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Inclined Gas Disks in the Lenticular Seyfert Galaxy NGC 5252
We discuss the morphology and kinematics of the extended gas in the type2 Seyfert galaxy NGC 5252 based on Hubble Space Telescope (HST) WFPC2continuum and emission-line images (including a new [O iii] lambda5007image) and a ground-based Fabry-Perot (F-P) velocity map of the ionizedgas. The fine-scale morphology of the ionized gas in this galaxy's veryextended (~40 kpc) ionization bicone consists of a complex network offilamentary strands. The new WFPC2 [O iii] image also reveals moredetail in the circumnuclear (~3 kpc) gas disk than is seen in theHα + [N ii] image presented previously by Tsvetanov and coworkers.The F-P velocity map shows an obvious antisymmetry of the velocity fieldof the ionized gas across the nucleus. We conclude that there are threedynamical components to the extended gas in NGC 5252. Two of thesecomponents are gas disks aligned with the stellar disk, one rotatingwith the stars and the other counterrotating. The third component is thecircumnuclear gas disk seen in the HST observations and its extension tolarger scales; this disk has an inclination of ~40 deg and a kinematicmajor axis in P.A. ~ 90 deg-135 deg, some 80 deg-125 deg from the majoraxis of the stellar disk. This simple model of two inclined rotatingdisks, superposed along the line of sight, describes well the seeminglycomplex kinematics observed in the optical emission lines and the H i 21cm radio maps. The large misalignment between the second disk and thestellar disk suggests that the gas distribution, and possibly thenuclear activity, in NGC 5252 may have resulted from a galaxy mergerevent. The absence of significant radial motions, together with thewell-defined ionization cones, strongly suggests that the gas isphotoionized by a compact nuclear source rather than being ionized insitu by shock waves in a large-scale outflow. Based in part onobservations with the NASA ESA Hubble Space Telescope, obtained at theSpace Telescope Science Institute, which is operated by AURA, Inc.,under NASA contract NAS 5-26555.
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