2007/07/06 by Takumi Nagayama, Toshihiro Omodaka, Toshihiro Handa +4 · 19 citations
Earth and Planetary Sciences · Physics and Astronomy · #Ambipolar diffusion #Astrophysics #Astrophysics and Star Formation Studies #Atmospheric Ozone and Climate #Atomic and Molecular Physics #Envelope (radar) #Flux (metallurgy) #Galactic plane #Galaxy #Kinetic energy #Luminosity #Materials science #Mean kinetic temperature #Molecular cloud #Physics #Plasma #Stars #astro-ph
paper · pdf · doi:10.1093/pasj/59.5.869
published in Publications of the Astronomical Society of Japan 59(5), 869-887 (Oxford University Press) · 21 pages, 14 figures, accepted for PASJ
arxiv created 2007/07/06 · openalex publication_date 2007/10/25 · arxiv updated 2015/05/12 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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 -1\rlap.∘000 ≤ l ≤ 1\rlap.∘625 and -0\rlap.∘375 ≤ b ≤ 0\rlap.∘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 temperatures 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 of our observations with a CO survey by Sawada et al. (2001, ApJS, 136, 189) shows that the NH3 emitting region is surrounded by a high-pressure region on the longitude–velocity (l - v) plane. Although NH3 emission traces dense gas, it does not extend over 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 that 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”.