Hidden Monsters with SPHEREx. I.

We confirm 76 new HRQs with redshifts of 1.5<z_sys_<3.9, dust-corrected optical continuum luminosities of log_10_({lambda}L_{lambda}(3000{AA}_[erg/s])>47.0, and line-of-sight extinctions of 0.4<E(B-V)<1.6 (A_V_~1-5mag). This more than doubles the number of confirmed HRQs at z_sys_>1.5 including the first 7 HRQs ever identified at z>3. A UV excess consistent with scattered quasar emission is detected in 76 per cent of SPX HRQs.

We conclusively demonstrate that HRQs are hot-dust poor compared to blue quasars of similar luminosities and redshifts. We find that the 6um continuum luminosities of HRQs are systematically lower at fixed 3000{AA}, continuum luminosity relative to blue Quaia quasars, suggesting that HRQs are deficient in both hot and warm dust components. This combination of depleted torus-scale dust reservoirs and higher luminosities compared to hot DOGs and blue quasars supports a scenario in which HRQs represent a blow-out phase, when strong feedback has begun to clear the central regions of obscuring material.