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arxiv: 2605.24884 · v1 · pith:DT5S4E6Znew · submitted 2026-05-24 · 🌌 astro-ph.CO

Preliminary cosmological results using extreme accretors Quasar formalism

Rodrigo Sandoval-Orozco , Castalia Alenka Negrete , Paola Marziani , Jackson Levi Said This is my paper

Pith reviewed 2026-06-30 00:00 UTC · model grok-4.3

classification 🌌 astro-ph.CO
keywords xA quasarsHubble constantdark energycosmologyactive galactic nucleidispersionSNIaCMB
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The pith

Standardized extreme accretor quasars give H0 = 69.8 ± 2.2 km s^{-1} Mpc^{-1} from the sample alone.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper compiles a cleaned sample of xA quasars and applies the formalism to constrain three cosmological models. It reports a Hubble constant of 69.8 ± 2.2 km s^{-1} Mpc^{-1} using only the quasar data and a tighter 69.0 ± 0.9 when adding supernovae, chronometers and CMB priors. A weak preference for dynamical dark energy is found over the standard LambdaCDM model. The authors emphasize that intrinsic dispersion remains the key barrier to using AGN samples as precise cosmological tools.

Core claim

Using a completely cleaned and standardized sample of xA quasars compiled from literature, the xA formalism is applied to test LambdaCDM, wCDM and w0waCDM models. This results in H0 = 69.8 ± 2.2 km s^{-1} Mpc^{-1} for the quasar sample alone and H0 = 69.0 ± 0.9 km s^{-1} Mpc^{-1} in combination with SNIa, cosmic chronometers and CMB distance priors. Both wCDM and w0waCDM show a weak Bayesian preference over LambdaCDM. The analysis compares this to other AGN methods such as reverberation mapping and X-ray UV relations, concluding that intrinsic dispersion is the main unresolved issue across all such approaches.

What carries the argument

The xA Quasar formalism, which standardizes extreme accretor quasars as cosmological probes by reducing scatter in their distance indicators.

Load-bearing premise

The xA quasar sample can be cleaned and standardized enough that its remaining intrinsic dispersion does not limit the cosmological constraints.

What would settle it

Finding that the dispersion in the standardized xA sample prevents H0 constraints tighter than current values would show the method cannot yet compete as a robust probe.

Figures

Figures reproduced from arXiv: 2605.24884 by Castalia Alenka Negrete, Jackson Levi Said, Paola Marziani, Rodrigo Sandoval-Orozco.

Figure 1
Figure 1. Figure 1: Distance modulus measured with the complete sample with the x-axis as redshift. Different colors represent [PITH_FULL_IMAGE:figures/full_fig_p006_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Parameter space of H0 and Ωm,0 for the ΛCDM model tested for with xA Qso sample showing the results using CMB light, the Pantheon+ SNIa, the Cosmic Chronometers analysis and the Angular Quasar sample. Those are the samples that are capable of constraining the cosmological parameters individually. expectation (w0 = −1, wa = 0), the large uncertainties prevent any decisive conclusion. This trend, where the d… view at source ↗
Figure 3
Figure 3. Figure 3: Bi-dimensional contour plots for the wCDM model in the Ωm,0 − w0 plane at 1 and 2σ confidence levels obtained for each dataset combination marked in the label. The marked dashed line represents where w0 = 1 or the ΛCDM confirmation. Our comparative analysis of Quasar cosmological probes yields several key insights. A primary finding is that the xA Quasar sample is the only approach capable of constraining … view at source ↗
Figure 4
Figure 4. Figure 4: Bi-dimensional contour plots for the w0waCDM model tested in the w0 − wa plane at 1 and 2σ confidence levels obtained from each dataset combination marked in the label. The marked dashed lines represents w0 = 1 and wa = 0 or the ΛCDM confirmation. (ln Bij = −1.80). This, depict the large error margin for the free parameter wa = −1.35+0.73 −0.80. Again, similar to the other Quasar analysis, this could be a … view at source ↗
Figure 5
Figure 5. Figure 5: Whisker plot for the different H0 estimations in the literature. Blue color represents measurements that depend on Cepheids distance ladder, red color the ones that depend on the early universe, and green ones the late-time determinations not dependent on distance ladder assumptions. We considered the measurements Planck 2018 (Aghanim et al., 2020), CMB distance priors (Chen et al., 2019), Atacama Cosmolog… view at source ↗
read the original abstract

We revisited the xA Quasar formalism from the cosmological point of view, where a completely cleaned and standardized sample is compiled from different literature references. This allowed us to test three different cosmological models including $w$CDM and $w_0w_a$CDM and $\Lambda$CDM resulting in a Hubble constant estimation of $H_0 = 69.8 \pm 2.2$~$\mathrm{km\,s^{-1}\,Mpc^{-1}}$ for the compiled sample alone and $H_0=69.0 \pm 0.9$~$\mathrm{km\,s^{-1}\,Mpc^{-1}}$ when combined with Type I Supernovae (SNIa), Cosmic Chronometers and the Cosmic Microwave Background (CMB) distance priors. Using both the $w$CDM and $w_0w_a$CDM a weak Bayesian preference for the dynamical dark energy models over the $\Lambda$CDM model was found. A comparative analysis was performed with other AGN based methods in cosmology like the Reverberation Mapping, the X-Ray and UV non-linear relation and the Angular distance measurements. We conclude that the significant intrinsic dispersion is a key issue present in all samples. Overcoming this dispersion is key to establish xA and other AGN samples as robust and precise cosmological probes.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

3 major / 0 minor

Summary. The manuscript compiles a cleaned and standardized sample of extreme accretor (xA) quasars from the literature and applies the xA formalism to constrain cosmology. It reports H0 = 69.8 ± 2.2 km s^{-1} Mpc^{-1} from the quasar sample alone and H0 = 69.0 ± 0.9 km s^{-1} Mpc^{-1} when combined with SNIa, cosmic chronometers, and CMB distance priors. The analysis tests ΛCDM, wCDM, and w0waCDM, finding a weak Bayesian preference for dynamical dark energy models, compares results to other AGN methods, and concludes that significant intrinsic dispersion remains the key unresolved issue across all AGN samples.

