First detection of ultrafast outflows in a quiescent galaxy

Outflows in active galactic nuclei (AGNs) are recognized as fundamental mechanisms driving the coevolution of supermassive black holes (SMBHs) and their host galaxies by regulating the gas reservoir for SMBH growth and host star formation. Although powerful outflows are frequently detected in gas-rich, active star-forming galaxies, their existence and potential impact within gas-poor, quiescent galaxies remain poorly understood. We report the first detection of a powerful ultrafast outflow (UFO) in a nearby quiescent galaxy KUG 1208+386, providing a multi-scale analysis of AGN winds from nuclear to galactic scales. We performed Bayesian-based X-ray spectroscopy of archival and observations to characterize the circumnuclear materials and UFOs. Using optical spectra from the Dark Energy Spectroscopic Instrument ( ), we constrained the kinematics of the galactic-scale outflows and star formation history of the host galaxy. Additionally, we derived galaxy properties, such as stellar mass (M_⋆) and star formation rate (SFR), via multiwavelength spectral energy distribution fitting of photometric data. XMM-Newton NuSTAR DESI We detect a nuclear X-ray UFO with a velocity of v_ ̊m out ≈ -0.07c and a kinetic power of dot E _ ̊m UFO =(0.8 6.5) ,erg/s. This power is sufficient to drive effective AGN feedback (dot _ -- 10^ 43 E ̊m UFO /L_ =(1 8)%) and far exceeds the galactic Edd -- OIII outflow power ∼ 10^ 40 ,erg/s. Host galaxy analysis reveals a massive quiescent system (specific SFR sim3 , ^ -12 yr -1 ) quenched ∼9,Gyr ago. The central AGN is obscured by a line-of-sight column density of $łog (N_ ^ / ^ H LOS cm -2 ) and the circumnuclear scattering material is Compton-thick łog( N_ ^ / ^ H scatter cm -2 )=24.7^ +0.8 _ -0.5 , indicating a dense nuclear environment. The discovery of a nuclear UFO in a long-quenched massive galaxy challenges the paradigm that UFOs are exclusive to gas-rich, star-forming systems, suggesting that they are governed by the local circumnuclear environments rather than the global gas reservoir. Our results indicate that episodic, powerful winds can maintain the quiescent state of KUG 1208+386 over gigayear timescales, supporting a wind-driven "maintenance" mode of AGN feedback that is distinct from the classical jet mode. Future deep X-ray and submillimeter observations are essential for definitively characterizing the cold gas reservoir and the coupling efficiency among multiphase and multi-scale outflows.