Extranuclear X‐Ray Emission in the Edge‐on Seyfert Galaxy NGC 2992

Abstract

We observed the edge-on Seyfert 1.9 galaxy NGC 2992 with the ACIS CCD array on the Chandra X-Ray Observatory and found several extranuclear (r 3'') X-ray nebulae within 40'' (6.3 kpc for our assumed distance of 32.5 Mpc) of the nucleus. The net X-ray luminosity from the extranuclear sources is ~2-3 ? 1039 ergs s-1 in the 0.3-8.0 keV band. The X-ray core itself (r 1'') is positioned at R.A. 9h45m41 95, decl. -14?19'348 (J2000.0) and has a remarkably simple power-law spectrum with photon index ? = 1.86 and intrinsic NH = 7 ? 1021 cm-2. The near-nuclear (3'' r 18'') Chandra spectrum is best modeled by three components: (1) a direct active galactic nucleus (AGN) component from the wings of the point-spread function or an electron-scattered AGN component, with ? fixed at 1.86, (2) cold Compton reflection of the AGN component with intrinsic absorption NH ~ 1022 cm-2, with approximately the same 0.3-8.0 keV flux as the direct component, and (3) a 0.5 keV low-abundance (Z < 0.03 Z?) thermal plasma, with ~10% of the flux of either of the first two components. The X-ray luminosity of the third component (the soft excess) is ?1.4 ? 1040 ergs s-1, or ~5 times that of all of the detected extranuclear X-ray sources. We suggest that most (~75%-80%) of the soft excess emission originates from a region between radii of 1'' and 3'', which is not imaged in our observation due to severe CCD pileup. We also require the cold reflector to be positioned at least 1'' (158 pc) from the nucleus, since there is no reflection component in the X-ray core spectrum. Much of the extranuclear X-ray emission is coincident with radio structures (nuclear radio bubbles and large-scale radio features), and its soft X-ray luminosity is generally consistent with luminosities expected from a starburst-driven wind (with the starburst scaled from LFIR). However, the AGN in NGC 2992 seems equally likely to power the galactic wind in that object. Furthermore, AGN photoionization and photoexcitation processes could dominate the soft excess, especially the ~75%-80% that is not imaged by our observations.