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. D 7 } \times \timeform { 2. D 3 } , 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 { 1 D .2 } \times \timeform { 1 D .2 } ( corresponding 9 pc \times 9 pc ) area with a sensitivity of 0.93 K in T _ { 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 .