The Highly Collimated Radio Jet of HH 80–81: Structure and Nonthermal Emission

Abstract

Radio emission from protostellar jets is usually dominated by free-free emission from thermal electrons. However, in some cases, it has been proposed that non-thermal emission could also be present. This additional contribution from non-thermal emission has been inferred through negative spectral indices at centimeter wavelengths in some regions of the radio jets. In the case of HH 80-81, one of the most powerful protostellar jets known, linearly polarized emission has also been detected, revealing that the non-thermal emission is of synchrotron nature from a population of relativistic particles in the jet. This result implies that an acceleration mechanism should be taking place in some parts of the jet. Here, we present new high sensitivity and high angular resolution radio observations at several wavelengths (in the 3-20 cm range) of the HH80-81 radio jet. These new observations represent an improvement in sensitivity and angular resolution by

The Extraordinary Outburst in the Massive Protostellar System NGC 6334I-MM1: Flaring of the Water Masers in a North–South Bipolar Outflow Driven by MM1B

“…In a recent 1.3 to 6 cm survey of jets from young massive protostars, 10 of 26 ionized jets showed areas of non-thermal emission in their lobes (spectral index ≈ −0.55), which was interpreted as Fermi acceleration in shocks (Purser et al 2016). Thus, the existence of areas of shock-induced emission like CM2 is not uncommon (also see Rodríguez-Kamenetzky et al 2017). We also note that the projected separation of CM2 from the central driving source (MM1B) is ∼ 3000 au, which is strikingly similar to the projected separation of the masers found in the recent Orion KL outburst from the protostar Source I (3400 au, Hirota et al 2011).…”

CO Multi-line Observations of HH 80–81: A Two-component Molecular Outflow Associated with the Largest Protostellar Jet in Our Galaxy

“…(d) CO (2-1) emission integrated from 19.02 to 19.75 km s −1 , contouring from 30% to 90%, by 15%, of the peak of 1.87 Jy beam −1 km s −1 . In each panel, the background image shows the CO (6-5) outflow and the radio jet the same as those shown in Figure 2, but with the red, blue lobes of the CO (6-5) outflow, and the radio jet coded in red, blue, and green, respectively; two dotted lines outline the outflow cavity wall seen in the IRAC 8 µm image, and two dashed lines depict the range of PAs of the radio knots newly detected in Rodríguez-Kamenetzky et al (2017); a filled ellipse in the lower left corner shows the synthesized beam at FWHM. CO (6-5), (7-6) maps to the CO (3-2) beam.…”

“…The cavity wall seen in the Spitzer IRAC image is delineated by two dotted lines in Figure 4. Most recently, new sensitive and high angular resolution observations resolve the emission knots of the HH 80-81 radio jet into multiple components (Rodríguez-Kamenetzky et al 2017).…”

“…Of our particular interests are the radio knots around the SW tip of the CO (6-5) outflow, which have PAs within a range outlined by two dashed lines in Figure 4 (also see Figure 2 in Rodríguez-Kamenetzky et al 2017). In Figure 4(a), the 13 CO (2-1) emission at v = 3.58-4.31 km s −1 reveals molecular structures along both the cavity wall and the radio jet.…”

“…Could the outflow be driven by the fast jet? The mass flux in the ionized jet is estimated to be (0.6-1) × 10 −6 M ⊙ yr −1 , leading to a momentum rate of (0.6-1) × 10 −2 M ⊙ km s −1 yr −1 by adopting a jet ejection velocity of ∼1000 km s −1 and an ionization fraction of 0.1 (Carrasco-González et al 2012;Rodríguez-Kamenetzky et al 2017). Thus the thrust available from the fast jet is at least an order of magnitude greater than the mechanical force of the molecular outflow (10 −4 -10 −3 M ⊙ km s −1 yr −1 ), indicating that the jet is powerful enough to drive the outflow.…”