Bibcode
Bellini, A.; Piotto, G.; Bedin, L. R.; Anderson, J.; Platais, I.; Momany, Y.; Moretti, A.; Milone, A. P.; Ortolani, S.
Bibliographical reference
Astronomy and Astrophysics, Volume 493, Issue 3, 2009, pp.959-978
Advertised on:
1
2009
Journal
Citations
106
Refereed citations
94
Description
Context: ω Centauri is the most well studied Galactic Globular
Cluster because of its numerous puzzling features: significant
dispersion in metallicity, multiple populations, triple main-sequence,
horizontal branch morphology, He-rich population(s), and extended
star-formation history. Intensive spectroscopic follow-up observing
campaigns targeting stars at different positions in the color-magnitude
diagram promises to clarify some of these peculiarities. Aims: To
be able to target cluster members reliably during spectroscopic surveys
and both spatial and radial distributions in the cluster outskirts
without including field stars, a high quality proper-motion catalog of
ω Cen and membership probability determination are required. The
only available wide field proper-motion catalog of ω Cen is
derived from photographic plates, and only for stars brighter than B~16.
Using ESO archive data, we create a new, CCD-based, proper-motion
catalog for this cluster, extending to B~20. Methods: We used
high precision astrometric software developed specifically for data
acquired by WFI@2.2m telescope and presented in the first paper of this
series. We demonstrated previously that a 7 mas astrometric precision
level can be achieved with this telescope and camera for well exposed
stars in a single exposure, assuming an empirical PSF and a local
transformation approach in measuring star displacements. Results:
We achieved a good cluster-field separation with a temporal base-line of
only four years. We corrected our photometry for sky-concentration
effects. We provide calibrated photometry for UBVR_CIC
wide-band data plus narrow-band filter data centered on Hα for
almost 360 000 stars. We confirm that the ω Cen metal-poor and
metal-rich components have the same proper motion, and demonstrate that
the metal-intermediate component in addition exhibits the same mean
motion as the other RGB stars. We provide membership probability
determinations for published ω Cen variable star catalogs. Conclusions: Our catalog extends the proper-motion measurements to
fainter than the cluster turn-off luminosity, and covers a wide area
(˜33 arcmin×33 arcmin) around the center of ω Cen. Our
catalog is electronically available to the astronomical community.
Based on archive observations with the MPI/ESO 2.2 m telescope, located
at La Silla and Paranal Observatory, Chile. Table 6 (catalog) is only
available in electronic form at the CDS via anonymous ftp to
cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/493/959