ROSAT PSPC Observations of NGC 3079 (Poster paper)

Summary

NGC 3079 is a remarkable spiral galaxy which exhibits an unusual range of nuclear activity. Viewed edge-on, it harbors a reddened LINER (Low Ionization Nuclear Emission-line Region) that is kinematically complex, with several distinct components of Ha emission. It also contains a compact, flat spectrum nuclear radio source, and shows well-defined, kiloparsec-scale radio lobes of considerable complexity, as well as a smaller loop of Hα+[N II] emission extending approximately along the minor axis of the galaxy. The optical emission lines indicate that gas is outflowing from the nucleus in an energetic, bipolar outflow or “galactic superwind.” Armus et al. (1990) have suggested that this wind is driven by a powerful, central starburst. A number of different lines of evidence — its infrared brightness (measured by IRAS, the extended 10 μm emission, the spatially coincident, circumnuclear molecular gas, and the extremely luminous H₂O maser — point to the presence of ongoing, vigorous star formation within the nucleus, in agreement with this idea. However, other authors (e.g., Irwin and Sofue 1992; Filippenko and Sargent 1992) argue that the nuclear activity originates from an AGN, perhaps supplemented by a powerful starburst.

We have obtained ROSAT PSPC observations of NGC 3079 and the adjacent spiral galaxy NGC 3073. Preliminary analysis indicates that X-ray emission from NGC 3079 consists of a point-like source, superposed on lower level emission which is extended by 2.5′ in approximately the same direction as the radio jet, Hα loop, and radio lobes (Figs. 1, 2). The extended emission is roughly coincident with two Hα filaments detected by Heckman et al. (1990), and may consist of either a shell-like or a filled structure.