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 Matsu2009.tex MNRAS, Nov 2009, Volume 399, pp. 1709-1729
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% arXiv:0907.2761
\documentclass[useAMS,usenatbib,usegraphicx]{mn2e}
\usepackage{times}

\title[Miras towards the Galactic Centre]
{A near-infrared survey of Miras and the distance to the Galactic Centre}
\author[N. Matsunaga et al.]
{Noriyuki
Matsunaga,$^{1,2}$\thanks{E-mail:matsunaga@ioa.s.u-tokyo.ac.jp}\thanks{Research
Fellow of the Japan Society for the Promotion of Science.}
Takahiro Kawadu,$^{2}$ Shogo Nishiyama,$^{2}\dagger$ \newauthor
Takahiro Nagayama,$^{2,3}$ Hirofumi Hatano,$^{3}\dagger$
Motohide Tamura,$^{4}$ Ian S. Glass$^{5}$ \newauthor
and Tetsuya Nagata$^{2}$ \\
$^{1}$ Institute of Astronomy, the University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo
181-0015, Japan \\
$^{2}$ Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho,
Sakyo-ku, Kyoto 606-8502, Japan \\
$^{3}$ Department of Astrophysics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya
464-8602, Japan \\
$^{4}$ National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo
181-8588, Japan \\
$^{5}$ South African Astronomical Observatory, PO Box 9, 7935, Observatory, South
Africa \\
}

\begin{document}

\date{Accepted 2009 July 15. Received 2009 June23; in original form 2009 May 14}
\volume{399}
\pagerange{1709--1729} \pubyear{2009}

\maketitle

\begin{abstract}
We report the results of a near-infrared survey for long-period variables
in a field of view of $20 \times 30$~arcmin$^2$ towards
the Galactic Centre (GC).
We have detected 1364 variables, of which 348 are identified with those
reported in Glass et al. We present a catalogue and photometric measurements
for the detected variables and discuss their nature. We also establish
a method for the simultaneous estimation of distances and extinctions
using the period-luminosity relations for the JHKs bands. Our method is
applicable to Miras with periods in the range 100--350~d and mean magnitudes
available in two or more filter bands. While $J$ band means are often
unavailable for our objects because of the large extinction, we estimated
distances and extinctions for 143 Miras whose $H$- and $K_{\mathrm{s}}$-band
mean magnitudes
are obtained. We find that most are located at the same distance to within
our accuracy. Assuming that the barycentre of these Miras corresponds
to the GC, we estimate its distance modulus to be 14.58 $\pm$0.02~(stat.)
$\pm$0.11~(syst.)~mag, corresponding to 8.24 $\pm$0.08~(stat.)
$\pm$0.42~(syst.)~kpc. We have assumed the distance modulus to
the Large Magellanic
Cloud to be 18.45~mag, and the uncertainty in this quantity is included
in the above systematic error. We also discuss the large and highly
variable extinction. Its value ranges from 1.5~mag to larger than 4~mag
in except towards the thicker dark nebulae and it varies in a complicated
way with the line of sight. We have identified mid-infrared counterparts
in the {\it Spitzer}/IRAC catalogue of Ramirez et al.\  for most of our variable
 and find that they follow rather narrow period-luminosity relations
in the 3.6--8.0~$\mu$m wavelength range.
\end{abstract}

\begin{keywords}
stars: AGB and post-AGB -- stars: variables: other -- dust, extinction -- Galaxy:
centre -- Galaxy: structure -- infrared stars
\end{keywords}

\end{document}