Revealing Multiple Nested Molecular Outflows with Rotating Signatures in HH270mms1-A with ALMA

Abstract

We present molecular line observations of the protostellar outflow associated with HH270mms1 in the Orion B molecular cloud with ALMA. The ^12 CO ( J = 3−2) emissions show that the outflow velocity structure consists of four distinct components of low (≲10 km s ^−1 ), intermediate (∼10–25 km s ^−1 ) and high (≳40 km s ^−1 ) velocities in addition to the entrained gas velocity (∼25–40 km s ^−1 ). The high- and intermediate-velocity flows have well-collimated structures surrounded by the low-velocity flow. The chain of knots is embedded in the high-velocity flow or jet, which is the evidence of episodic mass ejections induced by time-variable mass accretion. We could detect the velocity gradients perpendicular to the outflow axis in both the low- and intermediate-velocity flows. We confirmed the rotation of the envelope and disk in the ^13 CO and C ^17 O emission and found that their velocity gradients are the same as those of the outflow. Thus, we concluded that the velocity gradients in the low- and intermediate-velocity flows are due to the outflow rotation. Using observational outflow properties, we estimated the outflow launching radii to be 67.1–77.1 au for the low-velocity flow and 13.3–20.8 au for the intermediate-velocity flow. Although we could not detect the rotation in the jets due to the limited spatial resolution, we estimated the jet launching radii to be (2.36–3.14) × 10 ^−2 au using the observed velocity of each knot. Thus, the jet is driven from the inner disk region. We could identify the launching radii of distinct velocity components within a single outflow with all the prototypical characteristics expected from recent theoretical works.

Keywords

• Protostars
• Star formation