A Complete Survey of the Central Molecular Zone in NH3

Takumi Nagayama(1), Toshihiro Omodaka(2), Toshihiro Handa(3), Hayati Bebe Hajra Iahak(1), Tsuyoshi Sawada(4), Takeshi Miyaji(5), and Yasuhiro Koyama(6)


(1) Graduate School of Science and Engineering, Kagoshima University,, 1-21-30 K\hatorimoto, Kagoshima 890-0065
(2) Faculty of Science, Kagoshima University, 1-21-30 K\hatorimoto, Kagoshima 890-0065
(3) Institute of Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015
(4) Nobeyama Radio Observatory, National Astronomical Observatory of Japan,, Minamimaki, Minamisaku, Nagano 384-1305
(5) Mizusawa VERA Observatory, National Astronomical Observatory of Japan,, 2-21-1 Osawa, Mitaka, Tokyo 181-8588
(6) Kashima Space Research Center, National Institute of Information and Communications Technology,, 893-1 Hirai, Kashima, Ibaraki 314-8510

Paper: PASJ, OCT 2007, Vol.59, No.5

Weblink: http://jp.arxiv.org/abs/0707.0911

EPrint Server: 0707.0911

Abstract:

We present a map of the major part of the central molecular zone (CMZ) of simultaneous observations in the NH3 (J,K) = (1,1) and (2,2) lines using the Kagoshima 6-m telescope. The mapped area is \timeform-1D.000 <= l <= \timeform1D.625, \timeform-0D.375 <= b <= \timeform+0D.250. The kinetic temperatures derived from the (2,2) to (1,1) intensity ratios are 20-80 K or exceed 80 K. The gases corresponding to temperature of 20-80 K and >= 80 K contain 75% and 25% of the total NH3 flux, respectively. These temperatures indicate that the dense molecular gas in the CMZ is dominated by gas that is warmer than the majority of the dust present there. A comparison with the CO survey by \citetsawada shows that the NH3 emitting region is surrounded by a high pressure region on the l-v plane. Although NH3 emission traces dense gas, it is not extended into a high pressure region. Therefore, the high pressure region is less dense and has to be hotter. This indicates that the molecular cloud complex in the Galactic center region has a ``core'' of dense and warm clouds which are traced by the NH3 emission, and an ``envelope'' of less dense and hotter gas clouds. Besides heating by ambipolar diffusion, the hot plasma gas emitting the X-ray emission may heat the hot ``envelope''.

Preprints available from the authors at nagayama@astro.sci.kagoshima-u.ac.jp , or the raw TeX (no figures) if you click here.

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