Quasar WISSH13: Ultra-Fast Winds from the Cosmic Noon Era ✦
First results from the WISSHFUL program target bright quasars at the Cosmic Noon. Combined XMM-Newton and NuSTAR data for the super-Eddington quasar WISSH13 (z=3.294) delivered the finest broadband X-ray spectrum to date for a non-lensed quasar at such a redshift. Continuum modeling revealed a soft photon index (Γ~2), strong reflection (R~1.4–1.8) with a weak narrow iron line, and a low high-energy cutoff (E_cut~60–80 keV, kTe~15–20 keV). Most notably, two absorption lines at ~7.5 and ~10 keV (rest frame) were detected with 96.7% and 98.9% confidence, interpreted as a blueshifted blend of Fe XXV Heα and Fe XXVI Lyα. They indicate two kinematic components of highly ionized ultra-fast outflow (UFO) at ~0.1c and ~0.3c. The slower wind persisted in archival 2017 data, while the fast one emerged only in 2024, showcasing a layered and variable structure.
Context
During the Cosmic Noon (z~2-4), when the Universe was at peak star formation, supermassive black holes actively devoured matter, powering quasars. Powerful outflows, or 'ultra-fast winds' (UFOs), play a key role in halting this growth by ejecting gas from galaxies. However, their properties at high redshifts remained a mystery due to observational challenges. Quasar WISSH13, located at a distance light traveled for almost 12 billion years (Edwin Hubble first showed that such distant objects recede from us), provides a unique chance to peer into this turbulent process.
Methods
Using the orbiting observatories XMM-Newton and NuSTAR, astronomers conducted simultaneous X-ray observations of WISSH13. Data from 2024 along with archival 2017 data yielded the highest-quality spectrum for an unlensed quasar at z>2. The continuum was modeled with the pexmon and compTT codes, accounting for reflection from a cold disk and Comptonization in the corona. Absorption lines were searched blindly: a narrow Gaussian line was imposed on the baseline model, sweeping the 5-12 keV range in the rest frame. Monte Carlo simulations assessed the significance of detected features to rule out random fluctuations. Xstar photoionization tables, assuming a turbulent velocity of 5000 km/s, determined the wind's physical parameters.
Results
As a result, two statistically significant absorption lines were found at 7.6 and 9.8 keV (rest frame), corresponding to a blend of Fe XXV and Fe XXVI transitions. Doppler shifts indicated speeds of 0.09c and 0.33c. The slower component (UFO1) was present in both observation epochs, while the fast one (UFO2) appeared only in 2024, suggesting it is episodic. Mass outflow estimates are around 20 solar masses per year for each, about 15% of the accretion rate. The kinetic power of UFO2 reaches ~10^47 erg/s — roughly 10% of the bolometric luminosity. The continuum is notably soft (photon index Γ≈2) with a high-energy cutoff around 60-80 keV, corresponding to a corona electron temperature of ~15-20 keV (or ~200 million degrees). These parameters, including wind radii estimated from escape conditions (~123 and ~9 Schwarzschild radii, respectively), make this system a unique laboratory.
Implications
The results confirm theoretical models linking super-Eddington accretion with cool coronae and powerful winds, as predicted in particular by Jacob Bekenstein in the context of black hole thermodynamics. Finding a two-component wind with different temporal dynamics supports the idea of a magnetohydrodynamic 'spine-sheath' structure, where the faster wind is launched closer to the black hole. The fact that the kinetic power relative to luminosity follows the same dependence as in local Seyfert galaxies suggests the feedback mechanism is universal across cosmic history.
Future development
In the coming years, the WISSHFUL program will study 14 more similar quasars to build a statistical picture. High-sensitivity spectrometers on XRISM and the future NewAthena observatory (launching in the 2030s) will resolve the fine structure of winds, breaking the current degeneracy between density and ionization. This is critical for accurately calculating energetics and testing 'black box' feedback models.
Impact
The discovery impacts models of galaxy evolution, showing how accretion energy is transferred to the interstellar medium. It is also important for understanding the heating and entropy of gas in clusters, where such winds could explain observed distributions.
Next steps
The next step is to analyze the full WISSHFUL sample and compare with quasars at lower redshifts. High-resolution radio observations (VLBI) are also needed to check if some of the emission originates from a jet.
Key open problems
The work directly addresses a fundamental question: why do the masses of supermassive black holes correlate with the properties of galaxy bulges? Ultra-fast winds are a likely agent that 'shuts off' star formation, linking black hole and galaxy growth. Moreover, understanding accretion in extreme regimes is important for the dark matter problem, as feedback can shape density profiles in halo centers.
🎯 If UFO2 wind particles could fly in a straight line, they'd cover the Earth-Sun distance in just 1 hour and 20 minutes. By comparison, sunlight takes 8 minutes—but for matter, that's a mind-blowing speed.
🎬 The concept of ultra-fast winds steering a galaxy's fate recalls the 'Star Vortex' from Isaac Asimov's novels, where civilisations' evolution hinged on global energy flows.
Key numbers
- UFO2 Speed: 0.33c
- Mass Outflow (each component): ~20 M⊙/year
- Eddington Ratio: ~3
- Redshift: 3.294
- Corona Temperature: ~20 keV (~200 million K)