Probing the Loss of Angular Momentum in the HH111 Protostellar System with ALMA

ABSTRACT :
We present the ALMA observations of the HH111 protostellar system in C18O (J = 2−1) and 13CO (J = 2−1) with an angular resolution of ~ 0."2. In this system, a disk is found around the protostar VLA 1 and is deeply embedded in a flattened envelope located at a distance of ~ 400 pc. Previous studies have shown that the outer part of the flattened envelope is infalling toward the center and rotating with conservation of angular momentum [v_phi ∼r^(-1)] and the disk is rotating with a Keplerian rotation [v_phi ∼r^(-0.5)]. More interestingly, the inner part of the flattened envelope is found to be rotating with the angular momentum decreasing toward the center, suggesting a loss of angular momentum there. Here we have modeled the kinematics of the flattened envelope and the disk together in order to derive the rotation profile in the inner envelope and investigate the mechanism that can cause this loss of angular momentum.