Velocity structure in the Orion Nebula.: I.: Spectral mapping in low-ionization lines

High-dispersion echelle spectroscopy in optical forbidden lines of O-0, S+, and S2+ is used to construct velocity-resolved images and electron-density maps of the inner region of the Orion Nebula with a resolution of 10 km s(-1) x 3 x 2. Among the objects and regions revealed in this study are (1) the Diffuse Blue Layer, an extended layer of moderately blueshifted, low-density, low-ionization emission in the southeast region of the nebula; (2) the Red Bay, a region to the east of the Trapezium where the usual correlation between velocity and ionization potential is very weak, and where the emitting layer is very thick; and (3) HH 873, a new redshifted jet to the southwest of the Trapezium.