MACHO Project Photometry of RR Lyrae Stars in the Sgr Dwarf Galaxy

Abstract

We report the discovery of 30 type a,b RR Lyrae (RRab) which are likely members of the Sagittarius (Sgr) dwarf galaxy. Accurate positions, periods, amplitudes and magnitudes are presented. Their distances are determined with respect to RRab in the Galactic bulge found also in the MACHO 1993 data. For R${}_{\odot }=8$ kpc, the mean distance to these stars is $D=22\pm 1$ kpc, smaller than previous determinations for this galaxy. This indicates that Sgr has an elongated main body extending for more than 10 kpc, which is inclined along the line of sight, with its northern part (in Galactic coordinates) closer to us. The size and shape of Sgr give clues about the past history of this galaxy. If the shape of Sgr follows the direction of its orbit, the observed spatial orientation suggests that Sgr is moving away from the Galactic plane. Also, Sgr stars may be the sources of some of the microlensing events seen towards the bulge.

arXiv comment15 pages including 4 PostScript figures, uses aaspp4.sty. Also available at http://wwwmacho.anu.edu.au/ or http://wwwmacho.mcmaster.ca/

References in corpus (3)

• The Disruption of the Sagittarius Dwarf Galaxy.
• The Optical Gravitational Lensing Experiment. Deep Photometry of the Sagittarius Dwarf Spheroidal Galaxy
• On the Dynamics of the Sagittarius Dwarf Galaxy

Cited by in corpus (31)

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• The Sagittarius Dwarf spheroidal Galaxy Survey (SDGS) II: The stellar content and constraints on the star formation history
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• The Sagittarius Dwarf Galaxy Survey (SDGS) I: CMDs, Reddening and Population Gradients. First evidences of a very metal poor population
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• The Large-Scale Extinction Map of the Galactic Bulge from the MACHO Project Photometry
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• Difference Image Analysis of Galactic Microlensing II. Microlensing Events
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• On the Oosterhoff dichotomy in the Galactic bulge: II. kinematical distribution
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• Current Status of the Microlensing Surveys
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