NGC 6318: a young, highly reddened open cluster in the Galactic center direction

Abstract

Presentamos fotometrıa CCD BVI del cumulo abierto NGC 6318. Recuentos estelares efectuados en la region del cumulo permiten estimar el radio angular de NGC 6318 en ∼ 8’. La comparacion de los diagramas CM con isocronas teoricas del grupo de Ginebra implica: E(B-V) = 1.20 ± 0.05, E(V-I) = 1.55 ± 0.10 y V-MV = 15.45 ± 0.35 (d = 2.1 ± 0.5 kpc) para log t = 8.20 (t = 1.6x108 anos) ˜ y Z = 0.020. Entre los cumulos conocidos en la direccion de NGC 6318, Havlen-Moffat 1 y BH 222 son los mas distantes, en tanto que aquellos ubicados entre 1 y 2 kpc del Sol est´an mas absorbidos que lo que deberıamos esperar si los mismos respetaran una ley de extinci´on cuasi-lineal.

We present CCD BVI photometry for the open cluster NGC 6318. Star counts carried out in the cluster field yield an angular radius of 8.0' for NGC 6318. The comparison of the cluster CMDs with isochrones of the Geneva group yields E(B-V) = 1.20 + 0.05, E(V-I) = 1.55 + 0.10 and V-Mv = 15.45 + 0.35 (d = 2.1 + 0.5 kpc) for log t = 8.20 (t = 160 Myr) and Z = 0.020. Among the known clusters in the line-of-sight of NGC 6318, Havlen-Moffat 1 and BH 222 are the farthest ones, while those located between 1 and 2 kpc from the Sun appear to be more absorbed than those expected to follow a quasi-linear extinction law.