Formation of a two–dense–rings–pattern disk from the collapse of a cloud
E. Nagel
Instituto de Astronomía, Universidad Nacional Autónoma de México
E. Nagel: Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70–264, 04510 México, D. F., México (enagel@astroscu.unam.mx).
Received 2006 November 28 ]]> Accepted 2007 March 02
Resumen
En este artículo se estudia la formación de un disco, que resulta del colapso de una nube rotando rígidamente. El plano perpendicular al eje de la velocidad angular que contiene a la estrella es la superficie donde el material que cae de ambos lados se encuentra, formando así una estructura de choque de dos capas. El material chocado se mueve casi paralelo a este plano, siendo éste el material que forma el disco. Desarrollamos una simulación axi–simétrica e isoterma usando como condición inicial una aproximación balística para las trajectorias de las partículas localizadas en la vecindad de la estrella. La evolución dinámica de este material, incluyendo el material que continuamente se incorpora de la nube, lleva al disco a una configuración estacionaria que consta de dos anillos densos de momento angular específico constante que se encuentran en una posición kepleriana. Un rasgo como este puede cambiar el espectro de estos discos en etapas muy embebidas.
Abstract
In this paper, the formation of a disk resulting from the collapse of a rigidly–rotating cloud is studied. The plane perpendicular to the angular velocity axis that contains the star is the locus where materials falling from both sides face each other with the consequent formation of a double layer shock structure. The shocked material that moves almost parallel to this plane is the material that forms the disk. A hydrodynamical axisymmetric and isothermal simulation is developed using as initial condition a ballistic approximation for the trajectories of the particles located in the vicinity of the star. The dynamical evolution of this material, including the material that is continuously incorporated from the cloud, drives the disk to a stationary configuration composed of two dense rings with constant specific angular momentum that sit on Keplerian positions. A feature like this can change the spectra of disks in deeply embedded stages.
Key Words: Accretion, accretion disk—circumstellar matter—hydrodynamics—star: formation
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]]>Acknowledgement
I thank J. Cantó and A. Raga for their continued support and advice. The assistance of A. Raga in the numerical part of this research is gratefully acknowledged. I also thank J. Cantó for a critical reading of the original version of the paper.
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