Issue |
A&A
Volume 367, Number 3, March I 2001
|
|
---|---|---|
Page(s) | 995 - 999 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:20000499 | |
Published online | 15 March 2001 |
Absorption against the cosmic 2.7 K background
1
School of Physical Sciences, S.R.T.M. University, Nanded 431 606, India
2
Institut für Theoretische Physik, J.W. Goethe-Universität, 60054 Frankfurt am Main, Germany
Corresponding author: W. H. Kegel, kegel@astro.uni-frankfurt.de
Received:
25
February
2000
Accepted:
12
December
2000
Two interstellar lines, 1 111 of
formaldehyde at 4.831 GHz,
and 2
211 of cyclopropenylidene at
21.590 GHz, have so far been observed in absorption against the
cosmic 2.7 K background.
Observation of an interstellar line in absorption
against the cosmic 2.7 K background is an unusual phenomenon, and can only be possible
under rather peculiar
conditions developed in the molecule, generating the line. We predict
that two more lines,
3
321 at 27.100 GHz, and 3
322 at
59.550 GHz of cyclopropenylidene, and three lines, 2
211
at 15.600 GHz, 3
321 at 23.100 GHz, and
3
322 at 39.700 GHz of ethylene oxide, may show
absorption against the cosmic 2.7 K background. We speculate that
such peculiar conditions are characteristic for b-type asymmetrical top molecules. -The
observation of these lines may be used to place upper bounds to the density
in the absorbing region.
Key words: molecular processes / ISM: molecules / Cosmology: cosmic microwave background / radio lines: ISM
© ESO, 2001
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