Young stars and protostellar cores near NGC2023

B. Mookerjea1*,G. Sandell2, T. H. Jarrett3and J. McMullin4
1Tata Institute of Fundamental Research, Mumbai 400 005, India
2SOFIA-USRA, NASA Ames Research Center, MS 211-3, Moffett Field, CA 94035, USA
3Spitzer Science Center, California Institute of Technology, Pasadena, CA, 91125, USA
4Joint ALMA Observatory, Av Apoquindo 3650 Piso 18, Las Condes, Santiago, Chile & The National Radio Astronomy Observatory, 520 Edgemont Road Charlottesville, VA 22903-2475, USA

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We present the results of our investigation of the young (proto)stellar population in NGC 2023 and the L 1630 molecular cloud bordering the H ii region IC 434, using Spitzer IRAC and MIPS archive data and JCMT SCUBA imaging. We have performed photometry of all IRAC and MIPS images, and used colour-colour diagrams to identify and classify all young stars seen within a 22ʹ X 26ʹ field along the boundary between IC 434 and L 1630. We identify a total of 95 mid-infrared sources and 5 sub-millimeter cores in our 850 and 450 μm SCUBA images, two (MM1 and MM 3) of which have embedded class 0 or I protostars. We find that HD37903 is the most massive member of a cluster with 20 - 30 PMS stars. We also find smaller groups of PMS stars formed in the Horsehead nebula and another elephant trunk structure to the north of the Horsehead. Our study shows that the expansion of the IC 434 H ii region has triggered star formation in some of the dense elephant trunk structures and compressed gas inside the L 1630 molecular cloud.

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Keywords : ISM: clouds - ISM: dust, extinction - ISM: H ii regions - stars: formation - stars: pre-main sequence