A relativistic inflow candidate in a quasar at cosmic noon

Abstract

Cosmic noon ($z\sim2$) marks the peak epoch of cosmic star formation and black hole accretion activity, where strong accretion and outflows are expected. We report two candidate absorption features in the \textit{XMM-Newton} spectrum of the quasar WISEA~J094835.95+432302.6 at $z=1.893$. Two redshifted features occur at rest-frame energies of $\sim4.65$ and $\sim5.75$keV with confidence levels of 99.3% and 94.1%, respectively, estimated from Monte Carlo (MC) simulations considering the look-elsewhere effect. These features can be explained by the Fe XXV/XXVI K-shell transitions from one ultra-fast inflow (UFI) with an apparent velocity of $0.37^{+0.02}_{-0.01}c$. If confirmed by follow-up \textit{XMM-Newton} observations, these detections would extend reported UFI candidates from the local Universe to cosmic noon, offering a rare laboratory for black hole accretion at the peak of their growth.