NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-08-19 T11:42:54 PDT
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For refcode 1996ApJ...468..191P:
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1996ApJ...468..191P X-RAY EMISSION OF ACTIVE GALACTIC NUCLEI WITH CIRCUMNUCLEAR STAR-FORMING RINGS: NGC 1097 AND NGC 7469 DIEGO E. PEREZ-OLEA AND LUIS COLINA Received 1996 January 18; accepted 1996 March 15 ABSTRACT ROSAT high-resolution imager (HRI) observations of the active galaxies NGC 1097 (Liner/Seyfert) and NGC 7469 (Seyfert 1), known to have a circumnuclear star-forming ring, are presented. An extended X-ray emission associated with ring of NGC 1097 is detected in the HRI image of this galaxy. The X-ray luminosity emitted by the ring is L_x_ = 3.6 x 10^40^ ergs s^-1^ and accounts for about 20% of the integrated X-ray luminosity of NGC 1097, L_x_ = 2 x 10^41^ ergs s^-1^. Circumnuclear star-forming rings in active galaxies like NGC 1097 and NGC 1068 have X-rays to radio and H{alpha} luminosities ratios similar to those of pure starburst galaxies like M82, NGC 253, and NGC 1808. On average, starbursts are characterized by L_x_/L_5 GHz_ ~ 400, and L_x_/L_H{alpha}_ ~ 0.14. The HRI image of NGC 7469 shows no structure, and the X-ray emission emitted by the circumnuclear ring cannot be disentangled from that of the nucleus. However, assuming the star-forming ring in NGC 7469 radiates with the average L_x_/L_5 GHz_ = 400 of starbursts, a X-ray luminosity L_x_ = 5.6 x 1O^41^ ergs s^-1^ is inferred. The ring contributes therefore to only about 4% of the integrated X-ray luminosity, L_x_ = 1.1 x 10^43^ ergs s^-1^. Pure active galactic nuclei (AGNs) are well differentiated from pure starbursts in the L-x_/L_H{alpha}_ ratio, independent of their absolute luminosity and activity level. For a given H{alpha} luminosity, AGNs produce 100 times more X-rays than pure starbursts do. The weak X-ray sources detected in some high-luminosity and ultraluminous infrared galaxies are characterized by X-ray to H{alpha} and to radio luminosity ratios L_x_/L_H{alpha}_ ~ 0.05 and L_x_/L_5 GHz_ ~ 20, respectively. These values are consistent with the ratios measured in nearly edge-on starbursts but about 100 times smaller than those of composite AGNs plus circumnuclear star-forming galaxies like NGC 1097 and NGC 7469. Subject headings: galaxies: active - galaxies: individual (NGC 1097, NGC 7469) - galaxies: Seyfert - galaxies: starburst - galaxies: structure - X-rays: galaxies
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