Astronomy and Astrophysics – Astronomy
Scientific paper
Mar 1988
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1988sssmp..31..345y&link_type=abstract
Scientia Sinica, Series A - Mathematical, Physical, Astronomical and Technical Sciences (ISSN 0253-5831), vol. 31, March 1988, p
Astronomy and Astrophysics
Astronomy
Cerenkov Radiation, Emission Spectra, Line Spectra, Quasars, Recombination Reactions, Red Shift, Active Galactic Nuclei, Interstellar Gas, Lyman Alpha Radiation, Relativistic Electron Beams
Scientific paper
In the broad-line regions of quasars, there exist three different line-emission mechanisms; i.e., the lines from recombination, the lines from collisional excitation, and the lines from the Cerenkov effect. However, the Cerenkov-line photon can avoid the resonance absorption because of the Cerenkov redshift, and can escape easily from the deep inner part of the gas. The gas then appears more 'transparent' for the Cerenkov line than for the conventional spontaneous transition line. For an optically thick dense gas with sufficient relativistic electrons, the intensity of the Cerenkov line will dominate. Taking the quasar 3 C 273 as an example, it is shown that the calculated Cerenkov Ly-alpha luminosity is in agreement with observations only if N(e) = (1-100) x 10 to the 4th/cu cm.
Cheng Fuhua
You Junhan
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