George D. Becker, Max Pettini, Marc Rafelski, Elisa Boera, Lise Christensen, Guido Cupani, Sara L. Ellison, Emanuele Paolo Farina, Michele Fumagalli, Sebastian Lopez, Marcel Neeleman, Emma Ryan-Weber, Gabor Worseck
- We present a survey for metal absorption systems traced by neutral oxygen over 3.2 < z < 6.5. Our survey uses Keck/ESI and VLT/X-Shooter spectra of 199 QSOs with redshifts up to 6.6. In total, we detect 74 OI absorbers, of which 57 are separated from the background QSO by more than 5000 km s(-1). We use a maximum likelihood approach to fit the distribution of OI lambda 1302 equivalent widths in bins of redshift and from this determine the evolution in number density of absorbers with W-1302 > 0.05 angstrom, of which there are 49 nonproximate systems in our sample. We find that the number density does not monotonically increase with decreasing redshift, as would naively be expected from the buildup of metal-enriched circumgalactic gas with time. The number density over 4.9 < z < 5.7 is a factor of 1.7-4.1 lower (68% confidence) than that over 5.7 < z < 6.5, with a lower value at z < 5.7 favored with 99% confidence. This decrease suggests that the fraction of metals in a low-ionization phase is larger at z similar to 6 than at lowerWe present a survey for metal absorption systems traced by neutral oxygen over 3.2 < z < 6.5. Our survey uses Keck/ESI and VLT/X-Shooter spectra of 199 QSOs with redshifts up to 6.6. In total, we detect 74 OI absorbers, of which 57 are separated from the background QSO by more than 5000 km s(-1). We use a maximum likelihood approach to fit the distribution of OI lambda 1302 equivalent widths in bins of redshift and from this determine the evolution in number density of absorbers with W-1302 > 0.05 angstrom, of which there are 49 nonproximate systems in our sample. We find that the number density does not monotonically increase with decreasing redshift, as would naively be expected from the buildup of metal-enriched circumgalactic gas with time. The number density over 4.9 < z < 5.7 is a factor of 1.7-4.1 lower (68% confidence) than that over 5.7 < z < 6.5, with a lower value at z < 5.7 favored with 99% confidence. This decrease suggests that the fraction of metals in a low-ionization phase is larger at z similar to 6 than at lower redshifts. Absorption from highly ionized metals traced by CIV is also weaker in higher-redshift OI systems, supporting this picture. The evolution of OI absorbers implies that metal-enriched circumgalactic gas at z similar to 6 is undergoing an ionization transition driven by a strengthening ultraviolet background. This in turn suggests that the reionization of the diffuse intergalactic medium may still be ongoing at or only recently ended by this epoch.…
MetadatenAuthor details: | George D. BeckerORCiD, Max PettiniORCiD, Marc RafelskiORCiD, Elisa BoeraORCiD, Lise ChristensenORCiD, Guido CupaniORCiD, Sara L. EllisonORCiD, Emanuele Paolo FarinaORCiD, Michele FumagalliORCiD, Sebastian LopezORCiD, Marcel NeelemanORCiD, Emma Ryan-WeberORCiD, Gabor WorseckORCiD |
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DOI: | https://doi.org/10.3847/1538-4357/ab3eb5 |
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ISSN: | 0004-637X |
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ISSN: | 1538-4357 |
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Title of parent work (English): | The astrophysical journal : an international review of spectroscopy and astronomical physics |
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Publisher: | IOP Publ. Ltd. |
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Place of publishing: | Bristol |
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Publication type: | Article |
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Language: | English |
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Date of first publication: | 2019/10/01 |
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Publication year: | 2019 |
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Release date: | 2020/12/07 |
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Volume: | 883 |
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Issue: | 2 |
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Number of pages: | 37 |
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Funding institution: | National Science FoundationNational Science Foundation (NSF) [AST-1615814, AST-1751404]; Independent Research Fund Denmark [DFF 4090-00079]; Science and Technology Facilities CouncilScience & Technology Facilities Council (STFC) [ST/P000541/1]; European Research Council (ERC) under the European UnionEuropean Research Council (ERC) [757535]; FONDECYTComision Nacional de Investigacion Cientifica y Tecnologica (CONICYT)CONICYT FONDECYT [1191232]; ERCEuropean Research Council (ERC) [740246]; Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D)Australian Research Council [CE170100013]; W.M. Keck FoundationW.M. Keck Foundation; National Aeronautics and Space AdministrationNational Aeronautics & Space Administration (NASA); [UCh/VID-ENL18/18]; [060.A-9024]; [084.A-0360]; [084.A-0390]; [084.A-0550]; [085.A-0299]; [086.A-0162]; [086.A-0574]; [087.A-0607]; [087.A-0890]; [088.A-0897]; [091.C-0934]; [096.A-0095]; [096.A-0418]; [097.B1070]; [098.A-0111]; [098.B-0537]; [0100.A-0243]; [0100.A-0625]; [0102.A-0154]; [189.A-0424]; [294.A-5031] |
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Organizational units: | Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie |
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DDC classification: | 5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik |
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Peer review: | Referiert |
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Publishing method: | Open Access / Green Open-Access |
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