We present molecular line mapping of the Giant Molecular Cloud G1.6-0.025,
which is located at the high longitude end of the Central Molecular Zone of our
Galaxy. We assess the degree of star formation activity in that region using
several tracers and find very little. We made a large scale, medium (2')
resolution map in the J = 2-1 transition of SiO for which we find clumpy
emission over a ~0.8 x 0.3 degree-sized region stretching along the Galactic
plane. Toward selected positions we also took spectra in the easy to excite
J_k=2_k-1_k quartet of CH3OH and the CS 2-1 line. Throughout the cloud these
\meth lines are, remarkably, several times stronger than, both, the CS and the
SiO lines. The large widths of all the observed lines, similar to values
generally found in the Galactic center, indicate a high degree of turbulence.
Several high LSR velocity clumps that have 0-80 km/s higher velocities than the
bulk of the molecular cloud appear at the same projected position as "normal"
velocity material; this may indicate cloud-cloud collisions. Statistical
equilibrium modeling of the CH3OH lines observed by us and others yield
relatively high densities and moderate temperatures for a representative dual
velocity position. We find 8 10^4 cm-3/30 K for material in the G1.6-0.025
cloud and a higher temperature (190 K), but a 50% lower density in a high
velocity clump projected on the same location. Several scenarios are discussed
in which shock chemistry might enhance the CH3OH and SiO abundances in
G1.6-0.025 and elsewhere in the Central Molecular Zone.Comment: 51 pages incl. 9 figures and 6 Tables, ApJ (in press
