An extremely high-velocity outflow in SMSS J2157-3602, the most luminous quasar in the first 1.3 Gyr
We report the discovery of an extremely high-velocity outflow (EHVO) in the most luminous QSO ( L Bol ∼ 2.29 × 10 48 erg/s), named SMSS J2157-3602, at z = 4.692. Combined XSHOOTER and NIRES observations reveal that the EHVO reaches a maximum velocity of v max ∼ 0.13 c and persists over rest-frame timescales of a few months up to one year. SMSS J2157-3602 also exhibits one of the highest balnicity index values discovered for an EHVO so far. In addition, the blueshifted CIV emission traces a high-velocity ( v CIV 50 ∼ 4660 km/s) outflow from the broad-line region (BLR). Thanks to an XMM-Newton observation, we were also able to reveal the X-ray weak nature of this QSO, which likely prevents the overionization of the innermost disk atmosphere and facilitates the efficient launch of the detected EHVO and BLR winds. The extraordinary luminosity of SMSS J2157-3602 and the extreme velocity of the EHVO make it a unique laboratory for testing active galactic nucleus (AGN) driven feedback under extreme conditions. Current uncertainties on the outflow’s location and column density strengthen the case for a dedicated follow-up, which will be essential to assess the full feedback potential of this remarkable quasar.
Authors
- A. Melandri (ORCID: https://orcid.org/0000-0002-2810-2143)
- Liliana Flores (ORCID: https://orcid.org/0000-0003-3550-4340)
- E. Piconcelli (ORCID: https://orcid.org/0000-0001-9095-2782)
- G. Lanzuisi (ORCID: https://orcid.org/0000-0001-9094-0984)
- Christian Wolf (ORCID: https://orcid.org/0000-0002-4569-016X)
- Toru Misawa (ORCID: https://orcid.org/0000-0002-5464-9943)
- Patrick B. Hall (ORCID: https://orcid.org/0000-0002-1763-5825)
- C. Vignali (ORCID: https://orcid.org/0000-0002-8853-9611)
- G. Vietri (ORCID: https://orcid.org/0000-0001-9155-8875)
- Amy L. Rankine (ORCID: https://orcid.org/0000-0002-2091-1966)
- V. Testa (ORCID: https://orcid.org/0000-0003-1033-1340)
- Christopher A. Onken (ORCID: https://orcid.org/0000-0003-0017-349X)
- L. Zappacosta (ORCID: https://orcid.org/0000-0002-4205-6884)
- V. D’Odorico (ORCID: https://orcid.org/0000-0003-3693-3091)
- Paola Rodríguez Hidalgo (ORCID: https://orcid.org/0000-0003-0677-785X)
- I. Saccheo (ORCID: https://orcid.org/0000-0003-1174-6978)
- Flaminia Sarnari (ORCID: https://orcid.org/0009-0008-6212-2608)
Institutions
- Australian National University (AU)
- Shinshu University (JP)
- York University (CA)
- Astronomical Observatory of Rome (IT)
- Trieste Astronomical Observatory (IT)
- University of Bristol (GB)
- Osservatorio astronomico di Bologna (IT)
- Royal Observatory (GB)
- Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano (IT)
- ARC Centre of Excellence for Gravitational Wave Discovery (AU)
- University of Washington Bothell (US)
- Institute for Fundamental Physics of the Universe (IT)
- Bristol Robotics Laboratory (GB)
- Osservatorio di Astrofisica e Scienza dello Spazio
- Sapienza University of Rome (IT)
- National Institute for Astrophysics (IT)
- University of Bologna (IT)
- University of Edinburgh (GB)
Publication Details
- Journal
- Astronomy and Astrophysics
- Published
- 2025-12-01
- DOI
- https://doi.org/10.1051/0004-6361/202555673
- Citations
- 1
- Primary Topic
- Galaxies: Formation, Evolution, Phenomena
- Type
- article
- Field-Weighted Citation Impact
- 1.15
Funders
- National Science Foundation
- Alfred P. Sloan Foundation
- UK Research and Innovation
- European Commission
- European Southern Observatory
- Japan Society for the Promotion of Science