Detection of interstellar NH/sub 3/ in the far-infrared: warm and dense gas in orion-KL

Journal Article · Wed Jun 01 00:00:00 EDT 1983 · Astrophys. J., Lett. Ed.; (United States)

DOI:https://doi.org/10.1086/184045· OSTI ID:6049322

Townes, C H; Genzel, R; Watson, D M; Storey, J W.V.

We report the detection of the (J,K) = a(4,3)..-->..s(3,3) rotation-inversion transition of ammonia at 124.6 ..mu..m toward the center of the Orion-KL region. The line is in emission and has a FWHM> or =30 km s/sup -1/. The far-IR ammonia line emission probably comes mainly from the ''hot core,'' a compace region of warm, very dense gas previously identified by the radio inversion lines of NH/sub 3/. The a(4,3)..-->..s(3,3) line is very optically thick (tauapprox.10/sup 3/), and since it is seen in emission, radiative excitation of the (4,3) NH/sub 3/ level by far-IR emission from dust within the source can be ruled out. Radiative excitation via the 10 ..mu..m rovibrational transitions of NH/sub 3/ also seems unlikely. Hence, the (4,3) level is probably collisionally excited and the gas in the hot core region is warmer than the dust. Since the far-IR line emission is highly trapped, densities of approx.10/sup 7/ cm/sup -3/ are high enough to explain the observations. Shock heating by the mass outflow from IRc2 may account for the high gas temperatures in the hot core region.

• Research Organization: Department of Physics, University of California, Berkeley
• OSTI ID: 6049322
• Journal Information: Astrophys. J., Lett. Ed.; (United States), Journal Name: Astrophys. J., Lett. Ed.; (United States) Vol. 269:1; ISSN AJLEA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AMMONIA
COSMIC DUST
COSMIC GASES
DUSTS
ELECTROMAGNETIC RADIATION
EMISSION SPECTRA
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITATION
EXCITED STATES
FAR INFRARED RADIATION
FLUIDS
GASES
HYDRIDES
HYDROGEN COMPOUNDS
INFRARED RADIATION
INFRARED SPECTRA
INTERSTELLAR GRAINS
NEBULAE
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
PARTICLES
RADIATIONS
ROTATIONAL STATES
SPECTRA
VIBRATIONAL STATES