Permitted fe II Emission in Seyfert 1 Galaxies and QSOs I. Observations

Spectrophotometric observations of 19 Seyfert 1 galaxies and four quasi-stellar objects with strong Fe ii emission are presented. Relative emission-line intensities, equivalent widths, and continuum slopes were measured for each object. The optical spectra of the Fe II Seyfert 1 galaxies and QSOs are difficult to distingnish from ordinary Seyfert 1 galaxies, except in the strength of the Fe u emission. Analysis of the continuum and emission-line data (excluding Fe u) indicates that densities Ne = 10Th 1010 cm -3 and temperatures T = 50()( 20,000 K likely characterize the broad4ine regions. Collisional and (or) radiative-transfer effects may contribute to the observed steep decrements and large Hfl equivalent widths. Tile narrow-line gas has regions of high ionization and high density (Ne = cm - 3) which produce lines such as [0 m] AA4959, 5007 and [Fe vii] A6087, and lower density zones (Ne = I0 cm -3) where the low-ionization lines such as [0 1] A6300 and [S ii] AA6716, 6731 are emitted. Large variations in the spectral features of the Seyfert 1 galaxy Mrk 541 were observed over a 2 year period. The Fe ii emission apparently originates in the same high-density regions which produce the broad H I Balmer lines. Tile relative intensities of the Fe ii lines are very similar from object to object, indicating that the same physical conditions and excitation mechanism are responsible for the emission. Tile Fe ii lines appear to have approximately the same widths and proffles as the broad Balmer lines. Tile weakness of the [Fe ii] lines allows a lower limit for the electron density Ne 10 to be set. A survey of 20 QSOs with redshifts 0.35 < z < 0.70 yielded only two objects with moderately strong Fe ii emission, suggesting that Fe ii emission is uncommon among QSOs in this redshift range. Tile QSOs also appear to have weaker He ii A4686 emission than the Fe ii Seyfert 1 galaxies. All of the QSOs studied (including those with Fe ii) show flatter continuous spectra in the wavelength range AA30007000 than the Fe II Seyfert 1 galaxies. Subject headings: galaxies: Seyfert - quasars - spectrophotometry