A Contracting, Turbulent, Starless Core in the Serpens Cluster

Abstract

We present combined single-dish and interferometric CS (2-1) and N2H+ (1-0) observations of a compact core in the northwest region of the Serpens molecular cloud. The core is starless according to observations from optical to millimeter wavelengths, but its lines have turbulent widths and asymmetry. Line profile modeling indicates supersonic inward motions vin 0.34 km s-1 over an extended region L > 12,000 AU. The high infall speed and large extent exceeds the predictions of most thermal ambipolar diffusion models and points to a more dynamical process for core formation. A short (dynamic) timescale, ~105 yr L/vin, is also suggested by the low N2H+ abundance, ~1 × 10−10.