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THE VERTICAL STELLAR KINEMATICS IN FACE-ON BARRED GALAXIES: ESTIMATING THE AGES OF BARS
 

Summary: THE VERTICAL STELLAR KINEMATICS IN FACE-ON BARRED GALAXIES:
ESTIMATING THE AGES OF BARS
D. A. Gadotti1
and R. E. de Souza
Departamento de Astronomia, Universidade de Sa~o Paulo, Rua do Mata~o, 1226 Cidade Universitaria CEP,
05508-090, Sa~o Paulo SP, Brazil; dimitri@astro.iag.usp.br, ronaldo@astro.iag.usp.br
Received 2004 September 17; accepted 2005 April 28
ABSTRACT
In order to perform a detailed study of the stellar kinematics in the vertical axis of bars, we obtained high signal-
to-noise spectra along the major and minor axes of the bars in a sample of 14 face-on galaxies and used them to
determine the line-of-sight stellar velocity distribution, parameterized as a Gauss-Hermite series. With these data,
we developed a diagnostic tool that allows one to distinguish between recently formed and evolved bars, as well as
to estimate their ages, assuming that bars form in vertically thin disks that are recognizable by low values for the
vertical velocity dispersion z. Through N-body realizations of bar unstable disk galaxies we were also able to
check the timescales involved in the processes that give bars an important vertical structure. We show that z in
evolved bars is roughly 100 km sĄ1
, which translates to a height scale of about 1.4 kpc, giving support to scenarios
in which bulges form through disk material. Furthermore, the bars in our numerical simulations have values for z
generally smaller than 50 km sĄ1
, even after evolving for 2 Gyr, suggesting that a slow process is responsible for

  

Source: Alexei, Dimitri - European Southern Observatory

 

Collections: Physics