Hypersonic acceleration and turbulence of H2O masters in W49N

Abstract

view Abstract Citations (65) References (44) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Hypersonic Acceleration and Turbulence of H 2O Masers in W49N Gwinn, C. R. Abstract Velocity turbulence and hypersonic acceleration of H2O maser features appear in their distributions in position and velocity. These conclusions are based on five epochs of astrometric Very Long Baseline Interferometry (VLBI) observations of W49N, particulary on the fourth epoch, when more than 250 features were detected. Correlation functions indicate that physical masers features have sizes of 1 AU and velocity scales of 0.5 km/s. Between 1 and 300 AU, maser features show power-law correlation functions suggestive of velocity turbulence. At scales of 300 AU, masers are organized into arcs: associations of features oriented perpendicular to the direction of outflow. Velocities of features, including proper motion as well as Doppler velocity, show a minimum of about 20 km/s. The high Doppler velocities of some features, long observed spectroscopically, represent high physical velocities. High-velocity features lie at the periphery of the maser cluster. The association of high- and low-velocity features on scale of 300 AU, much less than 104 AU diameter of the cluster, suggests that high-velocity features are accelerated in situ. These observations can be understood in a picture where an energetic stellar wind strikes ambient material to produce masers behind shocks. Fluid instabilities in the shocked material, such as the instability of C-shocks discovered by Wardle, may then produce the strong turbulence observed between masers. Ram pressure from this wind could accelerate high-velocity features to the observed hypersonic velocities, as suggested by Strelnitskii & Sunyaev. Publication: The Astrophysical Journal Pub Date: July 1994 DOI: 10.1086/174315 Bibcode: 1994ApJ...429..241G Keywords: Astronomy; Hypersonic Wakes; Turbulent Flow; Water Masers; Coherent Electromagnetic Radiation; Doppler Effect; Flow Velocity; Velocity Distribution; Very Long Base Interferometry; Astrophysics; ASTROMETRY; ISM: INDIVIDUAL ALPHANUMERIC: W49; ISM: KINEMATICS AND DYNAMICS; TURBULENCE full text sources ADS | data products SIMBAD (2)