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From: Shogo NISHIYAMA  shogo@z.phys.nagoya-u.ac.jp 
To: gcnews@aoc.nrao.edu
Subject: submit exlaw.tex ApJ, Feb 2006, in press

%astro-ph/0601174

\documentclass[12pt,preprint]{aastex}

\begin{document}

\title{Interstellar Extinction Law in the $J, H$, and $K_S$ Bands\\
toward the Galactic Center}

\author{Shogo Nishiyama, 
Tetsuya Nagata,
Nobuhiko Kusakabe, 
Noriyuki Matsunaga, 
Takahiro Naoi,
Daisuke Kato,
Chie Nagashima, 
Koji Sugitani,
Motohide Tamura,
Toshihiko Tanab$\mathrm{\acute{e},
and Shuji Sato
}

\begin{abstract}
We have determined the ratios of total to selective extinction 
in the near-infrared bands ($J, H, K_S$)
toward the Galactic center from the observations of the region 
$\mid l \mid \la 2\fdg0$ and $0\fdg5 \la \mid b \mid \la 1\fdg0$
with the IRSF telescope and the SIRIUS camera. 
Using the positions of red clump stars in color-magnitude diagrams
as a tracer of the extinction and reddening,
we determine the average of the ratios of total to selective extinction to be
$A_{K_S}/E_{H-K_S} = 1.44\pm0.01$,
$A_{K_S}/E_{J-K_S} = 0.494\pm0.006$, and
$A_{H}/E_{J-H} =1.42\pm0.02$,
which are significantly smaller than 
those obtained in previous studies.  
>From these ratios, we estimate that
$ A_{J} : A_{H} : A_{K_S} = 1 : 0.573 \pm 0.009 : 0.331 \pm 0.004 $
and $E_{J-H}/E_{H-K_S} = 1.72 \pm 0.04$,  
and we find that the power law 
$A_{\lambda} \propto \lambda^{-1.99 \pm 0.02}$
is a good approximation over these wavelengths.
Moreover, we find a small variation in $A_{K_S}/E_{H-K_S}$ 
across our survey.
This suggests that the infrared extinction law changes 
from one line of sight to another,
and the so-called ``universality'' does not necessarily hold 
in the infrared wavelengths.
\end{abstract}

\end{document}