Intracluster extinction in young open star clusters

Abstract

An analysis of near-infrared data in combination with optical observations, indicates a normal interstellar extinction law around hot O and B stars at wavelengths greater than or = 0.9 micrometers. At shorter wavelengths, it can be either normal or anomalous depending upon the physical conditions of intracluster material. In some cases, anomaly is found to be due to a small shift in grain-size distribution towards smaller than normal sized particle, while in other regions, exactly opposite grain size distribution seems to be responsible for the anomaly.