Stellar Dynamics of Two AGNs

Abstract

We obtained long-slit spectroscopy of the LINER NGC 7331 and the Seyfert II NGC 5728 at the 4.2 m William Herschel Telescope with the ISIS spectrograph. We have determined the stellar Line of Sight Velocity Distribution (LOSVD), using the near-IR CaII triplet (~8500 Å), along the major axis of these two galaxies. The analysis of NGC 7331 shows (see Figure 1) that, in the radial range between 5″ and 20″, the LOSVD of the absorption lines has two components. This LOSVD can be decomposed (see Figure 2) into a fast-rotating component with v/σ > 3, and a slower rotating, retrograde component with v/σ ≈ 1–1.5. A two-dimensional bulge-disk decomposition of the near-infrared K-band image shows that the radial surface brightness profile of the counter-rotating component follows that of the bulge, while the fast-rotating component follows the disk. At the radius at which the disk starts to dominate, the isophotes change from being considerably boxy to being very disky. This makes NGC 7331 the first spiral galaxy known to have a boxy, fairly warm, counter-rotating component which is dominating the central regions.KeywordsAbsorption LineMajor AxisSpiral GalaxyHide StructureRadial RangeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.