Measurements of the UV background at 4.6 < z < 6.4 using the quasar proximity effect

(2) Melbourne); Alexander P. Calverley (1); George D. Becker (1); James S. Bolton (2) ((1) KICC/IoA Cambridge; Martin G. Haehnelt (1)

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Measurements of the UV background at 4.6 < z < 6.4 using the quasar proximity effect

Alexander P. Calverley (1), George D. Becker (1), Martin G. Haehnelt (1), James S. Bolton (2) ((1) KICC/IoA Cambridge, (2) Melbourne)

Cosmology and Nongalactic Astrophysics · Submitted 26 Nov 2010

abstract compiled · 2026-09-23 · no language-model review

The authors' main claim We find a decline in Gamma_bkg with redshift, from log(Gamma_bkg) = -12.15 $\pm$ 0.16 at z ~ 5 to log(Gamma_bkg) = -12.84 $\pm$ 0.18 at z ~ 6 (1 sigma errors).

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arXiv ID1011.5850 (version 1)

Pith ID4KSOCPPN, Pith's permanent record of this paper and its review

Citation(2) Melbourne), Alexander P. Calverley (1), George D. Becker (1), James S. Bolton (2) ((1) KICC/IoA Cambridge, Martin G. Haehnelt (1). "Measurements of the UV background at 4.6 < z < 6.4 using the quasar proximity effect." arXiv:1011.5850 (2010). https://pith.science/paper/4KSOCPPN

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The paper's own sentences, arranged. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

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What the abstract itself states, as probabilities: claims first 0.87 · states limitation 0.96 · human participants 0.01 · controlled comparison 0.41 · randomized assignment 0.01 · states quantitative result 0.99 · compares with prior results 0.95 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; show every role.

We present measurements of the ionising ultraviolet background (UVB) at z ~ 5-6 using the quasar proximity effect. The fifteen quasars in our sample cover the range 4.6 < z_q < 6.4, enabling the first proximity effect measurements of the UVB at z > 5. The metagalactic hydrogen ionisation rate, Gamma_bkg, was determined by modelling the combined ionisation field from the quasar and the UVB in the proximity zone on a pixel-by-pixel basis. The optical depths in the spectra were corrected for the expected effect of the quasar until the mean flux in the proximity region equalled that in the average Ly-alpha forest, and from this we make a measurement of Gamma_bkg. A number of systematic effects were tested using synthetic spectra. Noise in the flux was found to be the largest source of bias at z ~ 5, while uncertainties in the mean transmitted Ly-alpha flux are responsible for the largest bias at z ~ 6. The impacts of large-scale overdensities and Lyman limit systems on Gamma_bkg were also investigated, but found to be small at z > 5. We find a decline in Gamma_bkg with redshift, from log(Gamma_bkg) = -12.15 $\pm$ 0.16 at z ~ 5 to log(Gamma_bkg) = -12.84 $\pm$ 0.18 at z ~ 6 (1 sigma errors). Compared to UVB measurements at lower redshifts, our measurements suggest a drop of a factor of five in the HI photoionisation rate between z ~ 4 and z ~ 6. The decline of Gamma_bkg appears to be gradual, and we find no evidence for a sudden change in the UVB at any redshift that would indicate a rapid change in the attenuation length of ionising photons. Combined with recent measurements of the evolution of the mean free path of ionising photons, our results imply decline in the emissivity of ionising photons by roughly a factor of two from z ~ 5 to 6, albeit with significant uncertainty due to the measurement errors in both Gamma_bkg and the mean free path.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	We present measurements of the ionising ultraviolet background (UVB) at z ~ 5-6 using the quasar proximity effect.	contribution 1.00	0.97	0.07	asserted 1.00
s1	The fifteen quasars in our sample cover the range 4.6 < z_q < 6.4, enabling the first proximity effect measurements of the UVB at z > 5.	contribution 0.72	0.93	0.04	asserted 1.00
s2	The metagalactic hydrogen ionisation rate, Gamma_bkg, was determined by modelling the combined ionisation field from the quasar and the UVB in the proximity zone on a pixel-by-pixel basis.	method 1.00	0.95	0.03	asserted 1.00
s3	The optical depths in the spectra were corrected for the expected effect of the quasar until the mean flux in the proximity region equalled that in the average Ly-alpha forest, and from this we make a measurement of Gamma_bkg.	method 1.00	0.96	0.04	asserted 1.00
s4	A number of systematic effects were tested using synthetic spectra.	method 0.98	0.91	0.01	asserted 0.94
s5	Noise in the flux was found to be the largest source of bias at z ~ 5, while uncertainties in the mean transmitted Ly-alpha flux are responsible for the largest bias at z ~ 6.	limitation 0.58	0.95	0.03	asserted 1.00
s6	The impacts of large-scale overdensities and Lyman limit systems on Gamma_bkg were also investigated, but found to be small at z > 5.	result 0.59	0.96	0.02	asserted 1.00
s7	We find a decline in Gamma_bkg with redshift, from log(Gamma_bkg) = -12.15 $\pm$ 0.16 at z ~ 5 to log(Gamma_bkg) = -12.84 $\pm$ 0.18 at z ~ 6 (1 sigma errors).	result 1.00	0.98	0.70	asserted 1.00
s8	Compared to UVB measurements at lower redshifts, our measurements suggest a drop of a factor of five in the HI photoionisation rate between z ~ 4 and z ~ 6.	result 0.51	0.79	0.22	hedged possibility 1.00
s9	The decline of Gamma_bkg appears to be gradual, and we find no evidence for a sudden change in the UVB at any redshift that would indicate a rapid change in the attenuation length of ionising photons.	result 0.73	0.96	0.15	asserted 0.99
s10	Combined with recent measurements of the evolution of the mean free path of ionising photons, our results imply decline in the emissivity of ionising photons by roughly a factor of two from z ~ 5 to 6, albeit with significant uncertainty due to the measurement errors in both Gamma_bkg and the mean free path.	interpretation 1.00	0.71	0.15	hedged possibility 0.83

