Measurement of the epicycle frequency in the Galactic disc and initial velocities of open clusters


Autoria(s): LEPINE, J. R. D.; DIAS, Wilton S.; MISHUROV, Yu.
Contribuinte(s)

UNIVERSIDADE DE SÃO PAULO

Data(s)

19/10/2012

19/10/2012

2008

Resumo

A new method to measure the epicycle frequency kappa in the Galactic disc is presented. We make use of the large data base on open clusters completed by our group to derive the observed velocity vector (amplitude and direction) of the clusters in the Galactic plane. In the epicycle approximation, this velocity is equal to the circular velocity given by the rotation curve, plus a residual or perturbation velocity, of which the direction rotates as a function of time with the frequency kappa. Due to the non-random direction of the perturbation velocity at the birth time of the clusters, a plot of the present-day direction angle of this velocity as a function of the age of the clusters reveals systematic trends from which the epicycle frequency can be obtained. Our analysis considers that the Galactic potential is mainly axis-symmetric, or in other words, that the effect of the spiral arms on the Galactic orbits is small; in this sense, our results do not depend on any specific model of the spiral structure. The values of kappa that we obtain provide constraints on the rotation velocity of the in particular, V(0) is found to be 230 +/- 15 km s(-1) even if the scale (R(0) = 7.5 kpc) of the Galaxy is adopted. The measured kappa at the solar radius is 43 +/- 5 km s(-1) kpc(-1). The distribution of initial velocities of open clusters is discussed.

Identificador

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, v.386, n.4, p.2081-2090, 2008

0035-8711

http://producao.usp.br/handle/BDPI/27030

10.1111/j.1365-2966.2008.13168.x

http://dx.doi.org/10.1111/j.1365-2966.2008.13168.x

Idioma(s)

eng

Publicador

WILEY-BLACKWELL

Relação

Monthly Notices of the Royal Astronomical Society

Direitos

restrictedAccess

Copyright WILEY-BLACKWELL

Palavras-Chave #Galaxy : kinematics and dynamics #open clusters and associations : general #HIPPARCOS PROPER MOTIONS #ROTATION CURVE #SPIRAL STRUCTURE #YOUNG STARS #MILKY-WAY #GALAXY #KINEMATICS #DISTANCE #CONSTANTS #CATALOG #Astronomy & Astrophysics
Tipo

article

original article

publishedVersion