Nobeyama 45-m mapping observations toward nearby molecular clouds, Orion
  A, Aquila Rift, and M17: Project overview
  We carried out mapping observations toward three nearby molecular clouds,
Orion A, Aquila Rift, and M17, using a new 100 GHz receiver, FOREST, on the
Nobeyama 45-m telescope. In the present paper, we describe the details of the
data obtained such as intensity calibration, data sensitivity, angular
resolution, and velocity resolution. Each target contains at least one
high-mass star-forming region. The target molecular lines were $^{12}$CO ($J =
1 - 0$), $^{13}$CO ($J = 1 - 0$), C$^{18}$O ($J = 1 - 0$), N$_2$H$^+$
($J=1-0$), and CCS ($J_N=8_7-7_6$), with which we covered the density range of
10$^2$ cm$^{-3}$ to 10$^6$ cm$^{-3}$ with an angular resolution of $\sim
20\arcsec$ and a velocity resolution of $\sim$ 0.1 km s$^{-1}$. Assuming the
representative distances of 414 pc, 436 pc, and 2.1 kpc, the maps of Orion A,
Aquila Rift, and M17 cover most of the densest parts with areas of about 7 pc
$\times$ 15 pc, 7 pc $\times$ 7 pc, and 36 pc $\times$ 18 pc, respectively. On
the basis of the $^{13}$CO column density distribution, the total molecular
masses are derived to be $3.86 \times 10^4 M_\odot$, $2.67 \times 10^4
M_\odot$, and $8.1\times 10^5 M_\odot$ for Orion A, Aquila Rift, and M17,
respectively. For all the clouds, the H$_2$ column density exceeds the
theoretical threshold for high-mass star formation of $\gtrsim$ 1 g cm$^{-2}$,
only toward the regions which contain current high-mass star-forming sites. For
other areas, further mass accretion or dynamical compression would be necessary
for future high-mass star formation. This is consistent with the current star
formation activity. Using the $^{12}$CO data, we demonstrate that our data have
enough capability to identify molecular outflows, and for Aquila Rift, we
identify 4 new outflow candidates. The scientific results will be discussed in
details in separate papers.