What kind of paper the classifier reports this is: empirical study 1.00 · evidence from observation or experiment 0.60.

What was examined, and what was not

sources read

arXiv listing abstract v1

not examined

full text
figures and tables
references and citing sentences
relations to other papers

levels run

P abstract

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S sections
T body sentences
C citations
R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

The paper

Original abstract

We present measurements of the ionising ultraviolet background (UVB) at z ~ 5-6 using the quasar proximity effect. The fifteen quasars in our sample cover the range 4.6 < z_q < 6.4, enabling the first proximity effect measurements of the UVB at z > 5. The metagalactic hydrogen ionisation rate, Gamma_bkg, was determined by modelling the combined ionisation field from the quasar and the UVB in the proximity zone on a pixel-by-pixel basis. The optical depths in the spectra were corrected for the expected effect of the quasar until the mean flux in the proximity region equalled that in the average Ly-alpha forest, and from this we make a measurement of Gamma_bkg. A number of systematic effects were tested using synthetic spectra. Noise in the flux was found to be the largest source of bias at z ~ 5, while uncertainties in the mean transmitted Ly-alpha flux are responsible for the largest bias at z ~ 6. The impacts of large-scale overdensities and Lyman limit systems on Gamma_bkg were also investigated, but found to be small at z > 5. We find a decline in Gamma_bkg with redshift, from log(Gamma_bkg) = -12.15 $\pm$ 0.16 at z ~ 5 to log(Gamma_bkg) = -12.84 $\pm$ 0.18 at z ~ 6 (1 sigma errors). Compared to UVB measurements at lower redshifts, our measurements suggest a drop of a factor of five in the HI photoionisation rate between z ~ 4 and z ~ 6. The decline of Gamma_bkg appears to be gradual, and we find no evidence for a sudden change in the UVB at any redshift that would indicate a rapid change in the attenuation length of ionising photons. Combined with recent measurements of the evolution of the mean free path of ionising photons, our results imply decline in the emissivity of ionising photons by roughly a factor of two from z ~ 5 to 6, albeit with significant uncertainty due to the measurement errors in both Gamma_bkg and the mean free path.

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References

Forward citations

Cited by 5 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

specwizard: A Public Python Framework for Creating Synthetic Absorption Spectra from Hydrodynamical Simulations
astro-ph.CO 2026-10 accept novelty 6.0 of 10

specwizard is a publicly available Python framework that produces synthetic quasar absorption spectra from simulations, validated against Lyman-alpha forest observations.
SCRIPT in the Cosmic Dawn: Distinguishing Redshift-Evolving Galaxy Populations with 21-cm Fluctuations
astro-ph.CO 2026-08 conditional novelty 6.0 of 10

The 21-cm power spectrum, not the sky-averaged signal alone, can distinguish a redshift-evolving galaxy population from a static one during the cosmic dawn.
An emulator for the ionizing photon mean free path in ultra-high resolution simulations: the implications of mean free path measurements for the reionization history
astro-ph.CO 2026-02 conditional novelty 6.0 of 10

Photon mean-free-path observations at z≈5–6, interpreted with a neural-network emulator of high-resolution radiative-transfer simulations, favor a late, extended reionization with substantial neutral hydrogen persisti...
Sterile Neutrino Dark Matter
hep-ph 2018-07 accept novelty 3.0 of 10

Sterile neutrinos in the keV range remain a viable dark matter candidate, but the minimal version produced only by neutrino mixing is squeezed into a narrow, soon-testable window by X-ray and structure-formation data.
Galactic Outflows and Star-Formation Quenching: A JWST Perspective
astro-ph.GA 2026-10 accept novelty 2.0 of 10

JWST observations reveal that neutral outflows, traced by Si I D absorption, are present in 25-50% of massive galaxies at z~2 and are directly associated with rapid star-formation quenching.

