Volume 381, Number 3, JanuaryIII 2002
|Page(s)||L64 - L67|
|Published online||15 January 2002|
Letter to the Editor
The cosmic microwave background radiation temperature at toward QSO 0347–3819*
Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34131 Trieste, Italy
2 Division of Theoretical Astrophysics, National Astronomical Observatory, Mitaka, Tokyo 181-8588, Japan
3 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
4 Observatoire de Genève, 1290 Sauverny, Switzerland
Corresponding author: P. Molaro, firstname.lastname@example.org
Accepted: 28 November 2001
From the analysis of the C+ fine-structure population ratio in the damped Lyα system at zabs = 3.025 toward the quasar Q0347–3819 we derive an upper bound of K on the cosmic microwave background temperature (TCMBR) regardless the presence of other different excitation mechanisms. The analysis of the ground state rotational level populations of H2 detected in the system reveals a Galactic-type UV radiation field ruling out UV pumping as an important excitation mechanism for C+. The low dust content estimated from the Cr/Zn ratio indicates that the IR dust emission can also be neglected. When the collisional excitation is considered, we measure a temperature for the cosmic background radiation of TCMBR = K. The results are in agreement with the TCMBR = K predicted by the hot Big Bang cosmology at zabs = 3.025.
Key words: cosmology: observations: cosmic microwave background / quasars: absorption lines: individual: Q0347–3819
© ESO, 2002
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