Richard L. Branham, Jr.
Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales, C.C. 330, 5500 Mendoza, Argentina. (richardbranham1943@yahoo.com).
Received 2009 March 26
Accepted 2009 July 31
RESUMEN
]]> Para estudiar la cinemática de las gigantes K (clase de luminosidad III) se han utilizado los movimientos propios de la nueva reducción de van Leeuwen de los datos del catálogo de Hipparcos. En el estudio final, se consideraron 11,372 estrellas, de las cuales 880 tienen velocidades radiales conocidas. Mediante una programación semidefinida se obtuvieron valores para los parámetros cinemáticos (constantes de Oort) y simultáneamente, para los coeficientes del elipsoide de velocidades. Se obliga a que se cumpla la condición de que tanto la solución para la vecindad solar calculada a partir de los parámetros cinemáticos como la obtenida a partir del elipsoide de velocidades sean iguales. La solución nos da valores de 21.83 ± 0.26 km s–1 para el movimiento solar, y A = 13.08 ± 1.72 km s–1 kpc–1 y B = –10.21 ± 1.47 km s–1 kpc–1 para las constantes de Oort, lo cual implica una velocidad local de rotación de 197.94 ±44.73 km s–1 si suponemos una distancia al centro galáctico de 8.2 ± 1.1 kpc. Para las dispersiones de velocidades obtenemos σx = 50.58 ± 0.99 km s–1, σy = 42.42 ± 1.13 km s–1 y σz = 32.92 ± 0.56 km s–1, con una desviación del vértice de –7.°53 ± 3.°97.
ABSTRACT
To study the kinematics of the K giant stars (luminosity class III) use is made of proper motions taken from van Leeuwen's new reduction of the Hipparcos catalog. 11,372 stars, of which 880 have radial velocities, were used in the final study. Semi–definite programming solves for the kinematical parameters such as the Oort constants and simultaneously for the coefficients of the velocity ellipsoid. The condition that both the solution for the solar velocity calculated from the kinematical parameters and from the velocity ellipsoid calculation be the same is enforced. The solution gives: solar velocity of 21.83±0.26 km s–1; Oort's constant's, in units of km s–1 kpc–1, A = 13.08 ± 1.72 and B = –10.21 ± 1.47, implying a rotational velocity of 197.94 ± 44.73 km s–1 if we take the distance to the Galactic center as 8.2±1.1 kpc; velocity dispersions, in units of km s–1, of: σx = 50.58±0.99, σy = 42.42 ± 1.13, σz = 32.92 ± 0.56 with a vertex deviation of –7.°53 ± 3.°97.
Key Words: Galaxy: kinematics and dynamics — methods: numerical.
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