A Distinct Structure Inside the Galactic Bar

Shogo Nishiyama(1), Tetsuya Nagata(2), Daisuke Baba(1), Yasuaki Haba(1), Ryota Kadowaki(1), Daisuke Kato(1), Mikio Kurita(1), Chie Nagashima(1), Takahiro Nagayama(2), Yuka Murai(2), Yasushi Nakajima(3), Motohide Tamura(3), Hidehiko Nakaya(4), Koji Sugitani(5), Takahiro Naoi(6), Noriyuki Matsunaga(7), Toshihiko Tanabe(7), Nobuhiko Kusakabe(8), Shuji Sato(1)


(1) Department of Astrophysics, Nagoya University, Nagoya, 464-8602, Japan
(2) Department of Astronomy, Kyoto University, Kyoto, 606-8502, Japan
(3) National Astronomical Observatory of Japan, Mitaka, 181-8588, Japan
(4) Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'ohoku Place, Hilo, HI 96720, U.S.A.
(5) Institute of Natural Science, Nagoya City University, Nagoya, 464-8602, Japan
(6) Department of Earth and Planetary Sciences The University of Tokyo, Tokyo, 113-0033, Japan
(7) Institute of Astronomy, School of Science, The University of Tokyo, Tokyo, 181-0015, Japan
(8) Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Tokyo, 184-8501, Japan

Paper: ApJL, accepted

Weblink: http://www.z.phys.nagoya-u.ac.jp/~shogo/papers/DistinctStructure.pdf

EPrint Server: astro-ph/0502058

Abstract:

We present the result of a near-infrared (J H KS) survey along the Galactic plane, -10.5 <= l <= 10.5 and b=+1 DEG, with the IRSF 1.4m telescope and the SIRIUS camera. KS vs. H-KS color-magnitude diagrams reveal a well-defined population of red clump (RC) stars whose apparent magnitude peak changes continuously along the Galactic plane, from KS=13.4 at l=-10 DEG to KS=12.2 at l=10 DEG after dereddening. This variation can be explained by the bar-like structure found in previous studies, but we find an additional inner structure at \mid l \mid< 4^o, where the longitude - apparent magnitude relation is distinct from the outer bar, and the apparent magnitude peak changes by only \thickapprox 0.1 mag over the central 8^o. The exact nature of this inner structure is as yet uncertain.

Preprints available from the authors at shogo@z.phys.nagoya-u.ac.jp , or the raw TeX (no figures) if you click here.

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