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Is the Broad-Line Region Expanding?1

Published online by Cambridge University Press:  12 April 2016

Kan Liang
Affiliation:
Department of Astronomy, Beijing Normal University, Beijing100875, China
Xiang-Tao He
Affiliation:
Department of Astronomy, Beijing Normal University, Beijing100875, China
Zhong-min Wang
Affiliation:
Institute for Space Astrophysics, Department of Applied Physics, Shanghai Jiao Tong University, Shanghai 200030, China
Jun-Han You
Affiliation:
Institute for Space Astrophysics, Department of Applied Physics, Shanghai Jiao Tong University, Shanghai 200030, China

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We suggest that the broad-line regions (BLRs) of QSOs with broad emissionlines (BALs) are expanding, i.e., the clouds are undergoing radial outflow, as illustrated simply in Fig. 1. At least the following observational facts can be explained:

  1. 1. Optical observations show that some moderate and high-redshift QSOs have BALs. The number of these QSOs is about 3–10% of all QSOs (Foltz et al. 1990). One can see in Fig. 2 that very low-redshift QSOs have no BALs.

  2. 2. Almost all BAL QSOs exhibit zabs < zem.

  3. 3. High-resolution observations reveal that the widths of the broad absorption lines are narrower than that of the corresponding emission line for all BAL QSOs, i.e. Δλ ab < Δλ em.

Type
IV. Physics of the Broad-Line Region
Copyright
Copyright © Astronomical Society of the Pacific 1997

Footnotes

1

This work is supported by the National Natural Science Foundation of China.

References

Foltz, C.B., et al. 1990, BAAS, 22, 806.Google Scholar
Hazard, C., et al. 1984, ApJ, 282, 33.Google Scholar
Hewitt, A., & Burbidge, G. 1993 ApJS, 87.Google Scholar
Sargent, W.L.W., et al. 1989 ApJS, 69, 703.Google Scholar
Turnshek, D.A. 1986, in QSO Absorption Lines, ed. Blades, J.C., Turnshek, D., and Norman, C.A., (Cambridge: Cambridge Univ. Press), p. 17.Google Scholar