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We present molecular-line observations of 94 dark cloud cores identified inthe Pipe nebula through near-IR extinction mapping. Using the Arizona RadioObservatory 12m telescope, we obtained spectra of these cores in the J=1-0transition of C18O. We use the measured core parameters, i.e., antennatemperature, linewidth, radial velocity, radius and mass, to explore theinternal kinematics of these cores as well as their radial motions through thelarger molecular cloud. We find that the vast majority of the dark extinctioncores are true cloud cores rather than the superposition of unrelatedfilaments. While we identify no significant correlations between the core'sinternal gas motions and the cores' other physical parameters, we identifyspatially correlated radial velocity variations that outline two main kinematiccomponents of the cloud. The largest is a 15pc long filament that issurprisingly narrow both in spatial dimensions and in radial velocity.Beginning in the Stem of the Pipe, this filament displays uniformly small C18Olinewidths (dv~0.4kms-1) as well as core to core motions only slightly inexcess of the gas sound speed. The second component outlines what appears to bepart of a large (2pc; 1000 solar mass) ring-like structure. Cores associatedwith this component display both larger linewidths and core to core motionsthan in the main cloud. The Pipe Molecular Ring may represent a primordialstructure related to the formation of this cloud.

The nature of the dense core population in the pipe nebula: core and cloud kinematics from C18O observations