Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-04-19
Astrophys.J. 629 (2005) 719-738
Astronomy and Astrophysics
Astrophysics
30 pages, 23 figures. Accepted for publication in ApJ. Full-resolution version (with color figure) available at http://www.a
Scientific paper
10.1086/431421
A maximum likelihood analysis of the NGC 4258 maser positions and velocities reveals a ~2 sigma deviation from Keplerian motion in the projected rotation curve of the high-velocity features, corresponding to a ~9 km/s, or 0.8%, flattening of the LOS velocities with respect to Keplerian motion over the range of the high-velocity masers. While there are a number of potential explanations for this flattening, we argue for pure Keplerian rotation in an inclination-warped disk based on the ability of this model to explain a number of otherwise puzzling features of the system. A radial gradient in the disk inclination of 0.034 mas^{-1} is not only consistent with the observed rotation curve, but it generates a bowl along the near edge of the disk that naturally explains the otherwise puzzling narrow spread in the declinations of the systemic masers. It also explains the existence and location of an apparently recurring flare amongst the systemic masers. There is no significant evidence for non-Keplerian rotation in the inclination-warped disk. An additional implication of the inclination warp is that the disk rises in front of and obscures the central engine at a disk radius of about 8.3 mas, or 0.29 pc. By comparing the observed X-ray column to conditions in the disk at this radius, we argue that the molecular-to-atomic transition occurs just beyond the outermost maser at 0.28 pc and from this we infer an accretion rate of \~10^{-4}alpha M_sun/yr, consistent with the jet-dominated accretion models of Yuan et al. (2002). Our model suggests that most of the observed X-ray column arises in the warped accretion disk at 0.29 pc, and that the maser emission is truncated at large radii predominantly as a result of the molecular-to-atomic phase transition originally proposed by Neufeld & Maloney (1995).
Greenhill Lincoln J.
Herrnstein James Rezso
Moran James Michael
Trotter Adam S.
No associations
LandOfFree
The Geometry of and Mass Accretion Rate through the Maser Accretion Disk in NGC 4258 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Geometry of and Mass Accretion Rate through the Maser Accretion Disk in NGC 4258, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Geometry of and Mass Accretion Rate through the Maser Accretion Disk in NGC 4258 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-40294