Cosmic Reionization on Computers: Statistical Properties of the Distributions of Mean Opacities

Journal Article · Thu Mar 13 04:00:00 EDT 2025 · TBD

OSTI ID:2551806

Werre, Ella ^[1]; Robinson, David ^[2]; Avestruz, Camille ^[2]; Gnedin, Nickolay Y. ^[3]

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1. Michigan U.; Michigan State U.
2. U. Michigan, Ann Arbor; Michigan U., LCTP
3. Fermilab; Chicago U., KICP; Chicago U., Astron. Astrophys. Ctr.

Quasar absorption lines provide a unique window to the relationship between galaxies and the intergalactic medium during the Epoch of Reionization. In particular, high redshift quasars enable measurements of the neutral hydrogen content of the universe. However, the limited sample size of observed quasar spectra, particularly at the highest redshifts, hampers our ability to fully characterize the intergalactic medium during this epoch from observations alone. In this work, we characterize the distributions of mean opacities of the intergalactic medium in simulations from the Cosmic Reionization on Computers (CROC) project. We find that the distribution of mean opacities along sightlines follows a non-trivial distribution that cannot be easily approximated by a known distribution. When comparing the cumulative distribution function of mean opacities measurements in subsamples of sample sizes similar to observational measurements from the literature, we find consistency between CROC and observations at redshifts $$z\lesssim 5.7$$. However, at higher redshifts ($$z\gtrsim5.7$$), the cumulative distribution function of mean opacities from CROC is notably narrower than those from observed quasar sightlines implying that observations probe a systematically more opaque intergalactic medium at higher redshifts than the intergalactic medium in CROC boxes at these same redshifts. This is consistent with previous analyses that indicate that the universe is reionized too early in CROC simulations.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
• DOE Contract Number: 89243024CSC000002
• OSTI ID: 2551806
• Report Number(s): FERMILAB-PUB-25-0172-T; arXiv:2503.10768; oai:inspirehep.net:2900556
• Journal Information: TBD, Journal Name: TBD
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS