* Astronomy

Title: AFGL 5157 NH_3: A new stellar cluster in the forming
Authors: Z. Jiang, Z. Chen, Y.Wang, J. Yang, J. Huang, Q. Zhang, G. Fazio

We present the analysis of Spitzer/IRAC and NIR imaging observation of AFGL 5157, an active star forming region. In the IRAC images, this region shows strong PAH emissions in channel 4 and H_2 emissions in channel 2. Many of the H_2 features are aligned to form jet-like structures. Three bipolar jets in the NH_3 core region and a couple of jets northwest of the core have been identified. We identify the possible driving agents of the bipolar jets and show them to be very young. An embedded cluster has been detected in the NH_3 core; many members in the cluster show their SEDs increasing from JHK bands toward longer wavelength, indicative of their early evolutionary stages. Millimetre and sub-millimetre continuum emissions are found to coincide spatially with these presumable Class 0/I sources, in the NH_3 core and the NW subregion. The existence of H_2 bipolar jets and very young stellar objects suggests that star formation is still going on at present epoch in these subregions. Combining the information from previous studies, we propose a sequential star formation scenario in the whole AFGL 5157 region.

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