Cluster Formation in GGD12-15: Infall Motion with Rotation of the Natal Clump

TL;DR

This study uses molecular line observations to analyze the cluster-forming region GGD12-15, revealing infall motion and rotation in the natal clump, and providing insights into the dynamics of cluster formation.

Contribution

It presents new observational evidence of infall and rotational motions in a massive star-forming clump, supported by comparison with a simple gravitational contraction model.

Findings

Detection of infall motion in the clump.

Identification of rotation in the collapsing core.

Observation of bipolar outflow perpendicular to the elongation.

Abstract

We report results of observations of the GGD12-15 region, where cluster formation is actively taking place, using various molecular emission lines. The C18O (J= 1-0) emission line reveals a massive clump in the region with a mass of ~2800 Mo distributed over ~2 pc. The distribution of the C18O(J= 3-2) emission is similar to that of a star cluster forming therein, with an elliptical shape of ~1 pc in size. A bipolar molecular outflow driven by IRS 9Mc, a constituent star of the cluster, is blowing in a direction perpendicular to the elongated C18O (J= 3-2) distribution, covering the entire clump. There is a massive core with a radius of 0.3 pc and a mass of 530 Mo in the center of the clump. There are two velocity components around the core, which are prominent in a position-velocity (PV) diagram along the major axis of the clump. In addition, a PV diagram along the minor axis of the clump, which is parallel to the outflow, shows a velocity gradient opposite to that of the outflow. The velocity structure strongly indicates the infalling motion of the clump. Comparison of the observational data with a simple model of infalling oblate clumps indicates that the clump is undergoing gravitational contraction with rotation.