Swift Outflow from Quasar J2318: Relativistic Wind at 0.3c ✦

Original: "A New Member of the Fast and Furious Family: A Relativistic and Time-Variable UV Outflow in a Luminous Quasar"

arXiv:2606.06226v1 · 2026-06-04 · CC BY 4.0 · ⏱ 3 min · Galaxies

Astronomers have discovered the fastest ultraviolet outflow in quasar J2318, reaching nearly a third of the speed of light.

Abstract

We present the fastest known quasar outflow, discovered in the ultraviolet via variable absorption of C IV and Si IV ions at velocities from −77,000 to −90,000 km/s (≈0.3c) in the radio-quiet quasar SDSS J2318. Gemini GNIRS spectroscopy of the Hα line gives a redshift of z=2.6781; 20-year photometry shows peak variability of 0.5 mag in the g-band. Over ~2.2 years in the rest frame, C IV absorption increased monotonically. The existence of this outflow requires models that either accelerate gas to 0.3c while retaining C IV and Si IV, or produce these ions in situ within the already fast-moving gas. The virial black hole mass is 1.65×10⁹ M☉, with an Eddington ratio of 0.45. Under conservative assumptions, the mass-loss rate in the UV outflow alone exceeds 0.82 M☉/yr, and the ratio of kinetic to bolometric luminosity L_kin/L_bol ≥ 0.75%, exceeding the threshold for significant galactic feedback. Comparison with PDS 456 suggests these values could be two orders of magnitude higher.

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Context

Back in the mid-20th century, Maarten Schmidt identified quasars as distant active galactic nuclei. Today we know that at the heart of every quasar lies a supermassive black hole actively devouring matter. Yet some of the gas doesn't fall into the abyss but is flung outward in powerful outflows that can affect the entire host galaxy — heating and sweeping away interstellar medium, regulating star formation. Observing these 'winds' is key to understanding the co-evolution of black holes and their galaxies.

Methods

The discovery was made possible by years of spectroscopic monitoring as part of the Sloan Digital Sky Survey (SDSS) and observations with the Gemini North telescope. Spectra of the quasar, obtained in three epochs, showed deep absorption troughs in the ultraviolet. To isolate the absorption lines, researchers built continuum models corrected for interstellar reddening and Lyman-alpha forest suppression. Both direct integration and Gaussian fitting were applied. Light curves from ground-based surveys complemented the variability picture.

Results

The absorption lines of carbon CIV and silicon SiIV ions were blueshifted by a staggering 77,000–90,000 km/s, about 0.3 of the speed of light. This is the second known quasar with such a fast ultraviolet outflow after PDS 456. Over 2.2 years (in the quasar's rest frame), the outflow monotonically increased: the equivalent width of the CIV line grew from 660 to 3,730 km/s. Virial estimates from the Hα line gave a black hole mass of 1.65×10^9 M⊙, and the bolometric luminosity reached 1.09×10^47 erg/s with an Eddington ratio of about 0.45. The lower limit on the mass loss rate is 0.82 M⊙ per year, corresponding to a kinetic luminosity of at least 0.75% of the Eddington luminosity.

Implications

Such powerful feedback places J2318 among objects where the outflow feedback can significantly impact the galaxy. This supports theoretical models that require 'winds' from active nuclei to explain black hole mass–bulge property relations. Moreover, the presence of low-ionization ions at such high speeds challenges acceleration theories: the gas must either accelerate without overheating, or it must form already in the flowing stream.

Future development

Further monitoring of J2318, including X-ray observations with future observatories like NewAthena, will probe hotter phases of the outflow. Instruments like James Webb can detect molecular wind components. Growing the sample of extreme outflows will help determine whether a speed of ~0.3c is a universal limit, perhaps tied to the 'trapping' mechanism of Lyman-series lines.

Impact

The results are important for understanding the evolution of massive galaxies in the early Universe, where quasars are especially active. They also spur the development of hydrodynamic simulations with feedback.

Next steps

Plans are to continue spectroscopic monitoring to track absorption variability, and to obtain deep X-ray spectra to determine the total column density and outflow energy.

Key open problems

The puzzle of gas acceleration in quasar outflows remains unsolved. How gas survives in a low-ionization state while being accelerated to 0.3c is a question that connects to the problem of shock waves and thermal conduction in astrophysical plasmas. Moreover, the link between ultraviolet and X-ray outflow components is critical for estimating the total feedback budget.

🎯 If the wind from J2318 were blowing through the Solar System, it would travel the distance from Earth to the Moon in less than 4 seconds. The quasar itself is 'weak-lined', its emission lines anomalously faint, making it resemble an astrophysical 'quiet one' with a wild temper.

M_{\rm BH} = A \left( \frac{L_{5100}}{10^{44}\,{\rm erg/s}} \right)^b \left( \frac{{\rm FWHM}_{\rm H\alpha}}{v_{\rm norm}} \right)^c

Empirical calibration linking black hole mass to continuum luminosity and emission line width.

L_{\rm Edd} = \frac{4\pi G M_{\rm BH} \mu m_p c}{\sigma_{\rm T}}

Maximum luminosity at which radiation pressure balances gravity for ionized gas.

\dot{M} > N_{\rm H} \, \mu m_p \, 4\pi \Omega R v

Minimum mass loss rate estimated assuming unsaturated absorption and full coverage of the emission source.

Key numbers

Outflow speed: up to 90,000 km/s (≈0.3c)
Black hole mass: 1.65 × 10^9 M⊙
Mass loss rate: >0.82 M⊙/yr
Energy feedback (L_kin/L_Edd): >0.75%
Redshift: z = 2.6781

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