Spatial Resolution of High-Velocity Filaments in the Narrow-Line Region of NGC 1068: Associated Absorbers Caught in Emission?

Using the STIS spectrograph on the Hubble Space Telescope, we have obtained a grid of [O III] λλ4959, 5007 and Hβ emission-line spectra at 0.05"×0.19"" and 60 km s^-1 (FWHM) resolution that covers much of the narrow-line region (NLR) of NGC 1068. We find emitting knots that have blueshifted radial velocities up to 3200 km s^-1 relative to galaxy systemic, are 70-150 pc northeast of the nucleus and up to 40 pc from the radio jet, emit several percent of the NLR line flux but no significant continuum, span a small fraction of the sky as seen from the nucleus, coincide with a region of enhanced IR coronal-line emission, show gradients in radial velocities of up to 2000 km s^-1 in 7 pc, span velocity extents averaged over 0.1"×0.2" regions of up to 1250 km s^-1, and have ionization parameter U>~0.1 and ionized masses ~500 M_solar/n_e,4 (n_e,4=10⁴ cm^-3). The brightest parts of the blueshifted knots are often kinematically contiguous with more massive clouds nearer the jet that are moving with velocities of <=1300 km s^-1 relative to galaxy systemic. However, some knots at 1.5"-2.5" radii appear as bright points in a broken shell of radius ~0.55" (40 pc) that is expanding at up to 1500 km s^-1, implying a dynamical age of ~1.3×10⁴ yr. Between 2.5" and 4.5" from the nucleus, emission is redshifted relative to systemic, a pattern that we interpret as gas in the galaxy disk being pushed away from us by the northeast radio lobe. We argue that the blueshifted knots are ablata from disintegrating molecular clouds that are being photoionized by the active galactic nucleus (AGN), and are being accelerated radiatively by the AGN or mechanically by the radio jet. In their kinematic properties, the knots resemble the associated absorbers seen projected on the UV continua of some AGNs. Based on observations made with the NASA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with proposal ID GO-7353.