Abstract

Two sets of relationships relate QSO UV to soft X-ray continua with the broad-line region. These are (i) the Baldwin relationships, which are inverse relationships between the broad-line equivalent width and the continuum luminosity, and (ii) Boroson & Green's optical "Principal Component 1'' relationships, linking steeper soft X-ray spectra with narrower Hβ emission, stronger Hβ blue wings, stronger optical Fe II emission, and weaker [O III] λ5007 lines. In order to understand these relationships, we extended the spectra into the UV for 22 QSOs with high-quality soft X-ray spectra. These are from the complete sample of QSOs from the Bright Quasar Survey for which Laor et al. demonstrated strong luminosity and X-ray-optical Principal Component 1 relationships. We show that these extend to a whole new set of UV relationships: Principal Component 1 (in the sense of steeper X-ray spectra) is related to narrower C III] λ1909 lines, larger Si III] λ1892/C III] λ1909 ratios (a high-density indicator), stronger low-ionization lines, and weaker C IV λ1549 but stronger N V λ1240 lines. We speculate that high accretion rates are linked to high columns of dense (~1011 cm-3), nitrogen-enhanced, low-ionization gas from nuclear starbursts. Line width, inverse Fe II-[O III] and inverse Fe II-C IV relationships hint at the geometrical arrangement of this gas. These Principal Component 1 relationships appear to be independent of luminosity and therefore of the Baldwin relationships.

Document Type

Article

Publication Date

4-20-1999

Notes/Citation Information

Published in The Astrophysical Journal Letters, v. 515, no. 2, p. L53-L56.

© 1999. The American Astronomical Society. All rights reserved. Printed in the U.S.A.

The copyright holder has granted permission for posting the article here.

Digital Object Identifier (DOI)

https://doi.org/10.1086/311980

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