J/A+A/705/A114ivo://CDS.VizieR/J/A+A/705/A114CDSMason C.A.Chen Z.Stark D.P.Lu T.-Y.Topping M.Tang M.2026-03-02T06:25:50Z2026-01-12T09:07:32ZCDS support team

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

cds-question@unistra.frgalaxiesredshiftedultraviolet-photometryJWST provides a unique dataset for studying the earliest stages of reionisation at z>9, promising insights into the first galaxies. Many JWST/NIRSpec prism spectra of z>5 galaxies have revealed smooth Lyman-alpha breaks, implying damping wing scattering by neutral hydrogen. We investigate what current prism spectra imply about the intergalactic medium (IGM) at z>6 and how best to use NIRSpec spectra to recover IGM properties. We use a sample of 99 z~5.5-13 galaxies with high S/N prism spectra in the public archive, including 12 at z>10. We analyse these spectra using damping wing sightlines from inhomogeneous reionising IGM simulations, mapping between the distance of a source from the neutral IGM and the average IGM neutral fraction. We marginalise over absorption by local neutral hydrogen around the galaxies and Lyman-alpha emission. We observe a decline in the median and variance of flux around the Ly{alpha} break with increasing redshift, consistent with an increasingly neutral IGM, as ionized regions become smaller and rarer. At z>~9 the spectra become consistent with an almost fully neutral IGM. We find S/N > 15 per pixel is required to robustly estimate IGM properties from prism spectra. We fit a sub-sample of high S/N spectra and infer mean IGM neutral fractions of X{bar}HI=0.33_-0.27_^+0.18^, 0.64_-0.23_^+0.17^ (>0.70 excluding GNz11) at z~=6.5, 9.3. We also investigate local HI absorption, finding a median column density of log10NHI~=10^20.8^cm^-2^, comparable to z~3 Lyman-break galaxies, with no significant redshift evolution z>~5.5. We find galaxies showing the highest column density absorption are more likely to be in close associations of sources (<~500pkpc), implying absorption is enhanced in massive dark matter halos. Future deep prism and grating spectroscopy of z>9 sources will provide tighter constraints on the earliest stages of reionisation, key for understanding the onset of star formation.2026A&A...705A.114Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/705/A114CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/705/A114https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/705/A114http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/705/A114https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/705/A114https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/705/A114http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/705/A114GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/705/A114/tablef1 (Source catalog)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/705/A114/tablef1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/705/A114/tablef1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/705/A114/tablef1?GETtext/xml+votable180.050000true214.768356252.71764170.0055555555555555566/11252 11425 16486 35935https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/705/A114?format=asciiUVdefaultJ/A+A/705/A114/tablef1Source catalogrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDSource identifiermeta.id;meta.maincharRAJ2000Right Ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainzspSpectroscopic redshiftsrc.redshiftfloatUVMAGAbsolute UV magnitude, corrected for magnificationmagphys.magAbsfloate_UVMAGLower uncertainty on MUV (1{sigma})magstat.errorfloatE_UVMAGUpper uncertainty on MUV (1{sigma})magstat.error;stat.maxfloatFlag[1/2]? Optional flag (1)meta.code.errorintnullable