Gas flows around two young stellar clusters in NGC 2264

Observations of the dust and gas toward two young stellar clusters, IRS 1 and IRS 2, in the NGC 2264 star-forming region are presented. Continuum emission is used to locate the dusty envelopes around the clusters and individual protostars within, and line emission from the J = 3-2 transitions of HCO+ and (HCO+)-C-13 is used to diagnose the gas flows around them. The molecular abundance, velocity centroid, and dispersion are approximately constant across the IRS 1 clump. With these constraints, the self-absorbed HCO+ lines are modeled as a large-scale collapse, with speed v(in) = 0.3 km s(-1) and mass infall rate (M) over dot = 4 x 10(-4) M. yr(-1) falling onto an expanding central core. The signature of large- scale collapse, with a similar speed and mass infall rate, is also found toward IRS 2 but again appears disrupted at small scales. Individual protostars are resolved in this cluster and their size and velocity dispersion show that the stellar system is currently bound and no older than 5 x 10(5) yr, but is destined to become unbound and disperse as the surrounding cloud material is lost.