English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We present Chandra observations of 2106 radio-quiet quasars in the redshiftrange 1.7<z<2.7 from the Sloan Digital Sky Survey (SDSS), through data releasefourteen (DR14), that do not contain broad absorption lines (BAL) in theirrest-frame UV spectra. This sample adds over a decade worth of SDSS and Chandraobservations to our previously published sample of 139 quasars from SDSS DR5which is still used to correlate X-ray and optical/UV emission in typicalquasars. We fit the SDSS spectra for 753 of the quasars in our sample that havehigh-quality (exposure time $\gtrapprox$10 ks and off-axis observation angle<10 arcmin) X-ray observations, and analyze their X-ray-to-optical SEDproperties ($\alpha_{ox}$ and $\Delta\alpha_{ox}$) with respect to the measuredCIV and MgII emission-line rest-frame equivalent width (EW) and the CIVemission-line blueshift. We find significant correlations (at the >99.99%level) between $\alpha_{ox}$ and these emission-line parameters, as well asbetween $\Delta\alpha_{ox}$ and CIV EW. Slight correlations are found between$\Delta\alpha_{ox}$ and CIV blueshift, MgII EW, and the CIV EW to MgII EWratio. The best-fit trend in each parameter space is used to compare the X-rayweakness ($\Delta\alpha_{ox}$) and optical/UV emission properties of typicalquasars and weak-line quasars (WLQs). The WLQs typically exhibit weaker X-rayemission than predicted by the typical quasar relationships. The best-fitrelationships for our typical quasars are consistent with predictions from thedisk-wind quasar model. The behavior of the WLQs compared to our typicalquasars can be explained by an X-ray "shielding" model.

The correlations between optical/UV broad lines and X-ray emission for a large sample of quasars