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SHELLQs. Black Hole Mass and Eddington Ratio Distributions of Intermediate-Luminosity Quasars at 6<z<7

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ReviewThe objections and verdict, as JSON Paper breakdownThe authors' claims, conditions and measurements, as JSON Signed receiptProof this review has not been altered
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Masafusa Onoue, John D. Silverman, Yoshiki Matsuoka, Xuheng Ding, Camryn L. Phillips, Michael A. Strauss, Junya Arita, Takuma Izumi
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Mahoshi Sawamura, Nobunari Kashikawa, Irham Andika, Kentaro Aoki, Shunsuke Baba, Anna-Christina Eilers, Seiji Fujimoto, Tomotsugu Goto, Masatoshi Imanishi, Kohei Inayoshi, Kazushi Iwasawa, Knud Jahnke, Yuki Kaneko, Toshihiro Kawaguchi, Kotaro Kohno, Chien-Hsiu Lee, Alessandro Lupi, Tohru Nagao, Dragan Salak, Malte Schramm, Yoshiki Toba, Hideki Umehata, Marta Volonteri, Fabian Walter, Feige Wang, Jinyi Yang

Astrophysics of Galaxies · Submitted 8 Sep 2026 · 259 references

Pith's verdict: Solid data and careful spectral fitting, but the key population comparison mixes two different mass estimators without cross-calibration, so the claimed -0.4 dex offset and super-Eddington fraction should be taken with a grain of salt.

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arXiv ID2609.09266 (version 1)
Pith IDJ3PHN7CG, Pith's permanent record of this paper and its review
CitationAlessandro Lupi, Anna-Christina Eilers, Camryn L. Phillips, Chien-Hsiu Lee, Dragan Salak, Fabian Walter, Feige Wang, Hideki Umehata, Irham Andika, Jinyi Yang, John D. Silverman, Junya Arita, Kazushi Iwasawa, Kentaro Aoki, Knud Jahnke, Kohei Inayoshi, Kotaro Kohno, Mahoshi Sawamura, Malte Schramm, Marta Volonteri, Masafusa Onoue, Masatoshi Imanishi, Michael A. Strauss, Nobunari Kashikawa, Seiji Fujimoto, Shunsuke Baba, Takuma Izumi, Tohru Nagao, Tomotsugu Goto, Toshihiro Kawaguchi, Xuheng Ding, Yoshiki Matsuoka, Yoshiki Toba, Yuki Kaneko. "SHELLQs. Black Hole Mass and Eddington Ratio Distributions of Intermediate-Luminosity Quasars at 6<z<7." arXiv:2609.09266 (2026). https://pith.science/paper/J3PHN7CG
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The paper

The paper claims

Intermediate-luminosity quasars at z~6-7 have systematically smaller black holes and higher accretion rates than their low-redshift counterparts, with up to 22% accreting at super-Eddington rates.

The reading

The paper assembles a sample of 27 quasars at redshift 6 to 7 from the SHELLQs project, using JWST and Subaru spectroscopy to measure black hole masses via broad emission lines. It finds a median mass of about 400 million solar masses and a median Eddington ratio of 0.23. Compared to luminosity-matched quasars at z~1.3, the high-redshift sample shows black hole masses 0.4 dex lower and Eddington ratios 0.2 dex higher. Moreover, 11-22% of these early quasars accrete at or above the Eddington limit, suggesting that rapid accretion is common during the first billion years. This extends the anti-hierarchical (downsizing) growth scenario to a more representative population.

What carries the argument

The single-epoch virial black hole mass estimator, which uses the width of broad emission lines (Balmer lines from JWST/NIRSpec; MgII from Subaru/MOIRCS) as a proxy for virial velocity, and the continuum luminosity to infer the broad-line region radius via the locally calibrated R_BLR–luminosity relation (R_BLR ∝ $L^{0}$.5). The geometric factor f is assumed to be the same as in the local universe.

Extended reading notes

Core claim

The central discovery is that intermediate-luminosity quasars at 6<z<7 — a regime bridging luminous quasars and faint JWST AGN — have a median black hole mass of log(M_BH/M⊙)=8.6 and median Eddington ratio log(L_bol/L_Edd)=-0.63. When matched in bolometric luminosity to SDSS quasars at z≈1.3, the high-redshift sample shows median offsets of Δlog M_BH = -0.4 dex and Δlog L_bol/L_Edd = +0.2 dex. Furthermore, 11% (rising to 22% under an Eddington-ratio-dependent mass calibration) of the high-redshift quasars accrete near or above the Eddington limit, indicating that a significant fraction of early supermassive black holes undergo a rapid growth phase.

