view Abstract Citations (549) References (83) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The formation of emission lines in quasars and Seyfert nuclei Kwan, J. ; Krolik, J. H. Abstract The photoionization and heating throughout a quasar emission-line cloud optically thick at the Lyman edge are calculated. Photoionization and collisional ionization from excited states of hydrogen are included, which maintain a substantial electron fraction after the exhaustion of Lyman continuum photons halts ground-state photoionization. Observed values are explained for Ly-alpha/H-beta, H-alpha/H-beta, P-alpha/H-alpha, He I 5876/H-beta, O I 8446/H-alpha, and Mg II 2798/H-beta. The dependence of line strengths on physical conditions is discussed, and plotting Fe II/4570/H-beta versus Balmer continuum/H-beta is suggested. Other observations are also suggested, and the degree of asymmetry is given between the forward and backward emission of lines from a finite slab to make possible the use of comparative line profile studies to elucidate cloud kinematics. Publication: The Astrophysical Journal Pub Date: November 1981 DOI: 10.1086/159395 Bibcode: 1981ApJ...250..478K Keywords: Astronomical Models; Emission Spectra; Galactic Nuclei; Line Spectra; Quasars; Seyfert Galaxies; Balmer Series; Ionic Collisions; Iron; Lyman Spectra; Metal Ions; Optical Thickness; Photoionization; Plasma Heating; Spectral Energy Distribution; Astrophysics full text sources ADS |