W. J. Maciel, T. S. Rodrigues, and R. D. D. Costa
Instituto de Astronomia, Geofísica e Ciencias Atmosféricas Universidade de São Paulo, Rua do Matão 1226, CEP 05508–090, São Paulo SP, Brazil (maciel, tsrodrigues, roberto@astro.iag.usp.br).
Received 2011 July 01
Accepted 2011 August 11
]]> RESUMEN
Se determina la distribución de edades de las estrellas centrales de nebulosas planetarias (CSPN) utilizando dos métodos basados en sus propiedades cinemáticas. En primer lugar, se comparan las velocidades de rotación de las nebulosas esperadas a partir de sus distancias galactocéntricas con los valores predichos por la curva de rotación, y las diferencias encontradas se atribuyen a las distintas edades de las estrellas evolucionadas. Se usa la relación entre las edades y la dispersion de velocidades del relevamiento Geneva–Copenhagen para obtener la distribución de edades. En segundo lugar, se determinan las componentes U, V, W de las velocidades de las estrellas, y se usan las relaciones edad–dispersión de velocidades para inferir la distribución de edades. Hemos aplicado estos métodos a dos muestras de nebulosas planetarias en nuestra galaxia. Los resultados son similares para ambas, y muestran que la distribución de edades de las CSPN estó concentrada en edades menores que 5 giga–años, y que tiene un pico entre 1 y 3 giga–años.
ABSTRACT
The age distribution of the central stars of planetary nebulae (CSPN) is estimated using two methods based on their kinematic properties. First, the expected rotation velocities of the nebulae at their Galactocentric distances are compared with the predicted values from the rotation curve, and the differences are attributed to the different ages of the evolved stars. Adopting the relation between the ages and the velocity dispersions determined by the Geneva–Copenhagen survey, the age distribution can be derived. Second, the U, V, W, velocity components of the stars are determined, and the corresponding age–velocity dispersion relations are used to infer the age distribution. These methods have been applied to two samples of PN in the Galaxy. The results are similar for both samples, and show that the age distribution of the PN central stars concentrates at ages lower than 5 Gyr, peaking at about 1 to 3 Gyr.
Key Words: planetary nebulae: general — stars: AGB and Post–AGB — stars: fundamental parameters — stars: general.
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ACKNOWLEDGMENTS
]]> We thank Dr. R. Branham, Jr., for some interesting comments on an earlier version of this paper. This work was partly supported by FAPESP and CNPq.
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