Correlating Infall with Deuterium Fractionation in Dense Cores
  We present a survey of HCO+ (3-2) observations pointed towards dense cores
with previous measurements of N(N2D+)/N(N2H+). Of the 26 cores in this survey,
five show the spectroscopic signature of outward motion, nine exhibit neither
inward nor outward motion, eleven appear to be infalling, and one is not
detected. We compare the degree of deuterium fractionation with infall
velocities calculated from the HCO+ spectra and find that those cores with
[D]/[H] > 0.1 are more likely to have the signature of inward motions than
cores with smaller [D]/[H] ratios. Infall motions are also much more common in
cores with masses exceeding their thermal Jeans masses. The fastest infall
velocity measured belongs to one of the two protostellar cores in our survey,
L1521F, and the observed motions are typically on the order of the sound speed.
