Concerning the Distance to the Center of the Milky Way and Its Structure
D. Majaess
Saint Mary's University, Halifax, Nova Scotia, Canada The Abbey Ridge Observatory, Stillwater Lake, Nova Scotia, Canada
e-mail: [email protected]
Received: January 20, 2010
ABSTRACT
The distance to the Galactic center inferred from OGLE RR Lyr variables
observed in the direction of the bulge is
R0=8.1±0.6 kpc. An accurate determination of
R0 is hindered by countless effects that include an
ambiguous extinction law, a bias for smaller values of R0
because of a preferential sampling of variable stars toward the near side
of the bulge owing to extinction, and an uncertainty in characterizing how
a mean distance to the group of variable stars relates to
R0. A VI-based period-reddening relation for
RR Lyr variables is derived to map extinction throughout the
bulge. The reddening inferred from RR Lyr variables in the Galactic
bulge, LMC, SMC, and IC 1613 match that established from OGLE red
clump giants and classical Cepheids. RR Lyr variables obey a
period-color (VI) relation that is relatively insensitive to
metallicity. Edge-on and face-on illustrations of the Milky Way are
constructed by mapping the bulge RR Lyr variables in tandem with
cataloged red clump giants, globular clusters, planetary nebulae, classical
Cepheids, young open clusters, HII regions, and molecular clouds. The
sample of RR Lyr variables do not trace a prominent Galactic bar or
triaxial bulge oriented at φ≅25°.
Key words:
Stars: distances - Galaxy: center - Galaxy: structure
Full article text (PDF)
back
