IANIGLA   20881
INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
artículos
Título:
The distance to the Galactic center determined by OB stars
Autor/es:
BRANHAM, RICHARD L. JR.
Revista:
ASTROPHYSICS AND SPACE SCIENCE
Editorial:
SPRINGER
Referencias:
Lugar: Berlin; Año: 2014
ISSN:
0004-640X
Resumen:
The OB stars are concentrated near the Galactic
plane and should permit a determination of the distance
to the Galactic center. van Leeuwen?s new reduction of the
Hipparcos catalog provides, after 824 Gould belt stars have
been excluded, 6288 OB stars out to 1 kpc and Westin?s
compilation an additional 112 stars between 1 kpc and 3 kpc.
The reduction model involves 14 unknowns: the Oort A and
B constants, the distance to the Galactic center R0, 2 second order
partial derivatives, the 3 components of solar motion,
a K term, a first order partial derivative for motion perpendicular
to the Galactic plane, a second-order partial for acceleration
perpendicular to the plane, two terms for a possible
expansion of the OB stars, and a C constant. The
model is nonlinear, and the unknowns are calculated by use
the simplex algorithm for nonlinear adjustment applied to
14313 equations of condition, 12694 in proper motion and
1619 in radial velocity. Various solutions were tried: an L1
solution, a least squares solution with modest (2.7 %) trim
of the data, and two robust least squares solutions (biweight
and Welsch weighting) with more extreme trimming. The
Welsch solution seems to give the best results and calculates
a distance to the Galactic center 6.72 ± 0.39 kpc. Statistical
tests show that the data are homogeneous, that the reduction
model seems adequate and conforms with the assumptions
used in its derivation, and that the post-fit residuals are
random. Inclusion of more terms, such as streaming motion
induced by Galactic density waves, degrades the solution.