Load-bearing premise

The locally calibrated single-epoch black hole mass estimator, which assumes the broad-line region size scales as luminosity to the 0.5 power and uses a geometric factor f that encodes BLR geometry and kinematics, applies without redshift evolution at z~6.

Editorial extensions

If this is right

  • A significant fraction of supermassive black holes in the reionization epoch grow through near- or super-Eddington accretion episodes, which must be accounted for in models of early black hole formation and growth.
  • The observed anti-hierarchical trend (lower masses, higher Eddington ratios at higher redshift) extends from the most luminous quasars down to intermediate luminosities, supporting a downsizing picture for black hole accretion over cosmic time.
  • The systematic offset in black hole mass at fixed luminosity implies that the black hole mass function at z~6 peaks at lower masses than at z~1, with implications for the progenitors of today's most massive black holes.
  • If the Eddington-ratio-dependent calibration is correct, the super-Eddington fraction doubles, significantly alleviating the tension between the rapid emergence of billion-solar-mass black holes and the limited time available at z>6.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • If the SHELLQs sample is representative, then the intrinsic black hole mass function at z~6 is skewed toward masses below 10^9 M⊙, and the space density of lower-mass active black holes is higher than previously inferred from luminous quasar surveys alone.
  • The elevated Balmer decrements and red optical continua seen in a subset of objects (J0844−0132 and J1146−0005) suggest a possible connection to the 'Little Red Dot' population, implying an evolutionary sequence from dust-obscured rapid growth to unobscured quasar phases.
  • A clean test of the paper's central result would be a systematic reverberation mapping campaign of a few z~6 quasars using JWST to directly measure the BLR size and check the R_BLR–luminosity relation at high redshift.
  • The result that 22% are super-Eddington under the Woo+2026 calibration is sensitive to the assumed f-factor evolution; future ALMA or JWST observations of host galaxy dynamics could provide independent BH mass checks via the M-sigma relation.
Original abstract

We present near-infrared spectroscopy of 21 quasars at 6.07 < z < 6.90 obtained with JWST/NIRSpec and Subaru/MOIRCS. These targets have absolute ultraviolet magnitudes of -25 < M_1450 < -22 and are drawn from a sample of z>6 quasars identified in the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project. These quasars occupy the intermediate-luminosity regime between luminous quasars and the faint high-redshift AGNs uncovered by JWST. We detect broad Balmer emission lines and MgII 2798 with underlying continua from the NIRSpec and MOIRCS targets, respectively. The virial black hole masses of this sample span a wide range of 7.2 < log M_BH/M_sun < 9.4, with Eddington ratios of -1.3 < log L_bol/L_Edd < 0.4. Combining these measurements with our previous mass estimates for other SHELLQs quasars, we construct a sample of 27 quasars with M_BH estimates at 6 < z < 7 and derive the distributions of M_BH and L_bol/L_Edd. When compared with luminosity-matched quasars at z ~ 1.3, we find median offsets of delta log M_BH/M_sun = -0.4 and Delta log L_bol/L_Edd = 0.2 in the high-redshift sample. In addition, 11% of the high-redshift quasars are accreting near or above the Eddington limit. As a systematic check, adopting the Eddington-ratio-dependent calibration of single-epoch M_BH estimates increases the inferred super-Eddington fraction to 22%. These results indicate that a representative population of distant supermassive black holes undergo a rapid accretion phase, although not as extreme as that seen in the most luminous quasar population, consistent with the anti-hierarchical growth scenario of supermassive black holes.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. 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.

Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-09-23: 1 request, 8,072 input tokens.

What the abstract itself states, as probabilities: claims first 0.04 · states limitation 0.57 · human participants 0.02 · controlled comparison 0.87 · randomized assignment 0.01 · states quantitative result 0.99 · compares with prior results 0.96 · mentions code or data availability 0.02.

