  The structure of the high galactic latitude Cometary Globule 12 (CG 12) has
been investigated by means of radio molecular line observations. Detailed, high
signal to noise ratio maps in C18O (1-0), C18O (2-1) and molecules tracing high
density gas, CS (3-2), DCO+ (2-1) and H13CO+ (1-0), are presented. The C18O
line emission is distributed in a 10' long North-South elongated lane with two
strong maxima, CG12 N(orth) and CG12 S(outh). In CG12 S the high density
tracers delineate a compact core, DCO+ core, which is offset by 15" from the
C18O maximum. The observed strong C18O emission traces the surface of the DCO+
core or a separate, adjacent cloud component. The emission in high density
tracers is weak in CG12 N and especially the H13CO+, DCO+ and N2H+ lines are
+0.5 km/s offset in velocity with respect to the C18O lines. Evidence is
presented that the molecular gas is highly depleted. The observed strong C18O
emission towards CG12 N originates in the envelope of this depleted cloud
component or in a separate entity seen in the same line of sight. The C18O
lines in CG 12 were analyzed using Positive Matrix Factorization, PMF. The
shape and the spatial distribution of the individual PMF factors fitted
separately to the C18O (1-0) and (2-1) transitions were consistent with each
other. The results indicate a complex velocity and line excitation structure in
the cloud. Besides separate cloud velocity components the C18O line shapes and
intensities are influenced by excitation temperature variations caused by e.g,
the molecular outflow or by molecular depletion. Assuming a distance of 630 pc
the size of the CG 12 compact head, 1.1 pc by 1.8 pc, and the C18O mass larger
than 100 Msun are comparable to those of other nearby low/intermediate mass
star formation regions.
