Bibcode
López-Corredoira, M.; Cabrera-Lavers, A.; Garzón, F.; Hammersley, P. L.
Referencia bibliográfica
Astronomy and Astrophysics, v.394, p.883-899 (2002)
Fecha de publicación:
11
2002
Revista
Número de citas
253
Número de citas referidas
228
Descripción
We have pursued two different methods to analyze the old stellar
population near the Galactic plane, using data from the 2MASS survey.
The first method is based on the isolation of the red clump giant
population in the color-magnitude diagrams and the inversion of its star
counts to obtain directly the density distribution along the line of
sight. The second method fits the parameters of a disc model to the star
counts in 820 regions. Results from both independent methods are
consistent with each other. The qualitative conclusions are that the
disc is well fitted by an exponential distribution in both the
galactocentric distance and height. There is not an abrupt cut-off in
the stellar disc (at least within R<15 kpc). There is a strong flare
(i.e. an increase of scale-height towards the outer Galaxy) which begins
well inside the solar circle, and hence there is a decrease of the
scale-height towards the inner Galaxy. Another notable feature is the
existence of a warp in the old stellar population whose amplitude is
coincident with the amplitude of the gas warp. It is shown for low
latitude stars (mean height: |z| ~ 300 pc) in the outer disc
(galactocentric radius R> 6 kpc) that: the scale-height in the solar
circle is hz(Rsun)=3.6x 10-2
Rsun, the scale-length of the surface density is
hR=0.42 Rsun and the scale-length of the space
density in the plane (i.e. including the effect of the flare) is H=0.25
Rsun. The variation of the scale-height due to the flare
follows roughly a law hz(R)~ hz(Rsun)
exp (R-Rsun)/([12-0.6R(kpc)] kpc) (for R<~ 15 kpc;
Rsun=7.9 kpc). The warp moves the mean position of the disc
to a height zw=1.2x 10-3 R(kpc)5.25sin
(phi +5o ) pc (for R<~ 13 kpc; Rsun=7.9 kpc).