A parameterized study of the detection of infall in protostellar systems

We report new radiative transfer calculations of submillimeter and millimeter molecular line emission from fully three-dimensional models of protostars. The radiative transfer calculations are performed using the parameterized, semianalytic, rotating collapse solutions of Terebey, Shu, & Cassen. These results are compared with the class of "self-consistent," nonspherical, hydrodynamic, rotating collapse solutions (Boss; Walker, Narayanan, & Boss). We explore the sensitivity of the "blue-bulge" infall signature to rotational rate, infall time, sound speed, and abundance gradients in the molecular tracer of choice. At high angular resolutions, models with moderate to high rotational rates exhibit the "polar blue bulge" - a centroid velocity signature of underlying Keplerian rotation in an embedded cloud core. Submillimeter transitions of HCO⁺ and CS are found to be better than millimeter transitions in detecting infall, especially at early collapse times.