J/A+A/700/L8ivo://CDS.VizieR/J/A+A/700/L8doi:10.26093/cds/vizier.37009008CDSPozo Nunez. F.Banados E.Panda S.Heidt J.2025-08-27T20:01:27Z2025-08-06T12:20:43ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frquasarsinfrared-photometryPowered by supermassive black holes at their centers, quasars are among the most luminous objects in the universe, serving as important probes of cosmic history and galaxy evolution. The size of the accretion disc surrounding the black hole is a critical parameter for understanding quasar physics and their potential use as standard candles in cosmology. However, direct measurements of accretion disc sizes have so far been confined to the local universe (z<0.2), limiting our understanding of quasars during the peak of cosmic activity. Here we report the first direct measurement of the accretion disc size in the quasar QSO J0455-4216 at z=2.66, when the Universe was only ~2Gyrs old. Medium-band filters mounted on the MPG/ESO 2.2-metre telescope at La Silla Observatory were used to isolate continuum emission regions during a six-month monitoring campaign. The light curves exhibit pronounced variability features and enabled the detection of inter-band time delays from different parts of the disc. We map the disc and locate its ultraviolet-emitting outermost region at 3.02^+0.33^_-0.57_) light-days from the black hole (~500AU). Surrounding a supermassive black hole 900 million times the mass of the Sun, these measurements validate accretion disc theory at an unprecedented redshift and pave the way for efficient black hole mass estimates, reducing decades-long spectroscopic reverberation campaigns to just a few years or less.2025A&A...700L...8Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/700/L8CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/700/L8https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/700/L8http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/700/L8https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/700/L8https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/700/L8http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/700/L8GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapInfrareddefaultJ/A+A/700/L8/lcLight curves in 4 medium-bandsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMJD4858Observation date in filter 4858 (MJD - 60220)dtime.epochfloatF4858Normalized flux in filter 4858 (4858{AA})phot.flux;arith.ratiofloate_F48581{sigma} uncertainty in Flux 4858stat.errorfloatMJD5315Observation date in filter 5315 (MJD - 60220)dtime.epochfloatF5315Normalized flux in filter 5315 (5315{AA})phot.flux;arith.ratiofloate_F53151{sigma} uncertainty in Flux 5315stat.errorfloatMJD6043Observation date in filter 6043 (MJD - 60220)dtime.epochfloatF6043Normalized flux in filter 6043 (6043{AA})phot.flux;arith.ratiofloate_F60431{sigma} uncertainty in Flux 6043stat.errorfloatMJD7705Observation date in filter 7705 (MJD - 60220)dtime.epochfloatF7705Normalized flux in filter 7705 (7705{AA})phot.flux;arith.ratiofloate_F77051{sigma} uncertainty in Flux 7705stat.errorfloat