High-speed, highly ionized jets, knots and loops in the Trapezium cluster of the Orion nebula (M42, NGC 1976)

Spatially resolved profiles of the [O III] 5007 – Å line have been obtained in the vicinity of the Trapezium group of stars in the Orion nebula with the Manchester echelle spectrometer on the William Herschel and Isaac Newton telescopes. Receding, collimated outflows are found in the vicinity of the compact interstellar knots LV 1, 2, 3 and 5. These flows have radial velocities of up to 120 km s –1 with respect to the (local) systemic radial velocity $(\bar{V}_\text {HEL}=26 km {s}^{-1})$. An isolated, highly ionized knot is found with a radial velocity of 81 km s –1, as is a receding, extended (7 arcsec across) feature which is composed of two sheets with positive radial velocities of 94 and 134 km s –1 respectively (again with respect to the systemic radial velocity). The cross-over point between these two velocities is in the close vicinity of the dense knot LV 1. The approaching side of an interstellar shell, of 1-arcmin radius and expanding at 100 km s –1, centred on the Trapezium stars, is also clearly identified. The collimated outflows are first considered as ‘jets’ from young stellar sources (YSOs) embedded in the dense LV knots. However, a model is also considered which involves the high-speed stellar wind from θ1C Orionis. This offers a plausible explanation of all the kinematical and morphological phenomena without invoking localized jets.