The WISSH quasars project VII. The impact of extreme radiative field in the accretion disk and X-ray corona interplay

Abstract

Hyperluminous quasars ($L_{\mathrm{bol}}\gtrsim 10^{47}$ erg s${}^{-1}$) are ideal laboratories to study the interaction and impact of extreme radiative field and the most powerful winds in the AGN nuclear regions. They typically exhibit low coronal X-ray luminosity ($L_{\mathrm{X}}$) compared to the UV and MIR radiative outputs ($L_{\mathrm{UV}}$ and $L_{\mathrm{MIR}}$) with a non-negligible fraction of them reporting even $\sim$1 dex weaker $L_{\mathrm{X}}$ compared to the prediction of the well established $L_{\mathrm{X}}$-$L_{\mathrm{UV}}$ and $L_{\mathrm{X}}$-$L_{\mathrm{MIR}}$ relations followed by the bulk of the AGN population. We report in our WISE/SDSS-selected Hyperluminous (WISSH) $z=2-4$ broad-line quasar sample, the discovery of a dependence between the intrinsic 2-10 keV luminosity ($L_{2-10}$) and the blueshifted velocity of the CIV emission line ($v_{\mathrm{CIV}}$) indicative of accretion disc winds. In particular, sources with fastest winds ($v_{\mathrm{CIV}}\gtrsim 3000\mathrm{km}{\mathrm{s}}^{-1}$) possess $\sim$0.5-1 dex lower $L_{2-10}$ than sources with negligible $v_{\mathrm{CIV}}$. No similar dependence is found on $L_{\mathrm{UV}}$, $L_{\mathrm{MIR}}$, $L_{\mathrm{bol}}$, photon index and absorption column density. We interpret these findings in the context of accretion disc wind models. Both magnetohydrodynamic and line-driven models can qualitatively explain the reported relations as a consequence of X-ray shielding from the inner wind regions. In case of line-driven winds, the launch of fast winds is favoured by a reduced X-ray emission, and we speculate that these winds may play a role in directly limiting the coronal hard X-ray production.

10 pages (including Appendix), 4 figures. Astronomy & Astrophysics Letters in press. Title numbering changed to match the published version