HYPERION. Shedding light on the first luminous quasars: A correlation between UV disc winds and X-ray continuum

TL;DR

This study reveals a significant correlation between UV disc wind velocities and X-ray spectral slopes in luminous quasars at redshift >6, indicating a link between disc winds, corona configuration, and black hole growth.

Contribution

It uncovers a novel correlation between UV disc wind velocities and X-ray spectral properties in high-redshift quasars, suggesting a connection between disc winds and SMBH growth mechanisms.

Findings

Strong correlation between X-ray photon index and disc wind velocity.

Evidence linking SMBH growth rate to X-ray and UV wind properties.

Implication that SMBHs grow mainly via fast accretion at high redshift.

Abstract

One of the main open questions in the field of luminous ($L_{\rm bol}>10^{47}\,\rm erg\,s^{-1}$) quasars (QSOs) at $z \gtrsim 6$ is the rapid formation ($< 1\,$Gyr) of their supermassive black holes (SMBHs). For this work we analysed the relation between the X-ray properties and other properties describing the physics and growth of both the accretion disc and the SMBH in QSOs at the Epoch of Reionization (EoR). The sample consists of 21 $z>6$ QSOs, which includes 16 sources from the rapidly grown QSOs from the HYPERION sample and five other luminous QSOs with available high-quality archival X-ray data. We discovered a strong and statistically significant ($>3\sigma$) relation between the X-ray continuum photon index ($\Gamma$) and the $\rm C\,IV$ disc wind velocity ($v_{\rm C\,IV}$) in $z>6$ luminous QSOs, whereby the higher the $v_{\rm C\,IV}$, the steeper the $\Gamma$. This relation suggests a link between the disc-corona configuration and the kinematics of disc winds. Furthermore, we find evidence at $>2-3\sigma$ level that $\Gamma$ and $v_{\rm C\,IV}$ are correlated to the growth rate history of the SMBH. Although additional data are needed to confirm it, this result may suggest that, in luminous $z>6$ QSOs, the SMBH predominantly grows via fast accretion rather than via initial high seed BH mass.