A Distinct Structure inside the Galactic Bar

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Published 2005 February 15 © 2005. The American Astronomical Society. All rights reserved. Printed in U.S.A.
, , Citation Shogo Nishiyama et al 2005 ApJ 621 L105 DOI 10.1086/429291

1538-4357/621/2/L105

Abstract

We present the result of a near-infrared (JHKs) survey along the Galactic plane, -10fdg5 ≤ l ≤ 10fdg5 and b = +1°, with the IRSF 1.4 m telescope and the SIRIUS camera. Ks versus H - Ks color-magnitude diagrams reveal a well-defined population of red clump stars whose apparent magnitude peak changes continuously along the Galactic plane, from Ks = 13.4 at l = -10° to Ks = 12.2 at l = 10° after dereddening. This variation can be explained by the barlike structure found in previous studies, but we find an additional inner structure at ∣ l ∣ ≲ 4°, where the longitude-apparent magnitude relation is distinct from the outer bar and where the apparent magnitude peak changes by only ≈0.1 mag over the central 8°. The exact nature of this inner structure is as yet uncertain.

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10.1086/429291