Unless current models of PMS angular momentum evolution are flawed, this indicates that the presence of a companion within a distance of 10-1000 AU does not prevent accretion from occurring onto the primary at a rate similar to that observed for single PMS stars. For the closest systems, this implies that accretion must proceed from the circumbinary disk onto the central stars. Accepted by Astron. This extremely low fraction and low surface density of sources with a near-infrared excess strongly indicates that recent star formation activity has been very low in the outlying region of L1630. Our results are consistent with McKee's model of photoionization-regulated star formation.
Many asymmetric profiles have a single blueshifted peak with a red shoulder, rather than two peaks.
Matching these profiles with an infall model appears to require a departure from front-back spatial symmetry, due perhaps to effects of the bipolar outflow. In each source, H 2 CO line wings show clear evidence of collimated outflow, even where the lower-velocity portion of the profile shows infall asymmetry. The entire function is modeled numerically, with the assumption that a star's mass is proportional to the mass of the piece of cloud in which it forms. The results typically give an IMF with the Salpeter value for the slope and a flattening at a low mass. There is little sensitivity to parameters at masses greater than the cutoff, although slightly shallower IMFs might be expected in regions with high levels of ionization and turbulence.