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The emission of hydrogen radio recombination lines from a cloud of cool interstellar matter toward the radio source Cassiopeia
A has been detected. The formation of the radio recombination lines is initiated by cosmic rays. The rate of ionization of
the interstellar hydrogen by cosmic-ray protons measured from the radio recombination lines using the most direct method is
ζH = (1 ± 0.25)×10−16 s−1. This value of ζH is compared with measurements obtained using other methods. 相似文献
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We carried out millimeter-range observations of carbon radiolines from Photo-Dissociation Regions (PDRs). Comparison with
observations of these objects in infrared fine structure lines of CII and OI allows one to determine the physical conditions
in the PDRs (density, temperature, and thickness of the PDR layer) that were done for several regions connected to HII regions.
It is shown that recombination radiolines also allow the kinematics of the complexes including HII regions and PDRs to be
traced. 相似文献
3.
R.L. Sorochenko 《Astronomische Nachrichten》1989,310(5):389-398
Radio recombination lines (RRL) discovered about 25 years ago became a very effective tool for the investigation of interstellar matter (ISM). These lines are unique by the number of transitions and the spectral range observed: from 2 mm to 20 m wavelength. This allows to study the ISM under variety of physical conditions which differ by 7 to 8 orders of magnitude in density and 3 orders of magnitude in temperature. RRL allow to determine the main physical conditions in HII and HI-CII regions, to map the galactic distribution of ionized hydrogen, and to obtain the helium abundance of the ISM. Furthermore, the information contained in the RRL allows to estimate the intensity of cosmic rays and to draw conclusions on the galactic evolution. The physical properties of the RRL and the results obtained by observations of RRLs are reviewed. 相似文献
4.
Observations of the C56α line—the first carbon radio recombination line in the millimeter waveband—in the directions of the Orion Bar, NGC 2024, and W3 are reported. The results are analyzed together with data for the IR fine-structure lines of CII and OI, enabling unambiguous determination of the temperature and density in the photodissociation regions separating the HII regions and parent molecular clouds. 相似文献
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