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Proper motions in the Galactic bulge: Plaut's window

Published online by Cambridge University Press:  01 July 2007

Katherine Vieira ,
Dana Cassetti-Dinescu ,
René A. Méndez ,
R. Michael Rich ,
Terrence M. Girard ,
Vladimir I. Korchagin ,
William van Altena ,
Steven R. Majewski  and
Sidney van den Bergh
Katherine Vieira
Affiliation:
Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 06520, USA email: vieira@astro.yale.edu, dana@astro.yale.edu, girard@astro.yale.edu, vik@astro.yale.edu, vanalten@astro.yale.edu
Dana Cassetti-Dinescu
Affiliation:
Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 06520, USA email: vieira@astro.yale.edu, dana@astro.yale.edu, girard@astro.yale.edu, vik@astro.yale.edu, vanalten@astro.yale.edu
René A. Méndez
Affiliation:
Depto. de Astronomia, Universidad de Chile, Casilla 36-D, Santiago, Chile email: rmendez@das.uchile.cl
R. Michael Rich
Affiliation:
University of California, 8979 Math Sciences, Los Angeles, CA 90095-1562, USA email: rmr@astro.ucla.edu
Terrence M. Girard
Affiliation:
Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 06520, USA email: vieira@astro.yale.edu, dana@astro.yale.edu, girard@astro.yale.edu, vik@astro.yale.edu, vanalten@astro.yale.edu
Vladimir I. Korchagin
Affiliation:
Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 06520, USA email: vieira@astro.yale.edu, dana@astro.yale.edu, girard@astro.yale.edu, vik@astro.yale.edu, vanalten@astro.yale.edu
William van Altena
Affiliation:
Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 06520, USA email: vieira@astro.yale.edu, dana@astro.yale.edu, girard@astro.yale.edu, vik@astro.yale.edu, vanalten@astro.yale.edu
Steven R. Majewski
Affiliation:
University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325, USA email: srm4n@didjeridu.astro.virginia.edu
Sidney van den Bergh
Affiliation:
Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada email: sidney.vandenBergh@nrc-cnrc.gc.ca
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Abstract

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A proper motion study of a field of 20′ × 20′ inside Plaut's low extinction window (l,b)=(0o, −8o), has been completed. Relative proper motions and photographic BV photometry have been derived for ~ 21,000 stars reaching to V ~ 20.5 mag, based on the astrometric reduction of 43 photographic plates, spanning over 21 years of epoch difference. Proper motion errors are typically 1 mas yr−1. Cross-referencing with the 2MASS catalog yielded a sample of ~ 8700 stars, from which predominantly disk and bulge subsamples were selected photometrically from the JH color-magnitude diagram. The two samples exhibited different proper-motion distributions, with the disk displaying the expected reflex solar motion. Galactic rotation was also detected for stars between ~2 and ~3 kpc from us. The bulge sample, represented by red giants, has an intrinsic proper motion dispersion of (σl, σb) = (3.39, 2.91)±(0.11, 0.09) mas yr−1, which is in good agreement with previous results. A mean distance of kpc has been estimated for the bulge sample, based on the observed K magnitude of the horizontal branch red clump. The metallicity [M/H] distribution was also obtained for a subsample of 60 bulge giants stars, based on calibrated photometric indices. The observed [M/H] shows a peak value at [M/H] ~ −0.1 with an extended metal poor tail and around 30% of the stars with supersolar metallicity. No change in proper motion dispersion was observed as a function of [M/H]. We are currently in the process of obtaining CCD UBV RI photometry for the entire proper-motion sample of ~ 21,000 stars.

Keywords

astrometry — stars: kinematics — Galaxy: bulge — Galaxy: disk — catalogs
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S245: Formation and Evolution of Galaxy Bulges , July 2007 , pp. 351 - 354
Copyright
Copyright © International Astronomical Union 2008

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