How later papers used it

73 later papers cite it

Evidence: some. 55 of the citing papers share no author with it, and 22 of those carry a confident label from Pith's citation classifier.

Pith read 7 of the 97 citing sentences, choosing only those whose citation markers point at this paper alone, and wrote the paraphrases from them. The summary, the counts, the evidence level, the links and the quotes come from code; the summary counts the papers listed below. A later paper is listed under a label when Pith's citation classifier gives one of its sentences that label at probability 0.8 or more (0.95 for support), Pith's reading finds that the citing paper itself did it, and a second check confirms the paraphrase against the sentence. This section lists uses only. It does not list criticism or disagreement, so their absence here says nothing about how the paper has been received. Papers that share an author with this one are listed apart, under "By the same authors". A quote is the citing authors' own sentence, shown when their paper's licence is CC BY, CC BY-SA or CC0. JSON

2 later papers by other authors are listed below: 2 used its data or values. 1 more paper by the same authors is listed: 1 used its method or tool.

Uses its method or tool 1 of 3 papers with this label · 1 by the same authors

By the same authors

Following [ref] , $R_eq$ is related to $Γ_bg$ and the ionizing luminosity of the QSO, $L_912$, by [equation] where $σ_0$ and $α_ν^ion$ are the ionization cross section at 912 Å and the power-law index of the QSO continuum at $λ<912$ Å in the frequency domain, respectively, and $ħ$ is the reduced Planck constant. $L_912$ can be further related to the absolute magnitude corresponding the the mean luminosity at rest-frame 1450 Å, $L_1450$, by $L_912=L_1450(ν_912/ν_1450)^-α_ν^UV$.

Probing Ultra-late Reionization: Direct Measurements of the Mean Free Path over $5<z<6$ (2023) (same authors) · Methods · 0.98

Uses its data or values 2 of 10 papers with this label

Used this paper's Gamma_HI measurements at z > 5 in its UVB calculations.

Constraints on QSO emissivity using H I and He II Lyman alpha forest (2017) · 1.00 · paraphrased: the licence does not allow quoting
Used the measurements this paper obtained from proximity zones of high-z QSOs at z = 5 and 6.1.

New synthesis models of consistent extragalactic background light over cosmic time (2018) · 1.00 · paraphrased: the licence does not allow quoting

How the literature uses it

6 arXiv papers cite this in 7 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 5 sentences without a confident label

Uses its data or values 1 paper

The photoionization rate measurements are compiled from [ref] , [ref] , [ref] , [ref] , and [ref] .[For reproducibility, the adopted $Γ_-12$ values (in units of $10^-12$ s$^-1$, prioritizing the most recent studies) are: $z=4.8$: $0.58^+0.08_-0.20$; $z=4.9$: $0.501^+0.275_-0.232$; $z=5.0$: $0.557^+0.376_-0.218$; $z=5.1$: $0.508^+0.324_-0.192$; $z=5.2$: $0.502^+0.292_-0.193$; $z=5.3$: $0.404^+0.272_-0.147$; $z=5.4$: $0.372^+0.217_-0.126$; $z=5.5$: $0.344^+0.219_-0.130$; $z=5.6$: $0.319^+0.194_-0.120$; $z=5.7$: $0.224^+0.223_-0.112$; $z=5.8$: $0.178^+0.194_-0.078$; $z=5.9$: $0.151^+0.151_-0.079$; $z=6.0$: $0.145^+0.157_-0.087$.] Since this specifies $Γ_-12$, the emulator can then predict the MFP with redshift given a model for $Q(z)$.

An emulator for the ionizing photon mean free path in ultra-high resolution simulations: the implications of mean free path measurements for the reionization history · Mean Free Path Predictions for Patchy Reionization · 1.00

Cites it as background 1 paper

Statistics of the scarce transmitted flux in the forest are being combined with insights from quasar proximity zones to learn about the very high-redshift IGM [ref] .

High-Redshift Metals. II. Probing Reionization Galaxies with Low-Ionization Absorption Lines at Redshift Six · Introduction · 0.92

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