The Geometry of and Mass Accretion Rate through the Maser Accretion Disk in NGC 4258

摘要: A maximum likelihood analysis of the NGC 4258 maser positions and velocities reveals a ~2 sigma deviation from Keplerian motion in projected rotation curve high-velocity features, corresponding to ~9 km/s, or 0.8%, flattening LOS with respect over range masers. While there are number potential explanations for this flattening, we argue pure an inclination-warped disk based on ability model explain otherwise puzzling features system. radial gradient inclination 0.034 mas^{-1} is not only consistent observed curve, but it generates bowl along near edge that naturally explains narrow spread declinations systemic It also existence location apparently recurring flare amongst There no significant evidence non-Keplerian disk. An additional implication warp rises front obscures central engine at radius about 8.3 mas, 0.29 pc. By comparing X-ray column conditions radius, molecular-to-atomic transition occurs just beyond outermost 0.28 pc infer accretion rate \~10^{-4}alpha M_sun/yr, jet-dominated models Yuan et al. (2002). Our suggests most arises warped pc, emission truncated large radii predominantly as result phase originally proposed by Neufeld & Maloney (1995).