The Correlation between X-ray and UV Properties of BAL QSOs

TL;DR

This study investigates the relationship between X-ray and UV properties of BAL quasars, revealing significant correlations between X-ray weakness and outflow velocities, suggesting X-ray absorption's role in BAL outflow production.

Contribution

It provides a large, diverse sample analysis showing correlations between X-ray weakness and BAL outflow parameters, expanding understanding of BAL quasar properties.

Findings

Significant correlation between X-ray weakness and BALnicity Index.

Significant correlation between X-ray weakness and maximum outflow velocity.

No confirmed correlation between absorption column density and BAL parameters.

Abstract

We compile a large sample of broad absorption lines (BAL) quasars with X-ray observations from the \xmm archive data and Sloan Digital Sky Survey Data Release 5. The sample consists of 41 BAL QSOs. Among 26 BAL quasars detected in X-ray, spectral analysis is possible for twelve objects. X-ray absorption is detected in all of them. Complementary to that of \citet{gall06} (thereafter G06), our sample spans wide ranges of both BALnicity Index (BI) and maximum outflow velocity (\vmax). Combining our sample with G06's, we find very significant correlations between the intrinsic X-ray weakness with both BALnicity Index (BI) and the maximum velocity of absorption trough. We do not confirm the previous claimed correlation between absorption column density and broad absorption line parameters. We tentatively interpret this as that X-ray absorption is necessary to the production of the BAL outflow, but the properties of the outflow are largely determined by intrinsic SED of the quasars.