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 distinguish from ordinary Seyfert 1 galaxies, except in the strength of the Fe II emission. Analysis of the continuum and emission-line data (excluding Fe II) indicates that densities N/sub e/=10/sup 7/-10/sup 10/ cm/sup -3/ and temperatures T=5000--20,000 K likely characterize the broad-line regions. Collisional and (or) radiative-transfer effects may contribute to the observed steep decrements and large H..beta.. equivalent widths. The narrow-line gas has regions of high ionization and high density (N/sub e/=10/sup 4/--10/sup 6/cm/sup -3/) which produce lines such as (O III) lambdalambda4959, 5007 and (Fe VII) lambda6087, and lower density zones (N/sub e/=10/sup 3/cm/sup -3/) where the low-ionization lines such as (O I) lambda6300 and (S II) lambdalambda6716, 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. The 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. The Fe II lines appear to have approximately the same widths and profiles as the broad Balmer lines. The weakness of the (Fe II) lines allows a lower limit for the electron density N/sub e/> or approx. =10/sup 7/cm/sup -3/ to be set.A survey of 20 QSOs with redshifts 0.35< or =z< or =0.70 yielded only two objects with moderately strong Fe II emission, suggesting that Fe II emission is uncommon in this redshift range. The QSOs also appear to have weaker He II lambda4686 emission than the Fe II Seyfert 1 galaxies.
- Research Organization:
- Lick Observatory, Board of Studies in Astronomy and Astrophysics, University of California, Santa Cruz
- OSTI ID:
- 6418382
- Journal Information:
- Astrophys. J., Suppl. Ser.; (United States), Journal Name: Astrophys. J., Suppl. Ser.; (United States) Vol. 38:3; ISSN APJSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Radio
& X-Ray Sources-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATOMIC IONS
BALMER LINES
CHARGED PARTICLES
COSMIC RADIO SOURCES
ELECTRON DENSITY
EMISSION SPECTRA
GALAXIES
IONIZATION
IONS
IRON IONS
MARKARIAN GALAXIES
QUASARS
RED SHIFT
SEYFERT GALAXIES
SPECTRA
SPECTROPHOTOMETRY