Protostars and Planets VI, Heidelberg, July 15-20, 2013
Star Formation Activity in the Long Filamentary Infrared Dark Cloud IRDC G53.2
Kim, Hyun-Jeong (Department of Physics and Astronomy, Seoul National University, Republic of Korea)
Koo, Bon-Chul (Department of Physics and Astronomy, Seoul National University, Republic of Korea)
Davis, Chris (Astrophysics Research Institute, Liverpool John Moores University, United Kingdom)
Infrared dark clouds (IRDCs), seen silhouette against the bright Galactic background in mid-IR, are cold and very dense interstellar clouds with high column densities so that IRDCs are believed to be a probable site where massive stars are forming. In this study, we report star formation activity in the IRDC G53.2, a remarkable IRDC at (l, b)~(53.2, 0.0). The IRDC G53.2, which is well consistent with a CO cloud at v~23km/s (or at d~1.7 kpc), is long with its extent of ~30 pc and shows a number of reddened mid-IR sources distributed along its filamentary structure. We perform photometry of the Spitzer MIPSGAL 24 um data, merge with other published catalogs, and present a catalog of young stellar object (YSO) candidates in the IRDC. The classification of YSO candidates based on their spectral energy distributions and control field analysis to remove fore/background star contamination reveal an active star formation in the cloud with ~300 YSO candidates. We find that the evolutionary phases of the YSO candidates are rather earlier compared to other low-mass star forming regions with ~45% of Class I and Flat Class objects, most of which are concentrated in the region bright in far-IR and millimeter. Ubiquitous molecular hydrogen (H2 at 2.122 um) outflows around the YSO candidates in the IRDC revealed by the UWISH2 data indicate that they are earlier class objects as well. Based on the catalog of YSO candidates, we discuss the population of the YSO candidates in different evolutionary phases, their spatial distribution, and the association with H2 outflows in order to characterize star formation activity in the IRDC.
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