NGC 3079: X-ray emission from the nuclear super-bubble and halo

We report the results of the spatial and spectral analysis of the ROSAT HRI and PSPC observations of the edge-on spiral galaxy NGC 3079. We detected several sources in the field of NGC 3079 with both PSPC and HRI, and complex emission from the inner 5′ around NGC 3079. We have identified possible counterparts for several of the sources outside NGC 3079 by comparison with optical plates and catalogues. The X-ray emission from NGC 3079 has a LX = 3 × 1040 erg s−1 and can be resolved into the following three components: – Extended emission in the innermost region, with LX = 1 × 1040 erg s−1, coincident with the super-bubble seen in optical images. The active nucleus may contribute to the emission as a point source. – Emission from the disk of the galaxy, with LX = 7 × 1039 erg s−1, that can be partly resolved by the HRI in 3 point-like sources with luminosities of ∼ 6 × 1038 erg s−1 each. – Very soft X-shaped emission from the halo, with LX = 6 × 1039 erg s−1, extending to a diameter of 27 kpc. The X-ray luminosity of NGC 3079 is higher by a factor of 10 compared to other galaxies of similar optical luminosity and we argue that this may be caused by the presence of an AGN rather than by starburst activity. The influence of the AGN on the companion galaxies in the NGC 3079 group are discussed.