Katherine Vieira et al. 2007 The Astronomical Journal 134 1432 doi:10.1086/520813
Proper Motions in the Galactic Bulge: Plaut's Window
FREE ISSUEKatherine Vieira1, Dana I. Casetti-Dinescu1, René A. Méndez2, R. Michael Rich3, Terrence M. Girard1, Vladimir I. Korchagin1, William van Altena1, Steven R. Majewski4 and Sidney van den Bergh5
Show affiliationsA proper-motion study of a field of 20' × 20' inside Plaut's low-extinction window (l,b) = (0°, - 8°) 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 yr of epoch difference. Proper-motion errors are typically 1 mas yr-1, and field-dependent systematics are below 0.2 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 as a function of magnitude. 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 ± 0.11,2.91 ± 0.09) mas yr-1, which is in good agreement with previous results and indicates a velocity anisotropy consistent with either rotational broadening or triaxiality. A mean distance of 6.37
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 UBVRI photometry for the entire proper-motion sample of ~21,000 stars.
- Keywords
astrometry; catalogs; Galaxy: bulge; Galaxy: disk; stars: kinematics
- Dates
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Issue 4 (2007 October)
Received 2007 April 17, accepted for publication 2007 June 8
Published 2007 August 16
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Proper Motions in the Galactic Bulge: Plaut's Window
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