A Very Compact Extremely High Velocity Flow toward MMS 5 / OMC-3 Revealed with ALMA (1811.08060v1)

Abstract: Both high- and low-velocity outflows are occasionally observed around a protostar by molecular line emission. The high-velocity component is called Extremely High-Velocity (EHV) flow,' while the low-velocity component is simply referred as(molecular) outflow.' This study reports a newly found EHV flow and outflow around MMS $5$ in the Orion Molecular Cloud 3 observed with ALMA. In the observation, CO $J$=2--1 emission traces both the EHV flow ($|v_{\rm{LSR}} - v_{\rm{sys}}|$ $\simeq$ 50--100 $\rm{km\ s^{-1}}$) and outflow ($|v_{\rm{LSR}} - v_{\rm{sys}}|$ $\simeq$ 10--50 $\rm{km\ s^{-1}}$). On the other hand, SiO $J$=5--4 emission only traces the EHV flow. The EHV flow is collimated and located at the root of the V-shaped outflow. The CO outflow extends up to $\sim$ 14,000\,AU with a position angle (P.A.) of $\sim79^\circ$ and the CO redshifted EHV flow extends to $\sim$11,000 AU with P.A. $\sim96^\circ$. The EHV flow is smaller than the outflow, and the dynamical timescale of the EHV flow is shorter than that of the outflow by a factor of $\sim 3$. The flow driving mechanism is discussed based on the size, time scale, axis difference between the EHV flow and outflow, and the periodicity of the knots. Our results are consistent with the nested wind scenario, although the jet entrainment scenario could not completely be ruled out.