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Modelling the Galactic Bar using Red Clump Stars

Published online by Cambridge University Press:  12 April 2016

K. Z. Stanek ,
M. Mateo ,
A. Udalski ,
M. Szymański ,
J. Kałuzny ,
M. Kubiak  and
W. Krzemiński
K. Z. Stanek
Affiliation:
Princeton University Observatory, PrincetonNJ 08544–1001
M. Mateo
Affiliation:
Department of Astronomy, University of Michigan, 821 Dennison Bldg., Ann Arbor, MI 48109–1090
A. Udalski
Affiliation:
Warsaw University Observatory, AL Ujazdowskie 4, 00–478 Warszawa, Poland
M. Szymański
Affiliation:
Warsaw University Observatory, AL Ujazdowskie 4, 00–478 Warszawa, Poland
J. Kałuzny
Affiliation:
Warsaw University Observatory, AL Ujazdowskie 4, 00–478 Warszawa, Poland
M. Kubiak
Affiliation:
Warsaw University Observatory, AL Ujazdowskie 4, 00–478 Warszawa, Poland
W. Krzemiński
Affiliation:
Carnegie Observatories, Las Campanas Observatory, Casilla 601, La Serena, Chile

Abstract

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The color-magnitude diagrams of ~ 1 × 106 stars obtained for 19 fields towards the Galactic bulge with the OGLE project reveal a well-defined population of bulge red clump stars. We found that the distributions of the extinction-adjusted apparent magnitudes of red clump stars in fields lying at ι = ±5° in galactic longitude differ by ∼ 0.4 mag. A plausible explanation of this observed difference in the luminosity distribution is that the Galactic bulge is a triaxial structure, or a bar, which is inclined to the line of sight by no more than 45°. The part of the bar at the positive galactic longitude is closer to us. Work is now under way to model the Galactic bar by fitting the observed luminosity functions in the red clump region for various fields. Preliminary results indicate that the angle of the inclination of the bar to the line of sight can be as small as ∼ 20°. Gravitational microlensing can provide us with additional constraints on the structure of the Galactic bar.

Type
Part IX. The Galaxy as a Barred Spiral
Information
International Astronomical Union Colloquium , Volume 157: Barred Galaxies , 1996 , pp. 545 - 548
Copyright
Copyright © Astronomical Society of the Pacific 1996

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