L. Zaninetti
Dipartimento di Fisica Generale, Università degli Studi di Torino, Via Pietro Giuria 1, 10125 Torino, Italy (zaninetti@ph.unito.it)
Received 2006 March 2
Accepted 2006 October 10
RESUMEN
]]> Se sugieren 5 métodos analíticos para encontrar una ley que caracterice el decremento de la velocidad a lo largo del chorro. Los 2 primeros son modelos simples que examinan la variación de la velocidad en presencia de la resistencia de Newton o de Stoke. Se resuelve la ecuación que representa la conservación del momento a lo largo de un sector piramidal desde un punto de vista analítico (tercer modelo). La aplicación de la conservación del flujo del momento total nos permite deducir la velocidad de la galaxia como función del tiempo para velocidades clásicas (cuarto modelo) y para velocidades relativistas (quinto modelo). La variación de la velocidad a lo largo del chorro combinada con una adecuada composición de la velocidad de precesión del chorro, con la velocidad rotacional de la galaxia y con la dispersión de velocidades de la galaxia en el cúmulo nos permite trazar el patrón geométrico de las fuentes de radio con cabeza y cola. La aplicación de la teoría/código desarrollado a las radiogalaxias NGC1265, NGC4061, NGC326, y Cygnus A nos da una dispersión de velocidades aproximada de la galaxia central en la dirección perpendicular al chorro. Introducimos una transición desde las galaxias cabeza–cola a las clásicas radiogalaxias dobles como función del incremento de la potencia mecánica del chorro.
ABSTRACT
In order to find a law characterising the decrease of velocity along a jet, five analytical methods are suggested. The first two simple models examine the variation of velocity in the presence of Newton's or Stoke's resistance. The equation that represents the conservation of the momentum along a pyramidal sector is solved from an analytical point of view (third model). The application of the conservation of the total momentum flux allows us to deduce the velocity of the galaxy as a function of time for classical velocities (fourth model) and relativistic velocities (fifth model). The variation of velocity along the jet combined with an adequate composition of jet precession velocity, rotational velocity of the galaxy, and galaxy velocity dispersion in the cluster allows us to trace the geometrical pattern of the head–tail radio sources. Application of the developed theory/code to the radio galaxies NGC1265, NGC4061, NGC326, and Cygnus A gives the central galaxy's approximate dispersion velocities in the direction perpendicular to the jet. A transition from head–tails to classical double radio galaxies as a function of the increasing jet's mechanical power is introduced.
Key Words: GALAXIES: JETS RADIO — CONTINUUM: GALAXIES
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