Journal
ASTROPHYSICAL JOURNAL
Volume 923, Issue 2, Pages -Publisher
IOP Publishing Ltd
DOI: 10.3847/1538-4357/ac26c2
Keywords
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Categories
Funding
- National Science Foundation [AST-1615814, AST1751404]
- National Science Foundation Graduate Research Fellowship Program [DGE-1326120]
- European Research Council (ERC) [740246]
- European Union [885990]
- Australian Research Council [DP190100252]
- Chinese Academy of Sciences (CAS) [CCJRF1809]
- NASA - Space Telescope Science Institute [HF251434, HST-HF2-51448.001-A]
- NASA [NAS526555]
- NSF [AST 15-15115, AST 19-08284]
- UKRI STFC [ST/N000927/1, ST/S000623/1]
- Max Planck Society
- ERC [INTERSTELLAR H2020/740120]
- Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) [CE170100013]
- National Aeronautics and Space Administration
- BEIS capital funding via STFC [ST/P002307/1, ST/R002452/1, ST/P002293/1, ST/R002371/1]
- STFC [ST/R00689X/1, ST/R000832/1]
- Durham University
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Researchers conducted a new investigation of the intergalactic medium near the end of reionization using dark gaps in the Ly alpha forest. They identified nine ultralong dark gaps at z<6 and measured the fraction of these gaps at different redshifts. The results suggest that signatures of reionization remain present in the intergalactic medium until at least z≈5.3.
We present a new investigation of the intergalactic medium (IGM) near the end of reionization using dark gaps in the Ly alpha forest. Using spectra of 55 QSOs at z (em) > 5.5, including new data from the XQR-30 VLT Large Programme, we identify gaps in the Ly alpha forest where the transmission averaged over 1 comoving h (-1) Mpc bins falls below 5%. Nine ultralong (L > 80 h (-1) Mpc) dark gaps are identified at z < 6. In addition, we quantify the fraction of QSO spectra exhibiting gaps longer than 30 h (-1) Mpc, F (30), as a function of redshift. We measure F (30) similar or equal to 0.9, 0.6, and 0.15 at z = 6.0, 5.8, and 5.6, respectively, with the last of these long dark gaps persisting down to z similar or equal to 5.3. Comparing our results with predictions from hydrodynamical simulations, we find that the data are consistent with models wherein reionization extends significantly below redshift six. Models wherein the IGM is essentially fully reionized that retain large-scale fluctuations in the ionizing UV background at z less than or similar to 6 are also potentially consistent with the data. Overall, our results suggest that signatures of reionization in the form of islands of neutral hydrogen and/or large-scale fluctuations in the ionizing background remain present in the IGM until at least z similar or equal to 5.3.
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