Vent ultra-rapide dans le quasar J2318 : un écoulement relativiste à 0,3c ✛ ✦

Résumé original

tel que rédigé par les auteurs, en anglais arXiv:2606.06226v1

We report the fastest quasar outflow first detected in the ultraviolet, via variable C IV and Si IV absorption at outflow velocities $$-77,000$$ km s$$^{-1}$$ to at least $$-90,000$$ km s$$^{-1}$$, in the radio-quiet quasar SDSS J231854.31+243954.2 (J2318). J2318 is a weak-lined quasar in the rest-frame ultraviolet, but Gemini GNIRS spectroscopy reveals an H$$\alpha$$ redshift of $$z=2.6781\pm0.0004$$. A twenty-year photometric time series shows peak-to-peak variability of 0.5 mag in the $$g$$ band. The C IV outflow strengthened monotonically over three epochs spanning $$\sim$$2.2 rest-frame years. The existence of such a high-velocity outflow implies that models of quasar outflows must be able to either accelerate gas to $$0.3c$$ while still preserving C IV and Si IV ions, or enable the formation of C IV and Si IV ions in gas which has been accelerated to $$0.3c$$. Virial estimates reveal a black-hole mass of $$1.65\times10^9~M_\odot$$, which leads to an Eddington luminosity and Eddington ratio of $$2.4\times10^{47}$$ erg s$$^{-1}$$ and $$0.45$$, respectively. Using very conservative assumptions, the UV-absorbing outflow alone has an estimated mass loss of $$>0.82~M_\odot~{\rm yr}^{-1}$$ and a kinetic luminosity ratio $$L_{kin}/L_{bol}\geq0.75$$%. The lower limit is just above the threshold usually cited for significant feedback on the host galaxy. Comparison to PDS 456, the only other known quasar with a UV-absorbing outflow at $$0.3c$$, suggests that the true $$\dot{M}$$ and $$L_{kin}/L_{bol}$$ could be up to two orders of magnitude larger.