New Molecular Absorption Line System: The Gravitational Lens PKS 1830-211 at Z = 0.88582
Abstract
The detectability of molecular absorption lines is largely independent of the excitation of the gas and can give accurate column densities, abundance ratios and excitation temperature for a wide range of different gas conditions. Moreover, when seen towards distant radio-loud quasars, the small angular extent of the background source makes the observational sensitivity of absorption lines independent of distance. Another advantage with molecular lines is that the energy of the first rotational level of several abundant molecules corresponds to temperatures in the range 4-5 K, while the second level corresponds to 12-15 K. In diffuse molecular clouds the radiation field is likely to be dominated by the cosmic microwave background (CMB) radiation, while collisional excitation can be low. Big Bang Cosmology predicts that the temperature of the CMB radiation increases linearly with redshift. Molecular absorption lines therefore has the potential to give upper limits to the CMB temperature at high redshifts.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- November 1995
- Bibcode:
- 1995STIN...9818647W
- Keywords:
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- Molecular Absorption;
- Gravitational Lenses;
- Big Bang Cosmology;
- Absorption Spectra;
- Line Spectra;
- Excitation;
- Diffuse Radiation;
- Gravitational Fields;
- Molecular Clouds;
- Red Shift;
- Quasars;
- Hydrogen;
- Radiation Distribution;
- Background Radiation;
- Astrophysics