Subarcsecond Structure and Velocity Field of Optical Line‐emitting Gas in NGC 1052

Abstract

We have obtained integral field spectra of the low-ionization emission-line region in the galaxy NGC 1052 by using the Kyoto Tridimensional Spectrograph II mounted on the Subaru Telescope. Our high signal-to-noise ratio data with precise template subtraction have revealed weaker features at the nucleus, including the [Fe III] and He II emission lines, as well as a broad component of the Hβ emission. The broad Hβ component suggests the existence of a broad-line region. The spatial structure and velocity field derived from the data cube suggest the existence of three main components: a high-velocity bipolar outflow, low-velocity disk rotation, and a spatially unresolved nuclear component. The outflow axis does not coincide with the disk rotation axis. The opening angle of the outflow decreases with velocity shift from the systemic velocity both in bluer and redder velocity channels. This is explained only if the outflow has intrinsically higher velocity components inside, i.e., in regions closer to the outflow axis. At both sides of the bipolar outflow, we find that the highest velocity components are detached from the nucleus. This gap can be explained by an acceleration of at least a part of the flow or the surrounding matter, or by bow shocks that may be produced by even higher velocity outflow components that are not yet detected. Along the edges of the outflow and extending east-northeast and west-southwest, there exist strong [O III] emission ridges. These are closely related to the radio jet-counterjet structure. The abrupt change in the velocity field of the ionized gas and a large [O ]/Hβ line flux ratio in this region suggest a strong interaction of the jets, and possibly also of some ridge components of the line-emitting gas, with the interstellar matter.