MERLIN Radio Detection of an Interaction Zone within a Binary Orion Proplyd System

Presented here are high angular resolution MERLIN 5 GHz (6 cm) continuum observations of the binary proplyd system LV 1 in the Orion nebula, which consists of proplyd 168-326 SE and its binary proplyd companion 168-326 NW (separation 0.″4). Accurate astrometric alignment allows a detailed comparison between these data and published Hubble Space Telescope (HST) PC Hα and [O III] λ5007 images. Thermal radio sources coincide with the two proplyds and originate in the ionized photoevaporating flows seen in the optical emission lines. Flow velocities of ≈50 km s-1 from the ionized proplyd surfaces and ≥100 km s-1 from a possible microjet have been detected using the Manchester echelle spectrometer. A third radio source is found to coincide with a region of extended, high-excitation, optical line emission that lies between the binary proplyds 168-326 SE/326 NW. This is modeled as a bow shock caused by the collision of the photoevaporating flows from the two proplyds. Both a thermal and a nonthermal origin for the radio emission in this collision zone are considered.