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 "infall asymmetry." Line profile modeling indicates supersonic inward motions v_in 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/v_in, is also suggested by the low N₂H⁺ abundance, ~1 × 10⁻¹⁰.

Subject headings: ISM: individual (Serpens); ISM: kinematics and dynamics; stars: formation

Print publication: Issue 1 (1999 June 10)
Received 1999 March 15, accepted for publication 1999 April 13
Published 1999 April 26