The "blue-bulge" infall signature toward IRAS 16293-2422

We present the first detection of the "blue-bulge" infall signature toward a protostellar source. The blue-bulge infall signature can be observed in the centroid velocity maps of protostellar objects when infall dominates over rotation. This infall signature can be detected under a wide variety of source conditions. The detection of the blue-bulge infall signature toward a protobinary system such as IRAS 16293-2422 suggests that detailed studies of gravitational collapse toward a large number of protostellar sources may now be possible. Our CS J = 1 → 6 data appear to be tracing gaseous material in the inner circumbinary core, while the CS J = 5 → 4 and HCO⁺ J = 4 → 3 appear to trace the outer envelope and static core in addition to the inner circumbinary core. The mass accretion rate through the infall region appears to be consistent with an inside-out collapse model for the source. Using three-dimensional radiative transfer models based on the rotating, collapse solution of Terebey, Shu, & Cassen, we derive the infall parameters of the IRAS 16293-2422 cloud core. Our best-fit model suggests that the infall radius of the IRAS 16293-2422 cloud core is ∼39″ (0.03 pc).