A Complete Survey of the Central Molecular Zone in NH3

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 -1.000 < l < 1.625 deg, -0.375 < b < +0.250 deg. 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 Sawada et al. (2001) 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''.

21 pages, 14 figures, accepted for PASJ

References in corpus (1)

• New 60-cm Radio Survey Telescope with the Sideband-Separating SIS Receiver for the 200 GHz Band

Cited by in corpus (13)

• The Bolocam Galactic Plane Survey IV: 1.1 and 0.35 mm Dust Continuum Emission in the Galactic Center Region
• The Central 300 pc of the Galaxy probed by infrared spectra of H${}_3^{+}$ and CO: part I. Predominance of warm and diffuse gas and high H${}_2$ ionization rate
• Nuclear Spirals in the inner Milky Way
• Probing high-redshift quasars with ALMA. I. Expected observables and potential number of sources
• Mass Supply to Galactic Center due to Nested Bars in the Galaxy
• HCN $J$=4-3, HNC $J$=1-0, ${\mathrm{H}}^{13}\mathrm{CN}$ $J$=1-0, and $\mathrm{H}{\mathrm{C}}_3\mathrm{N}$ $J$=10-9 Maps of Galactic Center Region I: Spatially-Resolved Measurements of Physical Conditions and Chemical Composition
• Stochastic Noncircular Motion and Outflows Driven by Magnetic Activity in the Galactic Bulge Region
• Kinetic temperatures toward X1/X2 orbit interceptions regions and Giant Molecular Loops in the Galactic center region
• NH3 in the Galactic Center is formed in Cool Conditions
• Warm ISM in the Sgr A Complex. I: Mid-J CO, atomic carbon, ionized atomic carbon,and ionized nitrogen sub-mm/FIR line observations with the Herschel-HIFI and NANTEN2/SMART telescopes
• Ammonia mapping observations toward the Galactic massive star-forming region Sh 2-255 and Sh 2-257
• A Multi-Line Ammonia Survey of the Galactic Center Region with the Tsukuba 32-m Telescope - I. Observations and Data
• Ammonia mapping observations of the Galactic infrared bubble N49: Three NH${}_3$ clumps along the molecular filament