Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994aas...18510815m&link_type=abstract
American Astronomical Society, 185th AAS Meeting, #108.15; Bulletin of the American Astronomical Society, Vol. 26, p.1502
Astronomy and Astrophysics
Astronomy
Scientific paper
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 ( ~ 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 ~ 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 ~ 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 +/- 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.
Cecil Gerald
Morse Jon A.
Tsvetanov Zlatan
Wilson Andrew S.
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