Study of interstellar extinction in some young open clusters

Abstract

Interstellar extinction has been studied in 15 open clusters, based on reliable cluster members and precise observational data. Out of these, 10 show nonuniform extinction across the cluster region. Most of these show random variation of color excess over the cluster face except NGC 6530 and 6611, where a systematic spatial variation of reddening is observed. The scatter in color excess does not depend upon the spectral class between O and K. Only in some of the young clusters (age of not greater than 5 million yr) the variation of E(B-V) correlates with luminosity and spectral class, in the sense that brighter cluster members are more highly reddened. The present analysis indicates that there is no uniformity in the relationship of extinction spatially, or with spectral type or luminosity or age, among these clusters and hence, explanation of nonuniform extinction in all young open clusters requires a complicated physical scenario.