Near-infrared observations of the massive star forming region IRAS 23151+5912

Near-infrared images and K-band spectroscopy of the massive starforming region IRAS 23151+5912 are presented. The JHK' images reveal an embedded infrared cluster associated with infrared nebula, and the H-2 (2.12 mum) narrowband image provides for the first time evidence of outflow activity associated with the cluster. That the cluster is young can be shown by the high percentage of infrared excess sources and the outflow activity. We suggest an age of the cluster of similar to 10(6) yr. Eight young stars are found in the bright nebular core around IRAS 23151+5912. By the color-magnitude diagrams of the cluster, we found five high-mass YSOs and four intermediate-mass YSOs in the cluster. Eight H-2 emission features are discovered in the region with a scattered and non-axisymmetric distribution, indicating the existence of multiple outflows driven by the cluster. Diffuse H-2 emission detected to the north and to the west of the cluster may result from UV leakage of the cluster. Br-gamma, H-2, and CIV emission lines are found in the K-band spectrum of the brightest source, NIRS 19, indicating the presence of envelope, stellar wind, and shock in the circumstellar environment. We have estimated an 07-09 spectral type for the central massive YSO (20 similar to 30Mcircle dot), with an age of less than 1 x 106 yr.