ROSAT OBSERVATIONS OF THE IC-4329A GALAXY GROUP

We report here the results of high-resolution and spectral imaging X-r ay observations, with both the ROSAT HRI and PSPC, of the field surrou nding the nearby (D = 64 Mpc) type 1 Seyfert galaxy IC 4329A and its g iant lenticular companion IC 4329. Many point sources are detected, th e brightest being associated with IC 4329A itself, having an extremely bright X-ray luminosity of 6 x 10(43) erg s(-1), and spectral propert ies compatible with a single power-law model (Gamma = 1.73), with a sp ectral break at 0.7 keV. Two other bright sources are detected associa ted with the companion galaxy IC 4329, and a likely quasar 14' to the south-west. We have also established, through optical observations tak en at the European Southern Observatory, that three further X-ray poin t sources, intriguingly positioned with respect to IC 4329A, are in fa ct nothing to do with the system, and are merely foreground and backgr ound objects. In addition to point source emission, residual, unresolv ed emission is detected surrounding the IC 4329A/ IC 4329 pair, extend ing for some 200 kpc. This emission appears markedly two-component, co mprising of a spectrally hard and smooth component, circularly-distrib uted about the central galaxy pair, and a spectrally soft, more clumpy component, positioned almost entirely to the south-east of IC 4329A. The hard component of the residual emission itself appears two-compone nt, one component being due to the 'wings' of the intensely bright IC 4329A source, the other, apparently due to hot (similar to 1.5 keV) ga s, likely associated with the galaxy group of which IC 4329A and IC 43 29 are members. The soft component of the residual emission may be a l arger version of the superwinds seen around some ultraluminous far-inf rared galaxies, or may even represent a 'stripped wake' of intragroup gas. Evidence for shocked gas due to the central IC 4329A/ IC4329 inte raction is also found between the two central galaxies.