Cluster-forming molecular cloud cores

We model a turbulent cloud core ionized by cosmic rays, having Bonnor-Ebert condensations that are both critically stable and cut off from MHD waves in the core. We take these condensations to be the precursors of stars in clusters. The model predicts that such condensations can exist in 'massive" cores having a FWHM line width greater than 0.9 km s(-1) and a column density greater than 1 x 10(22) cm(-2), as is observed in cluster-forming cores in Perseus, Orion, and Cepheus, but cannot exist in the less turbulent, less opaque "low-mass" cores in Taurus, which have no associated clusters. In cluster-forming cores, these condensations are predicted to have mass similar to 1 M(.) and radius similar to 0.03 pc, consistent with the mass and spacing of most young stars in clusters. Such critically stable, cutoff condensations may be identified by their small size and narrow spectral lines, if observed with sufficient sensitivity, spectral resolution, and angular resolution.