The Nuclear Superbubble of NGC 3079
Session 23 -- Emission-Line, Starburst and Ultra-Luminous Galaxies
Oral presentation, Monday, 2:30-4:00, Wheeler Room

## [23.03] The Nuclear Superbubble of NGC 3079

S. Veilleux (KPNO/NOAO), G. Cecil (U. North Carolina), R. B. Tully (U. Hawaii), J. Bland-Hawthorn (Rice U.), and A. V. Filippenko (UC Berkeley)

Extremely violent gas motions are known to exist in the core and circumnuclear environment of the Sc galaxy NGC 3079 (e.g., Ford et al. 1986; Heckman, Armus, \& Miley 1990; Filippenko \& Sargent 1992). The proximity (16 Mpc), late-type morphology, and edge-on orientation of this galaxy make it an excellent laboratory to study the interaction between the outflowing nuclear gas and the interstellar medium of the host galaxy. The Hawaii Imaging Fabry-Perot Interferometer (HIFI) was used at the Cassegrain focus of the CFH 3.6-meter telescope to produce a large data cube covering H$\alpha$ + [N~II] $\lambda\lambda$6548, 6583 at a resolution of 70 km s$^{-1}$ and with subarsecond spatial sampling. Complementary long-slit spectra obtained with the Palomar 5-meter telescope were also used to provide additional line diagnostics. The complete two-dimensional coverage of the Fabry-Perot data allowed us to derive the general flow pattern of the nuclear gas using a three-Gaussian profile decomposition technique. A conic outflow with monotonically increasing velocities (V $\sim$ R$^n$ with 1.5 $\ltaprx$ n $\ltaprx$ 2.5) and inclined by about 5$^\circ$ from the plane of the sky provides a good first-order fit to the velocity field in the nuclear region. A total mass and kinetic energy of order 10$^7$/n$_e$ M$_\odot$ and 10$^{56}$/n$_e$ ergs, respectively, are involved in this outflow event. An upper limit of $\sim$ 150 cm$^{-3}$ for the electron density is derived from the [S~II] lines (in their low-density limit) and unusual excitation conditions ([N~II] $\lambda$6583/H$\alpha$ much larger than unity) are observed throughout the nuclear region. The implications of these results on the nature of the energy source (starburst versus active nucleus) will be discussed along with the effects of this powerful outflow event on the structure of the galactic disk of the host galaxy.