The abstract, sentence by sentence

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

We present near-infrared spectroscopy of 21 quasars at 6.07 < z < 6.90 obtained with JWST/NIRSpec and Subaru/MOIRCS. These targets have absolute ultraviolet magnitudes of -25 < M_1450 < -22 and are drawn from a sample of z>6 quasars identified in the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project. These quasars occupy the intermediate-luminosity regime between luminous quasars and the faint high-redshift AGNs uncovered by JWST. We detect broad Balmer emission lines and MgII 2798 with underlying continua from the NIRSpec and MOIRCS targets, respectively. The virial black hole masses of this sample span a wide range of 7.2 < log M_BH/M_sun < 9.4, with Eddington ratios of -1.3 < log L_bol/L_Edd < 0.4. Combining these measurements with our previous mass estimates for other SHELLQs quasars, we construct a sample of 27 quasars with M_BH estimates at 6 < z < 7 and derive the distributions of M_BH and L_bol/L_Edd. When compared with luminosity-matched quasars at z ~ 1.3, we find median offsets of delta log M_BH/M_sun = -0.4 and Delta log L_bol/L_Edd = 0.2 in the high-redshift sample. In addition, 11% of the high-redshift quasars are accreting near or above the Eddington limit. As a systematic check, adopting the Eddington-ratio-dependent calibration of single-epoch M_BH estimates increases the inferred super-Eddington fraction to 22%. These results indicate that a representative population of distant supermassive black holes undergo a rapid accretion phase, although not as extreme as that seen in the most luminous quasar population, consistent with the anti-hierarchical growth scenario of supermassive black holes.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 We present near-infrared spectroscopy of 21 quasars at 6.07 < z < 6.90 obtained with JWST/NIRSpec and Subaru/MOIRCS. method 0.70 0.97 0.02 asserted 1.00
s1 These targets have absolute ultraviolet magnitudes of -25 < M_1450 < -22 and are drawn from a sample of z>6 quasars identified in the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project. method 0.53 0.53 0.02 asserted 1.00
s2 These quasars occupy the intermediate-luminosity regime between luminous quasars and the faint high-redshift AGNs uncovered by JWST. background 0.92 0.19 0.03 asserted 1.00
s3 We detect broad Balmer emission lines and MgII 2798 with underlying continua from the NIRSpec and MOIRCS targets, respectively. result 0.84 0.96 0.02 asserted 1.00
s4 The virial black hole masses of this sample span a wide range of 7.2 < log M_BH/M_sun < 9.4, with Eddington ratios of -1.3 < log L_bol/L_Edd < 0.4. result 1.00 0.96 0.05 asserted 1.00
s5 Combining these measurements with our previous mass estimates for other SHELLQs quasars, we construct a sample of 27 quasars with M_BH estimates at 6 < z < 7 and derive the distributions of M_BH and L_bol/L_Edd. contribution 0.53 0.97 0.04 asserted 1.00
s6 When compared with luminosity-matched quasars at z ~ 1.3, we find median offsets of delta log M_BH/M_sun = -0.4 and Delta log L_bol/L_Edd = 0.2 in the high-redshift sample. result 1.00 0.96 0.10 asserted 1.00
s7 In addition, 11% of the high-redshift quasars are accreting near or above the Eddington limit. result 1.00 0.95 0.11 asserted 1.00
s8 As a systematic check, adopting the Eddington-ratio-dependent calibration of single-epoch M_BH estimates increases the inferred super-Eddington fraction to 22%. result 0.74 0.90 0.04 asserted 1.00
s9 These results indicate that a representative population of distant supermassive black holes undergo a rapid accretion phase, although not as extreme as that seen in the most luminous quasar population, consistent with the anti-hierarchical growth scenario of supermassive black holes. interpretation 1.00 0.61 0.91 hedged possibility 0.99

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

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
not run
  • 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

