A rotating molecular jet in Orion

Abstract

We present CO(2−1), 13 CO(2−1), CO(6−5), CO(7−6), and SO(6 5 −5 4 ) line observations made with the IRAM 30 m and Atacama Pathfinder Experiment (APEX) radiotelescopes and the Submillimeter Array (SMA) toward the highly collimated (11• ) and extended (∼2 ) southwest lobe of the bipolar outflow Ori-S6 located in the Orion South region. We report for all these lines, the detection of velocity asymmetries about the flow axis with velocity differences roughly on the order of 1 km s −1 over distances of about 5000 AU, 4 km s −1 over distances of about 2000 AU, and close to the source of between 7 and 11 km s −1 over smaller scales of about 1000 AU. The redshifted gas velocities are located to the southeast of the outflow's axis, the blueshifted ones to the northwest. We interpret these velocity differences as a signature of rotation, but also discuss some alternatives which we recognize as unlikely in view of the asymmetries' large downstream continuation. In particular, any straightforward interpretation by an ambient velocity gradient does not seem viable. This rotation across the Ori-S6 outflow is observed out to (projected) distances beyond 2.5 × 10 4 AU from the flow's presumed origin. Comparison of our large-scale (single dish) and small-scale (SMA) observations suggests the rotational velocity to decline not faster than 1/R with distance R from the axis; in the innermost few arcsecs an increase of rotational velocity with R is even indicated. The magnetic field lines threading the inner rotating CO shell may well be anchored in a disk of a radius of ∼50 AU; the field lines further out need a more extended rotating base. Our high angular resolution SMA observations also suggest this outflow to be energized by the compact millimeter radio source 139-409, a circumbinary flattened ring that is located in a small cluster of very young stars associated with the extended and bright source FIR4.

A molecular survey of outflow gas: velocity-dependent shock chemistry and the peculiar composition of the EHV gas

“…Although our observations seem to represent the first detection of SO in EHV gas, bright SO emission in the jet-like components of the HH211 and Ori-S6 outflows have been recently reported by Lee et al (2010) and Zapata et al (2010), respectively. The jet-like component of these outflows has significantly lower velocity than the components in L1448 and I04166, and their emission does not form distinct EHV features in the CO spectra like those shown in Fig.…”

HERSCHEL/HIFI SPECTRAL MAPPING OF C+, CH+, AND CH IN ORION BN/KL: THE PREVAILING ROLE OF ULTRAVIOLET IRRADIATION IN CH+ FORMATION

“…In a standard gas-phase chemistry (e.g., Liszt et al 2005, p. 187), CO is formed by first producing CO + , via C + + OH ⟶ CO + + H, followed by either CO + + H ⟶ CO + H, or CO + + H 2 ⟶ HCO + + H and HCO + + e ⟶ CO + H. Orion BN/KL is known to be abundant in the products of these reactions, which all proceed relatively fast. Furthermore, high-velocity (∼70-100 km s −1 ) CO from low to very high J levels is observed to correlate well with each of the H 2 (ν=1) outflow peaks (Zapata et al 2010;Peng et al 2012b;Goicoechea et al 2015a). For contrast with the distributions of CH + and C + in relation to the outflow in Figure 26(a), we also show contours of CO ( J=10−9) and OH (1834 GHz triplet) observed with HIFI in Figure 26(b), overlaid onto the H 2 2.12 μm imaging.…”

“…The emission features at −38.9 and +65.6 km s −1 in the Hot Core spectrum ( Figure 5), which are relatively symmetric around the main emission component at 8.7 km s −1 , are at first suggestive of velocities in molecular lines such as HF J=1−0 and H 2 O + J=3/2−1/2 absorptions, or in the wings of broad CO J=1−0 emission that have been associated with the LVF (e.g., Zuckerman et al 1976;Schulz et al 1995;Wilson et al 2001;Gupta et al 2010;Phillips et al 2010;Zapata et al 2010;Peng et al 2012a). However, careful inspection shows that the blueshifted feature can be attributed to H O 2 18 while the redshifted feature is dominated by H 2 S, which have both been modeled by Crockett et al (2014b).…”

Discovery of an Expanding Molecular Bubble in Orion Bn/Kl

“…Interestingly, our SMA observations do reveal the presence of typical shock tracers (e.g., SiO, SO, and SO 2 ) in the bubble. The Orion hot core mentioned earlier is located toward the southeast quadrant of the bubble (see Figure 2), and was recently suggested to be caused by the impact of a shock wave related to the dynamical decay of BN, I, and n onto a dense pre-existing core called the "Extended Ridge" (Zapata et al 2010). To explain the near systemic mean velocity of the hot core, the authors of that suggestion argued that the shock wave must be fairly slow, and interact with a particularly dense and massive material.…”