A VLA search for compact radio sources in the explosive molecular outflows DR 21 and G5.89

ABSTRACT We present high-angular-resolution ($\sim 0_{.}1\,\mathrm{ arcsec}$) VLA Ku-band (12–18 GHz) observations of two explosive molecular outflows (EMOs), DR 21, and G5.89, in a search for runaway stars related to these explosive events. In DR 21, we identified 13 compact radio sources (CRS), 9 located in the DR 21core and near the CO streamer ejection region. The radio properties of the CRSs show that three are non-thermal radio emitters, likely magnetically active stars, while the nature of the remaining CRSs cannot be conclusively identified. All detected CRSs are good candidates for follow-up proper motion studies to confirm whether they are runaway stars. We also identify multiple ionized arc-shaped structures that can be fitted with parabolas whose symmetry axes converge to a position coincident with CRSs #11, raising the possibility that this source is the main ionizing star. A re-analysis of the 18 molecular outflow streamers refines the center of the explosive event, which aligns closely with the position indicated by the arcs convergence point, supporting a common stellar origin for the EMOs and the H ii-region. In G5.89, the observations reveal a shell with a square-like morphology. The strong extended emission from this H ii region prevents the detection of weak compact radio sources inside the shell; only two were identified well beyond the shell, and a single parabolic arc was fitted within this region. Overall, arc structures in ionized regions seem to be good tracers of the origin of the ionizing sources.