Competitive accretion in the protocluster G10.6-0.4?

TL;DR

This study uses high-resolution observations to reveal multiple infall motions in a protocluster, supporting the competitive accretion model of star formation, with detailed analysis of dense cores and protostars.

Contribution

First detection of infall towards multiple sources in a protocluster, providing observational support for the competitive accretion model.

Findings

Seven dense cores identified with infall motions

Detection of four infrared protostars in the region

Overall collapse with supersonic infall velocities

Abstract

We present the results of high spatial resolution observations at 1.1 mm waveband, with the Submillimetre Array (SMA), towards the protocluster G10.6-0.4. The 1.1 mm continuum emission reveals seven dense cores, towards which infall motions are all detected with the red-shifted absorption dips in HCN (3--2) line. This is the first time that infall is seen towards multiple sources in a protocluster. We also identified four infrared point sources in this region, which are most likely Class 0/I protostars. Two jet-like structures are also identified from Spitzer/IRAC image. The dense core located in the centre has much larger mass than the off-centre cores. The clump is in overall collapse and the infall motion is supersonic. The standard deviation of core velocities and the velocity differences between the cores and the cloud/clump are all larger than the thermal velocity dispersion. The picture of G10.6-0.4 seems to favor the "competitive accretion" model but needs to be tested by further observations.