Distributed Low-Mass Star Formation in the IRDC G34.43+00.24
  We have used deep near-infrared observations with adaptive optics to discover
a distributed population of low-mass protostars within the filamentary Infrared
Dark Cloud G34.43+00.24. We use maps of dust emission at multiple wavelengths
to determine the column density structure of the cloud. In combination with an
empirically-verified model of the magnitude distribution of background stars,
this column density map allows us to reliably determine overdensities of red
sources that are due to embedded protostars in the cloud. We also identify
protostars through their extended emission in K-band which comes from excited
H2 in protostellar outflows or reflection nebulosity. We find a population of
distributed low-mass protostars, suggesting that low-mass protostars may form
earlier than, or contemporaneously with, high-mass protostars in such a
filament. The low-mass protostellar population may also produce the narrow
linewidth SiO emission observed in some clouds without high-mass protostars.
Finally, we use a molecular line map of the cloud to determine the virial
parameter per unit length along the filament and find that the highest mass
protostars form in the most bound portion of the filament, as suggested by
theoretical models.
