Kinetic temperatures in Galactic Center molecular clouds

Details Kinetic temperatures in Galactic Center molecular clouds Kinetic temperatures in Galactic Center molecular clouds

Dec 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993a%26a...280..255h&link_type=abstract

Astronomy and Astrophysics (ISSN 0004-6361), vol. 280, no. 1, p. 255-267

Astronomy and Astrophysics

Astronomy

80

Ammonia, Electron Transitions, Emission Spectra, Galactic Bulge, Gas Temperature, Interstellar Matter, Inversions, Line Spectra, Metastable State, Molecular Clouds, Radio Astronomy, Centimeter Waves, Interstellar Magnetic Fields, Rotational States, Superhigh Frequencies

Scientific paper

Measurements of six metastable (J = K) inversion transitions of ammonia for 36 clouds in the galactic center region are presented. Most of the clouds are not related to Sgr A or Sgr B2. In order to minimize the effect of weather, either the (J,K) = (1,1), (2,2) and (4,4) or the (4,4) and (5,5) inversion lines of para-NH3 were measured simultaneously. A common calibration was obtained by forcing the integrated intensities of the (4,4) inversion line spectra from different periods to agree. The (3,3) and (6,6) lines of orthor-NH3 were also measured simultaneously. A determination of the rotational temperatures, Trot, obtained from these lines shows that there must be at least two kinetic temperature regimes in these clouds. In a few cases, small maps of the clouds were made; two of these show that the distribution of the (1,1) and (2,2) inversion lines are similar, but differ markedly from that of the (4,4) inversion line. An analysis of the data shows that the warmer temperature is approximately 200 K, the cooler is approximately 25 K. The warmer gas contains about approximately 25% of the total column density of NH3. The heating processes which give rise to the high kinetic temperatures in these clouds are not certain: These may include and enhanced flux of low energy cosmic rays, cloud-cloud collisions, or ion-slip (ambipolar diffusion).

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