Inclined gas disks in the lenticular Seyfert galaxy NGC 5252

We discuss the morphology and kinematics of the extended gas in the type 2 Seyfert galaxy NGC 5252 based on Hubble Space Telescope (HST) WFPC2 continu um and emission-line images (including a new [O III] lambda 5007 image) and a ground-based Fabry-Perot (F-P) velocity map of the ionized gas. The fine -scale morphology of the ionized gas in this galaxy's very extended (simila r to 40 kpc) ionization bicone consists of a complex network of filamentary strands. The new WFPC2 [O III] image also reveals more detail in the circu mnuclear (similar to 3 kpc) gas disk than is seen in the H alpha + [N II] i mage presented previously by Tsvetanov and coworkers. The F-P velocity map shows an obvious antisymmetry of the velocity held of the ionized gas acros s the nucleus. We conclude that there are three dynamical components to the extended gas in NGC 5252. Two of these components are gas disks aligned wi th the stellar disk, one rotating with the stars and the other counterrotat ing. The third component is the circumnuclear gas disk seen in the HST obse rvations and its extension to larger scales; this disk has an inclination o f similar to 40 degrees and a kinematic major axis in P.A. similar to 90 de grees-135 degrees, some 80 degrees-125 degrees from the major axis of the s tellar disk. This simple model of two inclined rotating disks, superposed a long the line of sight, describes well the seemingly complex kinematics obs erved in the optical emission lines and the H I 21 cm radio maps. The large misalignment between the second disk and the stellar disk suggests that th e gas distribution, and possibly the nuclear activity, in NGC 5252 may have resulted from a galaxy merger event. The absence of significant radial mot ions, together with the well-defined ionization cones, strongly suggests th at the gas is photoionized by a compact nuclear source rather than being io nized in situ by shock waves in a large-scale outflow.