Evidence for Intrinsic X-ray Weakness Among Red Quasars at Cosmic Noon

Quasar feedback is a key ingredient in shaping galaxy evolution. A rare population of extremely red quasars (ERQs) at z=2-3 are often associated with high-velocity [OIII]λ5008 outflows and may represent sites of strong feedback. In this paper, we present an X-ray study of 50 ERQs to investigate the link between the X-ray and outflow properties of these intriguing objects. Using hardness ratio analysis, we confirm that the ERQs are heavily obscured systems with gas column density reaching N_H=10^23-24 cm^-2. We identify 17 X-ray-non-detected ERQs at high mid-infrared luminosities of ν L_ν,6μ m≳3×10^46 erg s^-1. By stacking the X-ray observations, we find that the non-detected ERQs are on average underluminous in X-rays by a factor of ∼5 for their bolometric luminosities. We consider such X-ray weakness to be due to both gas absorption and intrinsic factors. Moreover, we find that the X-ray-weak sources also display higher-velocity outflows. One option to explain this trend is that weaker X-rays facilitate more vigorous line-driven winds, which then accelerate the [OIII]-emitting gas to kpc-scales. Alternatively, super-Eddington accretion could also lead to intrinsic X-ray weakness and more powerful continuum-driven outflow.