Star Formation Under the Outflow: The Discovery of a Non-thermal Jet from OMC-2 FIR 3 and Its Relationship to the Deeply Embedded FIR 4 Protostar

Abstract

We carried out multiwavelength (0.7-5 cm), multi-epoch (1994-2015) Very Large Array (VLA) observations toward the region enclosing the bright far-IR sources FIR 3 (HOPS 370) and FIR 4 (HOPS 108) in OMC-2. We report the detection of 10 radio sources, 7 of them identified as young stellar objects. We image a well-collimated radio jet with a thermal free-free core (VLA 11) associated with the Class I intermediate-mass protostar HOPS 370. The jet features several knots (VLA 12N, 12C, 12S) of non-thermal radio emission (likely synchrotron from shock-accelerated relativistic electrons) at distances of ∼7500-12,500 au from the protostar, in a region where other shock tracers have been previously identified. These knots are moving away from the HOPS 370 protostar at ∼100 km s −1 . The Class 0 protostar HOPS 108, which itself is detected as an independent, kinematically decoupled radio source, falls in the path of these non-thermal radio knots. These results favor the previously proposed scenario in which the formation of HOPS 108 is triggered by the impact of the HOPS 370 outflow with a dense clump. However, HOPS 108 has a large proper motion velocity of ∼30 km s −1 , similar to that of other runaway stars in Orion, whose origin would be puzzling within this scenario. Alternatively, an apparent proper motion could result because of changes in the position of the centroid of the source due to blending with nearby extended emission, variations in the source shape, and/or opacity effects.

The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. I. Identifying and Characterizing the Protostellar Content of the OMC-2 FIR4 and OMC-2 FIR3 Regions

“…This estimate is inconsistent with earlier luminosity claims of 700-1000 L by López-Sepulcre et al (2013), which was in part motivated by low-resolution (∼6 ) centimeter flux densities observed from the VLA (Reipurth et al 1999) that were interpreted as an ultra-compact HII region and far-infrared flux densities from the InfraRed Astronomy Satellite (IRAS). Osorio et al (2017) spatially resolved the radio emission of FIR3 and FIR4. With higher resolution VLA data (∼0.…”

Radio jets from young stellar objects

“…It is also possible to follow the birth and proper motions of new radio knots ejected by the star (Marti et al 1995;Curiel et al 2006;Pech et al 2010;Carrasco-González et al 2010aGómez et al 2013;Rodríguez-Kamenetzky et al 2016;Osorio et al 2017). When radio knots are detected very near the protostar, these are most probably due to internal shocks in the jet resulting from changes in the velocity of the material with time.…”

“…The right panels show the spectra of the radio sources. Image adapted from Osorio et al (2017) mainly carried out at the VLA. After the confirmation in 2010 of synchrotron emission in the HH 80-81 radio jet, the improvement in sensitivity of radio interferometers has facilitated higher sensitivity observations at multiple wavelengths of star forming regions, and new non-thermal protostellar jet candidates are emerging (e.g., Purser et al 2016;Osorio et al 2017;Hunter et al 2018;Tychoniec et al 2018;see Fig.…”

Nobeyama 45 m mapping observations toward Orion A. III. Multi-line observations toward an outflow-shocked region, Orion Molecular Cloud 2 FIR 4

“…Multi-epoch, multiwavelength Very Large Array (VLA) observations (Osorio et al 2017) support that the FIR 3 outflow is actually moving toward the FIR 4 region, suggesting that the FIR 3 outflow is interacting with the FIR 4 region (see also González-Garcia et al 2016). These morphological evidences strongly support that the outflow is interacting with the dense gas in this region.…”