Cold DCO(+) cores and protostars in the warm Rho Ophiuchi cloud

Abstract

The decrease of DCO(+) abundance with elevation of a cloud's T(K) is used to identify a cluster of a dozen of the coldest, youngest dense cores embedded in the L1688, L1689, and L1709 clouds in the Rho Ophiuchi complex. Most of the cores in L1688 have T(K) = 12-14 K, about half that indicated by CO throughout L1688. Ten cold dust shell, protostellar IR point sources are embedded within these cores. Not every DCO(+) core contains a protostar, but every protostar with a steep spectral index is found in close association with DCO(+) emission. The rotational axes for all of the Rho Oph DCO(+) cores are parallel to the ambient magnetic field, regardless of whether a core is elongated parallel or perpendicular to the direction of the magnetic field. In the Taurus complex the ambient magnetic field is perpendicular to the axes of the major filaments and will inhibit further concentration of material.