WFPC-2 Imaging of a Spiral Gas Disk Surrounding the Nucleus of NGC~5252
Session 108 -- Seyfert Galaxies
Display presentation, Thursday, 12, 1995, 9:20am - 6:30pm

## [108.15] WFPC-2 Imaging of a Spiral Gas Disk Surrounding the Nucleus of NGC~5252

J.A. Morse (STScI), Z. Tsvetanov (JHU), G. Cecil (UNC-CH), A.S. Wilson (UMd)

We present HST/WFPC-2 images of the nuclear region of the Seyfert 2 galaxy NGC~5252 that reveal a spectacular morphology of the circumnuclear line-emitting gas. First, the nucleus is embedded in what appears to be a small scale ($\sim 1''$, 450 pc at 92 Mpc distance assuming $H_0 = 75$ km s$^{-1}$ Mpc$^{-1}$) nuclear disk of ionized gas seen almost edge-on. Three bright peaks separated by $\sim 0.''3$ are arranged in a straight line roughly along the galaxy major axis. The peaks are aligned just outside one of the edges of the large-scale ionization cone, perhaps even determining it. Second, the ionized circumnuclear gas within $\sim 4''$ of the nucleus extends from the small-scale disk and wraps sharply into a distinct spiral morphology, very similar to that shown by the gas disk in the M87 nucleus.

We also present a two-dimensional kinematic map of the remarkable, large-scale ionization bi-cone in this galaxy obtained on the CTIO 4-m telescope with the Rutgers/CTIO Fabry-Perot spectrometer with 30 km s$^{-1}$ FWHM velocity resolution. Broad, high-velocity emission is seen near the nucleus over scales of the spiral structure that may indicate a rapidly rotating disk. On larger scales, the gas along the galaxy major axis is counter-rotating with respect to the stellar component. The gas along the ionization cone axis oscillates between $\pm 150$ km s$^{-1}$ of the systemic velocity of the galaxy, and this saw-toothed velocity field has a mirror symmetry about the nucleus. We also observe velocity gradients perpendicular to the cone axis in the extended, arcuate shells. We plot the gaseous excitation and density as a function of distance from the nucleus along the cone axis as seen in a long-slit spectrum and discuss the ionized gas distribution and emission-line characteristics in the context of the unified scheme for AGNs.

This research is supported by NASA grants to STScI and JHU.