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تسجيل مستخدم جديدNew Panoramic View of $^{12}$CO and 1.1 mm Continuum Emission in the Orion A Molecular Cloud. I. Survey Overview and Possible External Triggers of Star Formation
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We present new, wide and deep images in the 1.1 mm continuum and the $^{12}$CO ($J$=1-0) emission toward the northern part of the Orion A Giant Molecular Cloud (Orion-A GMC). The 1.1 mm data were taken with the AzTEC camera mounted on the Atacama Submillimeter Telescope Experiment (ASTE) 10 m telescope in Chile, and the $^{12}$CO ($J$=1-0) data were with the 25 beam receiver (BEARS) on the NRO 45 m telescope in the On-The-Fly (OTF) mode. The present AzTEC observations are the widest $(timeform{1.D7}$ $times$ $timeform{2.D3}$, corresponding to 12 pc $times$ 17 pc) and the highest-sensitivity ($sim$9 mJy beam$^{-1}$) 1.1 mm dust-continuum imaging of the Orion-A GMC with an effective spatial resolution of $sim$ 40$arcsec$. The $^{12}$CO ($J$=1-0) image was taken over the northern $timeform{1D.2} timestimeform{1D.2}$ (corresponding 9 pc $times$ 9 pc) area with a sensitivity of 0.93 K in $T_{rm MB}$, a velocity resolution of 1.0 km s$^{-1}$, and an effective spatial resolution of 21$arcsec$. With these data, together with the MSX 8 $mu$m, Spitzer 24 $mu$m and the 2MASS data, we have investigated the detailed structure and kinematics of molecular gas associated with the Orion-A GMC and have found evidence for interactions between molecular clouds and the external forces that may trigger star formation. Two types of possible triggers were revealed; 1) Collision of the diffuse gas on the cloud surface, particularly at the eastern side of the OMC-2/3 region, and 2) Irradiation of UV on the pre-existing filaments and dense molecular cloud cores. Our wide-field and high-sensitivity imaging have provided the first comprehensive view of the potential sites of triggered star formation in the Orion-A GMC.
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