ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): Deriving Inclination Angle and Velocity of the Protostellar Jets from their SiO Knots

TL;DR

This study uses shock models to estimate the inclination angles and velocities of protostellar jets from SiO knots, confirming consistency with previous proper motion measurements across multiple sources.

Contribution

Introduces a shock-forming model to derive jet inclination angles and velocities from SiO knots, validated against known proper motion data.

Findings

Inclination angles of jets are consistent with outflow models.

Jet velocities derived from knots match proper motion estimates.

The method applies successfully to multiple protostellar sources.

Abstract

We have selected six sources (G209.55-19.68S2, G205.46-14.56S1$_{-}$A, G203.21-11.20W2, G191.90-11.21S, G205.46-14.56S3, and G206.93-16.61W2) from the Atacama Large Millimeter/submillimeter Array Survey of Orion Planck Galactic Cold Clumps (ALMASOP), in which these sources have been mapped in the CO (J=2-1), SiO (J=5-4), and C$^{18}$O (J=2-1) lines. These sources have high-velocity SiO jets surrounded by low-velocity CO outflows. The SiO jets consist of a chain of knots. These knots have been thought to be produced by semi-periodical variations in jet velocity. Therefore, we adopt a shock-forming model, which uses such variations to estimate the inclination angle and velocity of the jets. We also derive the inclination angle of the CO outflows using the wide-angle wind-driven shell model, and find it to be broadly consistent with that of the associated SiO jets. In addition, we apply this shock-forming model to another three protostellar sources with SiO jets in the literature -- HH 211, HH 212, and L1448C(N) -- and find that their inclination angle and jet velocity are consistent with those previously estimated from proper motion and radial velocity studies.