# The Parsec‐Scale Accretion Disk in NGC 3393

 Title: The Parsec‐Scale Accretion Disk in NGC 3393 Author: Kondratko, Paul T.; Greenhill, Lincoln J.; Moran, James M. Note: Order does not necessarily reflect citation order of authors. Citation: Kondratko, Paul T., Lincoln J. Greenhill, and James M. Moran. 2008. “The Parsec‐Scale Accretion Disk in NGC 3393.” Astrophysical Journal 678 (1) (May): 87-95. doi:10.1086/586879. Full Text & Related Files: moran-parsec-scale.pdf (894.6Kb; PDF) Abstract: We present a Very Long Baseline Interferometry image of the water maser emission in the nuclear region of NGC 3393. The maser emission has a linear distribution oriented at a position angle of ~–34°, perpendicular to both the kiloparsec-scale radio jet and the axis of the narrow-line region. The position-velocity diagram displays a red-blue asymmetry about the systemic velocity and the estimated dynamical center, and is thus consistent with rotation. Assuming Keplerian rotation in an edge-on disk, we obtain an enclosed mass of ($$3.1 ± 0.2) × 10^7 M☉$$ within 0.36 ± 0.02 pc (1.48 ± 0.06 mas), which corresponds to a mean mass density of $$\sim10^{8.2} M☉ pc^{−3}$$. We also report the measurement with the Green Bank Telescope of a velocity drift, a manifestation of centripetal acceleration within the disk, of $$5 ± 1 km s^{−1} yr^{−1}$$ in the $$\sim3880 km s^{−1}$$ maser feature, which is most likely located along the line of sight to the dynamical center of the system. From the acceleration of this feature, we estimate a disk radius of 0.17 ± 0.02 pc, which is smaller than the inner disk radius (0.36 ± 0.02 pc) of emission that occurs along the midline (i.e., the line of nodes). The emission along the line of sight to the dynamical center evidently occurs much closer to the center than the emission from the disk midline, contrary to the situation in the archetypal maser systems NGC 4258 and NGC 1068. The outer radius of the disk as traced by the masers along the midline is about 1.5 pc. Published Version: doi:10.1086/586879 Other Sources: http://arxiv.org/abs/0801.4755 Terms of Use: This article is made available under the terms and conditions applicable to Other Posted Material, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#LAA Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:11596974 Downloads of this work: