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

Abstract

Spatially resolved profiles of the {[}O III] 5007-angstrom line havebeen obtained in the vicinity of the Trapezium group of stars in theOrion nebula with the Manchester echelle spectrometer on the WilliamHerschel and Isaac Newton telescopes. Receding, collimated outflows arefound in the vicinity of the compact interstellar knots LV 1, 2, 3 and5. These flows have radial velocities of up to 1 20 km s-1 with respectto the (local) systemic radial velocity (V(HEL)BAR = 26 km s-1).An isolated, highly ionized knot is found with a radial velocity of 81km s-1, as is a receding, extended (7 arcsec across) feature which iscomposed of two sheets with positive radial velocities of 94 and 1 34 kms-1 respectively (again with respect to the systemic radial velocity).The cross-over point between these two velocities is in the closevicinity of the dense knot LV 1.The approaching side of an interstellar shell, of 1-arcmin radius andexpanding at 100 km s-1, centred on the Trapezium stars, is also clearlyidentified.The collimated outflows are first considered as `jets' from youngstellar sources (YSOs) embedded in the dense LV knots. However, a modelis also considered which involves the high-speed stellar wind fromtheta1C Orionis. This offers a plausible explanation of all thekinematical and morphological phenomena without invoking localized jets.