Emission Line-Ultraviolet to X-Ray Continuum Correlations: Constraints on the Anisotropy of the Ionizing Continuum in Active Galactic Nuclei

Abstract

Anisotropic emission of the ionizing continuum is a general prediction of the accretion disk models. In this paper, we present the results of correlation analysis of the UV emission line and UV to X-ray continuum properties for a large sample of broad emission line AGNs observed with ROSAT, IUE and HST. We find strong correlations between the CIV/$Ly\alpha$ ratio, the equivalent width of CIV, and the UV to soft X-ray spectral slope. The results are in good agreement with the photoionization calculation, suggesting that the overall ionizing continuum can well match the observed UV to soft X-ray spectrum. These results are consistent with the assumption of isotropic ionizing continuum shape. Our analysis suggests a small range for the ``big blue bump'' cutoff energy for the objects in this sample, consistent with the similar results of Laor et al. (1997) and Walter & Fink (1993) based on the continuum properties . The mean UV-to-X-ray spectral slope is similar to the soft X-ray spectral slope. This similarity also holds for radio-loud and radio-quiet objects separately. This suggests that the two might be drawn from the same distribution. The two spectral slopes are only weakly correlated. The UV to X-ray spectral index is correlated with absolute optical magnitude. This result confirms the earlier suggestion that the ionizing continua are softer for higher luminosity objects.

Accepted for publication in the Astrophysical Journal. 15 pages AAStex + 5 figures + three tables

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• The Soft X-Ray Properties of a Complete Sample of Optically Selected Quasars II. Final Results
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