Molecular Clouds in the North American and Pelican Nebulae: Structures
  We present observations of 4.25 square degree area toward the North American
and Pelican Nebulae in the $J = 1-0$ transitions of $^{12}$CO, $^{13}$CO, and
C$^{18}$O. Three molecules show different emission area with their own distinct
structures. These different density tracers reveal several dense clouds with
surface density over 500 $M_\odot$ pc$^{-2}$ and a mean H$_2$ column density of
5.8, 3.4, and 11.9$\times10^{21}$ cm$^{-2}$ for $^{12}$CO, $^{13}$CO, and
C$^{18}$O, respectively. We obtain a total mass of $5.4\times10^4 M_\odot$
($^{12}$CO), $2.0\times10^4 M_\odot$ ($^{13}$CO), and $6.1\times10^3 M_\odot$
(C$^{18}$O) in the complex. The distribution of excitation temperature shows
two phase of gas: cold gas ($\sim$10 K) spreads across the whole cloud; warm
gas ($>$20 K) outlines the edge of cloud heated by the W80 H II region. The
kinetic structure of the cloud indicates an expanding shell surrounding the
ionized gas produced by the H II region. There are six discernible regions in
the cloud including the Gulf of Mexico, Caribbean Islands and Sea, Pelican's
Beak, Hat, and Neck. The areas of $^{13}$CO emission range within 2-10 pc$^2$
with mass of (1-5)$\times10^3 M_\odot$ and line width of a few km s$^{-1}$. The
different line properties and signs of star forming activity indicate they are
in different evolutionary stages. Four filamentary structures with complicated
velocity features are detected along the dark lane in LDN 935. Furthermore, a
total of 611 molecular clumps within the $^{13}$CO tracing cloud are identified
using the ClumpFind algorithm. The properties of the clumps suggest most of the
clumps are gravitationally bound and at an early stage of evolution with cold
and dense molecular gas.
