Near-infrared imaging of the star-forming region AFGL 5157

We present near-infrared images of the star-forming region AFGL 5157 in the JHK' broadband filters and H-2 upsilon = 1-0 S(1) narrowband filter. The images reveal a dense cluster of stars and infrared nebulosities associated with previously known infrared sources. Of 54 near-infrared sources detected in the nebula, NGC 1985, 12 exhibit infrared excesses typical of T Tauri stars, Herbig Ae/Be stars, and protostars. The magnitude and color distribution of the cluster of stars in the nebula are found to be different from those outside the nebular region. The K'-magnitude distribution of the cluster is quite flat, while the noncluster is peaked toward the low magnitude. The [H - K'] color of the cluster also displays 0.3 mag redder than that of the noncluster. The infrared nebula displays a bright nucleus with two spirals extended to the north and south. In light of the color properties of the nebula, we propose a shell model for the nebular structure that could be formed by star-forming activity of the central cluster. Many sources with infrared excesses are found to be embedded in the shell structure. Twelve shocked knots in H-2 emission are observed in the region. The nonaxisymmetric distribution of the knots indicates the presence of multiple outflows in the region. Although we failed to identify the powering sources responsible for some of the HH-like objects, the relationship of the H-2 emission with infrared sources shows that there must be several spatially separated sources exciting the shocked H-2 emission as well as the previously observed H2O masers and molecular outflow. Diffuse H-2 emission is also detected on the shell structure, which supports the shell model of the nebula. This diffuse emission could result from fluorescence by relatively evolved stars in the cluster.