Héctor Velázquez
Instituto de Astronomía, UNAM, Apdo. Postal 877, 22860 Ensenada, B. C., México (hmv@astrosen.unam.mx).
Received, 2003 June 26
Accepted 2005 April 4
]]> RESUMEN
Se ha realizado una serie de simulaciones de N-cuerpos de galaxias espirales para estudiar los efectos del calentamiento del disco como resultado de los encuentros de dos cuerpos. Se han cuantificado los coeficientes de difusión y los tiempos de relajamiento en las direcciones radial y vertical en un radio de referencia. Las partículas del disco juegan un papel marginal en el calentamiento vertical de disco, mientras que pueden contribuir de manera importante al calentamiento radial siempre que el halo no este pobremente muestreado; de otra manera, el calentamiento radial y vertical estará dominado por encuentros entre partículas del disco y el halo. Además, se encuentra que el disco es más eficientemente calentado en la dirección radial que en la vertical a un radio dado. Finalmente, se ha derivado una expresión para estimar, a priori, el número de partículas del halo (dentro de un radio de referencia) requeridas para mantener el calentamiento del disco a un nivel deseado.
ABSTRACT
A set of N-body simulations of disk galaxies has been carried out to study the heating effects on the disk component, resulting from two-body encounters. We have quantified the diffusion coefficients and relaxation times in the radial and vertical directions at a given reference radius. Disk self-heating plays a marginal role in the vertical heating of the disk while it has an important contribution to the radial heating whenever the halo is not poorly sampled; otherwise, both the radial and vertical heating will be dominated by disk-halo particle encounters. Also, it is found that the disk is more efficiently heated in the radial direction than in the vertical one at a given radius. Finally, an expression has been derived to estimate, a priori, the number of halo particles (inside the reference radius) required to maintain the heating of the disc within a desired level.
Key Words: Galaxies: Kinematics and dynamics — Methods: N-body simulations — Methods: Numerical.
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ACKNOWLEDGMENTS
]]> I thank Luis Aguilar and an anonymous referee for some helpful suggestions to improve the present work. This work was supported by CONACyT under grant 27678-E.
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