Revisiting G29.862-0.0044: a jet cavity disrupted by an outflow in a likely young stellar object wide binary system

TL;DR

This study tackles the origin of striking near-IR structures in the distant MYSO G29.862-0.0044 by integrating Gemini-NIFS near-IR IFU data, JVLA 10 GHz radio continuum, and ALMA Band 6 continuum and CO observations at sub-arcsecond resolution to resolve ionized, molecular, and dusty components. It identifies a compact radio source offset by ~0.7 arcsec ($\,sim\,$0.02 pc) from a chemically rich main core, alongside a small-scale southward CO outflow ($\approx0.2$ M⊙; $v_{max}\approx4$ km s−1) and a northwest CO feature co-spatial with near-IR cavities, with H2 Brγ diagnostics indicating UV-driven and shock-excited gas. The authors propose a wide binary scenario in which one component clears a cavity that is subsequently disrupted by the molecular outflow from the other component, thereby reconciling the IR morphology with the CO kinematics. This work demonstrates that multiplicity and outflow–cavity interactions can shape the observed morphologies in high-mass star-forming regions and must be considered when interpreting embedded, clustered star formation at large distances.

Abstract

A few years ago, we investigated MYSO G29.862-0.0044 (YSO-G29), an intriguing star-forming region at a distance of 6.2 kpc. Although the typical disc-jet scenario was proposed to explain the observations, it remained far from conclusive. YSO-G29 was analysed using new observations at near-IR from Gemini-NIFS, at radio continuum (10 GHz) from Jansky Very Large Array (JVLA), and new continuum (1.3 mm) and molecular line data from the Atacama Large Millimeter Array (ALMA). The near-IR observations allowed us to detect emission of H2 1-0 S(1) and Br-gamma lines in YSO-G29, which are compatible with excitation and ionization from UV radiation propagating in a highly perturbed ambient. In addition, some evidence of H2 excitation by collisions were found. The ALMA data show the presence of a conspicuous and collimated molecular outflow propagating southwards, while to the north, an extended molecular feature perfectly surrounded by the Ks near-IR emission appears. The continuum emission at 1.3 mm allowed us to better resolve the molecular cores, one of which stands out due to its high temperatures and rich chemical composition. From the JVLA observations, we discovered a compact radio continuum source, a likely compact Hii region or an ionised jet of a massive protostar, located at ~0.7 arcsec (~ 0.02 pc) from the main millimetre core. In this way, we propose a YSO wide binary system. {We can explain the nature of the intriguing near-IR features previously observed: cone-like structures produced by jets/winds of one of the components of the binary system that cleared out the surroundings were disrupted by a molecular outflow probably from the other component. These results complete the picture of what is happening in YSO-G29, and reveal a phenomenon that should be considered when investigating massive star-forming regions.

Figures (23)

• Figure 1: Three-colour image of a 55$^{\prime\prime}$$\times$45$^{\prime\prime}$ region towards YSO-G29 obtained with Gemini-NIRI in our previous work, showing the J, H, and Ks broad-bands emission in blue, green, and red, respectively. The indicated features correspond to the disc-jet system scenario discussed in areal20.
• Figure 2: Fields observed using Gemini-NIFS superimposed over the Ks image of YSO-G29 obtained with Gemini-NIRI.
• Figure 3: Average spectrum obtained towards Field 1 presented as an example to show the detected near-IR lines.
• Figure 4: Integrated Br$\gamma$ and H$_{2}$ 1--0 S(1) emissions (continuum subtracted) towards Field 1 (yellow contours) superimposed over the Ks image obtained with NIRI. The contours levels are 1.3, 2.1, and 4.0 $\times 10^{-19}$ erg s$^{-1}$cm$^{-2}$ for the Br$\gamma$ line, and 2.6, 3.0, and 3.8 $\times 10^{-19}$ erg s$^{-1}$cm$^{-2}$ for H$_{2}$ 1--0 S(1) line. In both cases the first contours is above 4$\sigma$. Box area is 3$^{\prime\prime}$$\times$3$^{\prime\prime}$.
• Figure 5: Integrated Br$\gamma$ emission (continuum subtracted) towards Field 2 (yellow contours) superimposed over the Ks image obtained with NIRI. The contours levels are 0.7 and 1.2 $\times 10^{-19}$ erg s$^{-1}$cm$^{-2}$. First contour is above 4$\sigma$. Box area is 3$^{\prime\prime}$$\times$3$^{\prime\prime}$.