Quasar radiation transforms the gas in a merging companion galaxy

Abstract

Quasars, powered by gas accretion onto supermassive black holes, rank among the most energetic objects of the Universe. While they are thought to be ignited by galaxy mergers and affect the surrounding gas, observational constraints on both processes remain scarce. Here we unveil a major merging system at redshift $z\approx 2.7$, and demonstrate that radiation from the quasar in one galaxy directly alters the gas properties in the other galaxy. Our findings reveal that the galaxies, with centroids separated by only a few kiloparsecs and approaching each other at speed $\approx 550$kms${}^{-1}$, are massive, form stars, and contain a substantial molecular mass. Yet, dusty molecular gas seen in absorption against the quasar nucleus is highly excited and confined within cloudlets with densities $\sim 10^5$ - $10^6$ cm${}^{-3}$ and sizes $<$0.02 pc, several orders of magnitude more compact than those observed in intervening (non-quasar) environments. This is also approximately 10${}^5$ times smaller than currently resolvable through molecular-line emission at high redshifts. We infer that, wherever exposed to the quasar radiation, molecular gas is disrupted, leaving behind surviving dense clouds too small to give birth to new stars. Our results not only underscore the role of major galaxy mergers in triggering quasar activity, but also reveal localized negative feedback as a profound alteration of internal gas structure which likely hampers star formation.

28 pages, 12 figures, published in Nature on May 21th, 2025, https://www.nature.com/articles/s41586-025-08966-4

References in corpus (41)

• Array Programming with NumPy
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• A Cosmological Framework for the Co-Evolution of Quasars, Supermassive Black Holes, and Elliptical Galaxies: I. Galaxy Mergers & Quasar Activity
• An ultra-luminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30
• The Main Sequence of star-forming galaxies across cosmic times
• Evidence for Quasar Activity Triggered by Galaxy Mergers in HST Observations of Dust-reddened Quasars
• SoFiA: a flexible source finder for 3D spectral line data
• Velocity-Metallicity Correlation for high-z DLA Galaxies: Evidence for a Mass-Metallicity Relation?
• HI-to-H2 Transitions and H I Column Densities in Galaxy Star-Forming Regions
• Rapidly star-forming galaxies adjacent to quasars at redshifts exceeding 6
• Galaxy Interactions Trigger Rapid Black Hole Growth: an unprecedented view from the Hyper Suprime-Cam Survey
• SoFiA 2 -- An automated, parallel HI source finding pipeline for the WALLABY survey
• ALMA Observations Show Major Mergers Among the Host Galaxies of Fast-growing, High-redshift Supermassive Black Holes
• How to quench a galaxy
• The ALMA Spectroscopic Survey in the HUDF: CO Excitation and Atomic Carbon in Star-Forming Galaxies at $z=1-3$
• Extremely Red Quasars in BOSS
• The Scaling of Stellar Mass and Central Stellar Velocity Dispersion for Quiescent galaxies at z < 0.7
• A connection between extremely strong Damped Lyman-alpha Systems and Lyman-alpha Emitting Galaxies at small impact parameters
• Discovery of a Perseus-like cloud in the early Universe: HI-to-H2 transition, carbon monoxide and small dust grains at zabs=2.53 towards the quasar J0000+0048
• Excitation mechanisms in newly discovered H2-bearing Damped Lyman-alpha clouds: systems with low molecular fractions
• Detection of the 2175Å~ extinction feature and 21-cm absorption in two MgII systems at z~1.3
• CO-dark molecular gas at high redshift: very large H${}_2$ content and high pressure in a low metallicity damped Lyman-alpha system
• The ALMA Interferometric Pipeline Heuristics
• A Far Ultraviolet Spectroscopic Explorer Survey of Interstellar Molecular Hydrogen in the Galactic Disk
• X-shooter observations of strong H${}_2$-bearing DLAs at high redshift
• Proximate Molecular Quasar Absorbers: Excess of damped H2 systems at zabs~zQSO in SDSS DR14
• Directional Radiation and Photodissociation Regions in Molecular Hydrogen Clouds
• The accretion of a solar mass per day by a 17-billion solar mass black hole
• SMM J04135+10277: A distant QSO-starburst system caught by ALMA
• High-redshift Damped Ly-alpha Absorbing Galaxy Model Reproducing the N(HI)-Z Distribution
• Physical conditions in diffuse interstellar medium of local and high redshift galaxies: measurements based on excitation of H${}_2$ rotational and CI fine-structure levels
• Hyper Suprime-Cam Legacy Archive
• HD molecules at high redshift: cosmic-ray ionization rate in the diffuse interstellar medium
• Down-the-barrel observations of a multiphase quasar outflow at high redshift: VLT/X-shooter spectroscopy of the proximate molecular absorber at z=2.631 towards SDSS J001514+184212
• Seven broad absorption line quasars with excess broad band absorption near 2250 Å
• Extent and structure of intervening absorbers from absorption lines redshifted on quasar emission lines
• Major Mergers Host the Most Luminous Red Quasars at z ~ 2: A Hubble Space Telescope WFC3/IR Study
• Proximate molecular quasar absorbers: Chemical enrichment and kinematics of the neutral gas
• Neutral carbon in diffuse interstellar medium: abundance matching with H2 for DLAs at high redshifts
• Molecular hydrogen in absorption at high redshifts. Science cases for CUBES

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• An ALMA Band 7 survey of SDSS/Herschel quasars in Stripe 82: I. The properties of the 870 micron counterparts
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