Spatial Resolution of High-Velocity Filaments in the Narrow-Line Region of NGC 1068: Associated Absorbers Caught in Emission (original) (raw)

2002, Astrophysical Journal

Using the STIS spectrograph on HST 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 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 NE 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 , have ionization parameter U 0.1, and ionized masses ∼ 200 M /n e,4 (n e,4 = 10 4 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 × 10 4 yrs. Between 2. 5-4. 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 NE radio lobe. We argue that the blueshifted knots are ablata from disintegrating molecular clouds that are being photoionized by the 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 AGN.