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Emission Lines in the Far-UV and Extreme-UV Region

Published online by Cambridge University Press:  12 April 2016

W. Zheng
W. Zheng*
Affiliation:
Center for Astrophysical Sciences, Johns Hopkins University, Baltimore, MD 21218, USA

Abstract

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Recent observations with HST and HUT have been made of the spectral region shortward of Lyα in AGN. Emission lines in this region, such as O VIλ1035 and Ne VIIIλ774, are mainly produced by collisional excitation. Their strengths and the lack of other significant emission lines of higher excitation energy indicate a temperature of ~ 6 × 104 K for the highly ionized gas in line-emitting clouds. Model calculations suggest that the strength of O VI and Ne vIII emission is correlated to the intensity of the high-energy photons above 100 eV. Therefore, these lines are useful diagnostics of the continuum shape in the soft X-ray range. The luminosity dependence of emission-line equivalent widths is more prominent for lines of higher ionization level, suggesting that the UV bump in AGN spectra may be weaker at higher luminosities.

Type
II. Broad Emission Lines
Information
International Astronomical Union Colloquium , Volume 159: Emission Lines in Active Galaxies: New Methods and Techniques , 1997 , pp. 108 - 115
Copyright
Copyright © Astronomical Society of the Pacific 1997

References

Baldwin, J.A. 1977, ApJ, 214, 679.Google Scholar
Davidsen, A.F. 1993, Science, 259, 327.Google Scholar
Davidsen, A.F., Kriss, G.A., & Zheng, W. 1996, Nature, 380, 47.Google Scholar
Eastman, R.G., & MacAlpine, G.M. 1985, ApJ, 299, 785.Google Scholar
Ferland, G.J. 1993, Univ. Kentucky Dept. of Phys. & Astron. Internal Report.Google Scholar
Hamann, F., Zuo, L., & Tytler, D. 1995, ApJ, 444, L69.CrossRefGoogle Scholar
Kinney, A.L., Huggins, P.J., Bregman, J.N., & Glassgold, A.E. 1985, ApJ, 291, 128.Google Scholar
Kinney, A.L., Rivolo, A.R., & Koratkar, A.P. 1990, ApJ, 357, 338,Google Scholar
Kriss, G.A., Davidsen, A.F., Blair, W.P., Ferguson, H.C., & Long, K.S. 1992, ApJ, 394, L37.Google Scholar
Krolik, J.H., & Kallman, T.R. 1988, ApJ, 324, 714.Google Scholar
Kruk, J.W., Durrance, S.D., Kriss, G.A., Davidsen, A.F., Blair, W.P., Espey, B.R., & Finley, D.S. 1995, ApJ, 454, L1.Google Scholar
Kwan, J., & Krolik, J.H. 1981, ApJ, 250, 478.Google Scholar
Lanzetta, K.M., Turnshek, D.A., & Sandoval, J. 1992, ApJS, 84, 109.Google Scholar
Laor, A., Bancali, J.N., Januzzi, B.T., Schneider, D.P., Green, R.F., & Hartig, G.F. 1994, ApJ, 420, 110.Google Scholar
Netzer, H., Elitzur, M., & Ferland, G.J. 1985, ApJ, 299, 752.CrossRefGoogle Scholar
Osterbrock, D.E. 1989, Astrophysics of Gaseous Nebulae and Active Galactic Nuclei (Mill Valley: University Science Books).Google Scholar
Peterson, B.M. 1993, PASP, 105, 247.Google Scholar
Vogel, S., & Reimers, D. 1995, A&A, 294, 377.Google Scholar
Walter, R., & Fink, H.H. 1993, A&A, 274, 105.Google Scholar
Zheng, W., Fang, L.Z., & Binette, L. 1992, ApJ, 392, 74.CrossRefGoogle Scholar
Zheng, W., Kriss, G.A., & Davidsen, A.F. 1995, ApJ, 440, 606.CrossRefGoogle Scholar
Zheng, W., Kriss, G.A., Telfer, R.C., Grimes, J.P., & Davidsen, A.F. 1996, ApJ, submitted.Google Scholar