Previous abstract Next abstract
We present new spectroscopic evidence for a galactic-scale superwind in the Seyfert 2 galaxy NGC~2992. Our study is based on a grid of high-resolution long-slit spectra obtained with the RGO spectrograph on the 3.9-m Anglo-Australian telescope.
Emission-line images of NGC~2992 (obtained with the NTT at La Silla, Chile) in the light of \Oiii\ and \HaNii\ reveal a prominent bi-cone or double-bowl shaped Extended Emission-Line Region (EELR) that is likely oriented away from the galactic plane. This EELR can be traced to a projected distance of at least 10--15 kpc (at H$_0$=75 \kmsMpc) from the nucleus. The host galaxy is highly inclined to the line of sight, and the EELR is bisected by a strong dust lane. The opposite sides of the EELR are well focused at the expected position of the nucleus and have parabolic edges. The \Oiii/(\HaNii) line-ratio map shows a complex excitation pattern with several ``arcs'', ``walls'', and other morphological structures indicative of shocks and/or steep density gradients throughout the EELR.
The grid of spectra covers nearly the entire emission-line region. Double-peaked line profiles are detected at most of the slit positions. One of the components, often the strongest, follows a galactic rotation curve. When this rotation is removed, a wind velocity field clearly emerges, indicating that each side is expanding at velocities up to 200 \kms\ with higher velocities generally closer to the nucleus.
Both the shape of the EELR in NGC~2992 and the observed velocity field suggest that the source of the strong wind is highly concentrated and lies in the nuclear region. Possible alternatives for the driving force of this powerful outflow, including a massive starburst and an AGN powered wind, will be discussed.
8:30a program listing