Figures
Figure 1. The redshift - M1450 distribution of the SHEL￾LQs quasars with available BH mass estimates (red). Those with Balmer-line-based MBH estimates available from JWST observations are shown as small circles, and those with Mg II-based MBH estimates from ground-based observations are shown as crosses. The SHELLQs quasars presented in this paper are highlighted with outer circles. The remain￾ing SHELLQs quasars, all with Mg II-based MBH estimates, are taken from O19, Y. Matsuoka et al. (2019a), and N. Kato et al. (2020). Luminous quasars targeted in the JWST EIGER program (blue; M. Yue et…
Figure 2. The NIRSpec G395M spectra of the JWST targets. Flux densities are presented in units of 10−20 erg cm−2 s −1 ˚A −1 . The observed wavelengths of Balmer lines and [O III] are indicated by vertical orange dashed lines. For J2236+0032 and J1512+4422, Hγ, Hδ, and Hϵ are seen in absorption. Weaker emission lines are also identified in the data, such as [O III] λ4364 for some objects
Figure 3. Spectral models for the first half of the JWST targets in the rest frame. Note the different y-axis scale from
Figure 5. UV (αλ,UV) and optical (αλ,optical) continuum slopes. The JWST targets in this work are shown as red circles with each object labeled by a letter as indicated in the lower right. The dust-obscured broad-line SHELLQs objects observed by Y. Matsuoka et al. (2025a) are shown as black crosses. The continuum slopes of typical 1 < z < 2 quasars measured by J. Selsing et al. (2016) are shown as an open triangle. The color window used for the selection of Little Red Dots in D. D. Kocevski et al. (2025) is indicated by the shaded region. The dashed line indicates the 1:1 relation
Figure 6. Comparison of the FWHMs of broad Balmer emission lines. Red solid lines show the line correlation where the slope is fixed to 1. Grey dashed lines show the one-to-one relation. In the Hα vs Hβ plot, the local relation of J. E. Greene & L. C. Ho (2005) and the relation at 0.5 < z < 3 from A. Schulze et al. (2018) are indicated by cyan and green dashed lines, respectively. 44 45 log10 L5100, QSO [erg s－1] 43 44 lo g10 L H α [e r g s －1] z=6 (total) z=6 (broad) LRD Local (total) Local (broad) 44 45 log10 L5100, QSO [erg s－1] 42 43 44 lo g10 L H β [e r g s －1] 44 45 log10 L5100, QSO…
Figure 7. Correlations between 5100 ˚A luminosity and Balmer line luminosities from Hα to Hδ. Here we use the host– galaxy–subtracted 5100 ˚A luminosity (L5100,QSO) based on JWST/NIRCam F356W imaging decomposition (X. Ding et al. 2025). In each panel, the luminosities of the broad-line components are shown as red circles, while those including both broad and narrow components are shown as open black diamonds. For each line pair, the best-fit linear relation is plotted as a solid line with the shaded area indicating the 1σ scatter of the residuals relative to the best-fit relation. The gray…
Figure 8. Balmer decrements, LHα/LHβ, as a function of the Hα luminosity. The symbols are the same as in
Figure 9. Hα/Hβ and Hγ/Hβ ratios. Red filled circles rep￾resent the broad emission lines, while black open diamonds show the total emission lines. Gray dashed lines connect the two measurements for each object. Each object is annotated as in
Figure 10. Balmer emission line fitting for J0217−0208. (Left:) Hβ+[O III] complex. The line colors are the same as in
Figure 11. The K-band spectra of the 9 MOIRCS targets (black). For visualization purposes, the spectrum in each panel is smoothed using a Gaussian kernel with σ = 2 pixels. The noise spectrum is shown in grey. The best-fit power-law continuum, iron, and Mg II emission line models are shown as blue, orange, and green dashed curves, respectively, and their sum is shown as solid red curves. The iron model in this figure is based on the I Zw 1 template by M. Vestergaard & B. J. Wilkes (2001). The vertical black dotted lines show the expected Mg II centers from their systemic redshifts. The…
Figure 13. Comparison of the Hβ-based and Hα-based MBH for the JWST targets. Each object is annotated as in
Figure 14. (Left) Black hole mass–bolometric luminosity distribution at z ∼ 6–7. SHELLQs quasars with JWST-based Hβ MBH measurements are shown as red diamonds, while those with Mg II-based MBH are shown as orange circles. Filled symbols indicate the SHELLQs quasars observed by MOIRCS in this work, whereas open symbols are taken from O19 and N. Kato et al. (2020). For the JWST targets in this work, the host-galaxy contribution to the 5100 ˚A luminosity has been subtracted based on the NIRCam decomposition analysis of X. Ding et al. (2025). Hβ-based MBH measurements for z > 6 luminous quasars…
Figure 15. Distribution of black hole mass (left) and Eddington ratio (right) of the 27 SHELLQs quasars at z ∼ 6–7 (orange) and the luminosity-matched SDSS DR16 quasars at z ≈ 1.3 (black). The low-redshift sample is extracted from Monte Carlo resampling to reproduce the Lbol distribution of the high-redshift sample. The black histogram shows the median probability distribution function (PDF) in each log MBH/M⊙ or log Lbol/LEdd bin over the Monte Carlo realizations, while the grey shaded area indicates the 16–84 percentile. The median log(MBH/M⊙) and log(Lbol/LEdd) values for the high-redshift…

Showing 13 of the paper's 16 figures. See all figures in the PDF ↗ Figures reproduced from arXiv:2609.09266 by the authors.

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