High‐Resolution Imaging of Molecular Outflows in Massive Young Stars

We present high angular resolution observations toward two massive starforming regions IRAS 18264-1152 and IRAS 23151+5912 with the Plateau de BureInterferometer (PdBI) in the SiO (J=2-1) and H$^{13}$CO$^{+}$ (J=1-0) lines andat 1.3 mm and 3.4 mm continuum, and with the Very Large Array (VLA) in theNH$_3$ (J,K)=(1,1), (2,2) lines. The NH$_3$ (1,1) and (2,2) emission isdetected toward IRAS 18264-1152 only. For IRAS 18264-1152, the SiO observationsreveal at least two quasi-perpendicular outflows with high collimation factors,and the most dominant feature is a redshifted jet-like outflow with very highvelocities up to about ${\Delta}v=60$ kms$^{-1}$ with respect to the systemicvelocity. The very-high-velocity component (${\Delta}v=22 - 60$ kms$^{-1}$) ofthis outflow is spatially offset from its high-velocity (${\Delta}v=3 - 21$kms$^{-1}$) component. The SiO line profiles and position-velocitycharacteristics of these two components suggest that this outflow can be drivenby an underlying precessing jet. For IRAS 23151+5912, the bipolar but mainlyblueshifted SiO outflow coincides with the inner parts of the single-dish COoutflow. In particular the quasi-parabolic shape of the blueshifted outflowcoincides with the near-infrared nebulosity and is consistent with entrainmentof the gas by an underlying wide-angle wind. The analysis of the molecularoutflow data of the two luminous sources further support high-mass starsforming via a disk-mediated accretion process similar to low-mass stars.Comment: Accepter for publication in The Astrophysical Journa