Gravitational Infall in the Dense Cores L1527 and L483

Abstract

Lines of N₂H⁺, C₃H₂, and H₂CO show kinematic evidence of gravitational infall in L1527, and probably also in L483. Three trends appear to indicate infall, rather than outflow or rotation: (a) at each protostar position, line peak and centroid velocities get bluer by 0.1-0.3 km s^-1 with increasing line optical depth; (b) in maps of C₃H₂ and H₂CO lines, peak and centroid velocities get bluer by a similar amount as positions approach each protostar; and (c) C₃H₂ line widths in L1527 increase as positions approach the protostar. Also, in both sources H₂CO lines show the infall "signature" of spatially concentrated double-peaked profiles, with their blue peaks brighter than their red peaks, as seen previously in B335. Many asymmetric profiles have a single blueshifted peak with a red shoulder, or two peaks with blue/red intensity ratio greater than 3. These are hard to fit with spherical infall models, owing perhaps to the effects of the bipolar outflow. In each source, H₂CO line wings show clear evidence of collimated outflow.