Ultraviolet and Optical Properties of Narrow‐Line Seyfert 1 Galaxies
Open Access
- 1 May 2003
- journal article
- research article
- Published by IOP Publishing in Publications of the Astronomical Society of the Pacific
- Vol. 115 (807) , 592-608
- https://doi.org/10.1086/374724
Abstract
Narrow‐line Seyfert 1 galaxies (NLS1s) are remarkable for their extreme continuum and emission‐line properties, which are not well understood. New results bearing on the spectroscopic characteristics of these objects are presented here, with the aim of establishing their typical UV and optical spectral behavior. We employ Hubble Space Telescope observations of 22 NLS1s, which represent a substantial improvement over previous work in terms of data quality and sample size. High signal‐to‐noise ratio NLS1 composite spectra are constructed, allowing accurate measurements of the continuum shape and the strengths, ratios, and widths for lines, including weak features that are barely identifiable in other active galactic nuclei composites. We find that the NLS1 sources have redder UV‐blue continua than those typically measured in other quasars and Seyfert galaxies. Objects with UV line absorption show redder spectra, suggesting that dust is important in modifying the continuum shapes. The data also permit a detailed investigation of the previously proposed link between NLS1s and z4 quasars. Direct comparison of their composite spectra, as well as a principal component analysis, suggests that high‐z quasi‐stellar objects do not show a strong preference toward NLS1 behavior.Keywords
All Related Versions
This publication has 55 references indexed in Scilit:
- Reddening, Emission‐Line, and Intrinsic Absorption Properties in the Narrow‐Line Seyfert 1 Galaxy Arakelian 564The Astrophysical Journal, 2002
- Black Hole Mass and Eddington Ratio as Drivers for the Observable Properties of Radio‐loud and Radio‐quiet QSOsThe Astrophysical Journal, 2002
- Emission‐Line Properties ofz > 4 QuasarsThe Astrophysical Journal, 2002
- On the Nature of Intrinsic Absorption in Reddened Seyfert 1 GalaxiesThe Astrophysical Journal, 2001
- Composite Spectra from the FIRST Bright Quasar SurveyThe Astrophysical Journal, 2001
- The Fe II problem in NLS1sNew Astronomy Reviews, 2000
- Intrinsic Absorption Lines in Seyfert 1 Galaxies. I. Ultraviolet Spectra from theHubble Space TelescopeThe Astrophysical Journal, 1999
- The emission-line properties of low-redshift quasi-stellar objectsThe Astrophysical Journal Supplement Series, 1992
- The relationship between infrared, optical, and ultraviolet extinctionThe Astrophysical Journal, 1989
- Luminosity Indicators in the Spectra of Quasi-Stellar ObjectsThe Astrophysical Journal, 1977