Globular clusters: Absolute Proper Motions and Galactic Orbitsстатья
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Дата последнего поиска статьи во внешних источниках: 10 августа 2018 г.
Аннотация:We cross-match objects from several different astronomical
catalogs to determine the absolute proper motions of stars within
the 30-arcmin radius fields of 115 Milky-Way globular clusters
with the accuracy of 1--2 mas/yr. The proper motions are based on
positional data recovered from the USNO-B1, 2MASS, URAT1,
ALLWISE, UCAC5, and GAIA DR1 surveys with up to 10 positions
spanning an epoch difference of up to 65 years, and reduced
to GAIA DR1 TGAS frame using UCAC5 as the reference catalog.
Cluster members are photometrically identified by selecting
horizontal- and red-giant branch stars on color-magnitude
diagrams, and the mean absolute proper motions of the clusters
with a typical formal error of 0.4 mas/yr are computed by
averaging the proper motions of selected members. The inferred
absolute proper motions of clusters are combined with available
radial-velocity data and heliocentric distance estimates to
compute the cluster orbits in terms of the Galactic potential
models based on Miyamoto and Nagai disk, Hernquist spheroid, and
modified isothermal dark-matter halo (axisymmetric model without a
bar) and the same model + rotating Ferre's bar (non-axisymmetric).
Five distant clusters have higher-than-escape velocities, most
likely due to large errors of computed transversal velocities,
whereas the computed orbits of all other clusters remain bound to
the Galaxy. Unlike previously published results, we find the bar
to affect substantially the orbits of most of the clusters, even
those at large Galactocentric distances, bringing appreciable
chaotization, especially in the portions of the orbits close to
the Galactic center, and stretching out the orbits of some of the
thick-disk clusters.