousreddening and extinction evident in Carina and nearby regions of theGalactic plane in the fourth quadrant impact the mapping of spiralstructure from young open clusters. The distribution of spiral arms inthe fourth quadrant may be significantly different from how it is oftenportrayed.