2003A&A...401..185C

Near-infrared images of the star forming region S87 in the JHK' broad-band filters and H₂ v=1-0 S( 1) narrow-band filter are presented. In the eastern part of the region, the S87E nebula shows a quite complex structure. In the optically thin southern part of the nebula, there is an elongated cavity in the direction aligned with the blue-shifted molecular outflow. A subcluster of twelve young near-infrared sources has been detected in the optically thick northern part of the nebula, where a cone-shaped opaque patch is seen. In the 90"x90" region around S87E, we detected 111 sources with m_K'>15.2mag. From analysis of the JHK' colors of the stars inside S87E, we find that after adjusting for background contamination, more than 40% of all the sources associated with the cluster display infrared excesses. This high fraction of infrared excess sources, along with the evidence of molecular outflow activity near the cluster, suggests that the S87E cluster is very young(∼3-4x10⁶yr). We construct the differential K' luminosity function for S87E and find the overall shape and structure are somewhat different to that of other young clusters. Besides a common turnover at 14mag, there is a prominent peak and still more cluster members with luminosities fainter than 14th magnitude at K' band. Five H₂ regions were also discovered and three of them are associated with the S87E nebula.