New 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
  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 $\timeform{1D.2}
\times\timeform{1D.2}$ (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.
