Modeling the Outflow in the Narrow-line Region of Markarian 573: Biconical Illumination of a Gaseous Disk

We present a study of the outflowing ionized gas in the resolved narrow-line region of the Seyfert 2 galaxy Mrk 573, and its interaction with an inner dust/gas disk, based on Hubble Space Telescope (HST) Wide Field Planetary Camera 2 and Space Telescope Imaging Spectrograph observations. From the spectroscopic and imaging information, we determined the fundamental geometry of the outflow and inner disk, via two modeling programs used to recreate the morphology of these regions imaged with HST. We also determined that the bicone of ionizing radiation from the active galactic nucleus intersects with the inner disk, illuminating a section of the disk including inner segments of spiral arms, fully seen through structure mapping, which appear to be outflowing and expanding. In addition, we see high velocities at projected distances of >=2'' (~700 pc) from the nucleus, which could be due to rotation or in situ acceleration of gas off the spiral arms. We find that the true half-opening angle of the ionizing bicone (53°) is much larger than the apparent half-opening angle (34°) due to the above geometry, which may apply to a number of other Seyferts as well.

Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.