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Absorption Against the Cosmic 2.7 K Background

Published online by Cambridge University Press:  26 May 2016

Suresh Chandra  and
W.H. Kegel
Suresh Chandra
Affiliation:
School of Physical Sciences, SRTM University, Nanded 431 606, India
W.H. Kegel
Affiliation:
Institut für Theoretische Physik, J.W. Goethe-Universität, D-60054 Frankfurt am Main, Germany

Extract

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Observation of an interstellar line in absorption against the cosmic 2.7 K background is an unusual phenomenon. The intensity, Iv, of a line generated in an interstellar cloud, with homogeneous excitation conditions, is given by where Iv,bg is the intensity of the continuum against which the line is observed, τv the optical depth of the line, and Sv the source function, which is the Planck's function at the excitation temperature Tex, i.e., Sv = Bv(Tex). Observation of an interstellar line in absorption against the cosmic 2.7 K background, obviously, implies 0 K < Tex < 2.7 K, which requires rather peculiar physical conditions in the molecule, generating the line.

Type
Part 1: Radio Source Surveys and Cosmology
Information
Symposium - International Astronomical Union , Volume 199: The Universe at Low Radio Frequencies , 2002 , pp. 66 - 67
Copyright
Copyright © Astronomical Society of the Pacific 2002 

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