Significance. If the xA quasar standardization can be shown to be independent of the cosmological fit and if the intrinsic dispersion can be demonstrated not to dominate the error budget, the work would add a high-redshift AGN-based distance indicator to the set of cosmological probes. The reported H0 values are broadly consistent with Planck but the weak model preference and the paper's own emphasis on dispersion as the central limitation suggest that the current constraints do not yet reach the precision required to resolve the Hubble tension or to provide decisive model discrimination.

major comments (3)
  1. [Abstract] Abstract and concluding paragraph: The central claim that a 'completely cleaned and standardized sample' yields reliable H0 values and a Bayesian preference for dynamical dark energy is directly undermined by the explicit statement that 'significant intrinsic dispersion is a key issue present in all samples' and that 'Overcoming this dispersion is key to establish xA and other AGN samples as robust and precise cosmological probes.' This admission indicates that the quoted uncertainties (e.g., ±2.2 and ±0.9) may not fully capture the dominant scatter, rendering the numerical results and model odds difficult to interpret as robust constraints.
  2. [Abstract] Abstract: The fitting procedure and whether the xA standardization parameters (e.g., any luminosity or accretion-rate corrections) were derived independently of the cosmological likelihood is not specified. Without this information it is impossible to assess potential circularity when the quasar sample is later combined with SNIa and CMB priors whose calibrations may share underlying assumptions.
  3. [Abstract] Abstract: The reported weak Bayesian preference for wCDM and w0waCDM over ΛCDM rests on the same sample whose intrinsic dispersion is flagged as the dominant limitation. No quantitative assessment is provided of how the dispersion propagates into the evidence ratios or whether the preference survives when the scatter is treated as an additional systematic.

Simulated Author's Rebuttal

3 responses · 1 unresolved

We thank the referee for the careful reading of the manuscript and the constructive comments. We respond to each major comment below.

read point-by-point responses

  1. Referee: [Abstract] Abstract and concluding paragraph: The central claim that a 'completely cleaned and standardized sample' yields reliable H0 values and a Bayesian preference for dynamical dark energy is directly undermined by the explicit statement that 'significant intrinsic dispersion is a key issue present in all samples' and that 'Overcoming this dispersion is key to establish xA and other AGN samples as robust and precise cosmological probes.' This admission indicates that the quoted uncertainties (e.g., ±2.2 and ±0.9) may not fully capture the dominant scatter, rendering the numerical results and model odds difficult to interpret as robust constraints.

    Authors: We agree that the abstract and conclusion should be revised for better balance. The quoted uncertainties are the statistical errors obtained from the likelihood analysis of the compiled sample. The conclusion already identifies intrinsic dispersion as the dominant remaining limitation across AGN samples, including ours. We will revise the abstract and concluding paragraph to state more explicitly that the results are subject to this dispersion, which affects the precision and robustness of the constraints, while retaining the reported central values and errors. revision: yes

  2. Referee: [Abstract] Abstract: The fitting procedure and whether the xA standardization parameters (e.g., any luminosity or accretion-rate corrections) were derived independently of the cosmological likelihood is not specified. Without this information it is impossible to assess potential circularity when the quasar sample is later combined with SNIa and CMB priors whose calibrations may share underlying assumptions.

    Authors: The xA standardization parameters, including luminosity and accretion-rate corrections, are taken directly from the established xA formalism in the prior literature and are held fixed when fitting the cosmological models to the compiled sample. No re-derivation or optimization of these parameters occurs within the cosmological likelihood. We will add a clarifying statement in the methods section to make this independence explicit. revision: yes

  3. Referee: [Abstract] Abstract: The reported weak Bayesian preference for wCDM and w0waCDM over ΛCDM rests on the same sample whose intrinsic dispersion is flagged as the dominant limitation. No quantitative assessment is provided of how the dispersion propagates into the evidence ratios or whether the preference survives when the scatter is treated as an additional systematic.

    Authors: The Bayesian evidence ratios were computed using the reported measurement uncertainties. The manuscript already describes the preference as weak. A quantitative assessment of the effect of modeling the intrinsic dispersion as an extra systematic on the evidence ratios is not included, as this would require a more elaborate hierarchical error model. revision: partial

standing simulated objections not resolved
  • Quantitative assessment of how intrinsic dispersion propagates into the Bayesian evidence ratios

Circularity Check

0 steps flagged

No circularity: derivation uses external standardization and independent cosmological fits

full rationale

The paper compiles an xA quasar sample from literature references, applies the existing xA formalism for standardization, and performs cosmological fits to obtain H0 values both from the sample alone and in combination with external datasets (SNIa, cosmic chronometers, CMB priors). No equations or steps in the abstract or described content reduce the reported H0 or model preferences to the inputs by construction, self-definition, or self-citation chains. The standardization parameters and cosmological constraints are treated as separable, with the intrinsic dispersion explicitly flagged as an unresolved external limitation rather than hidden in the fit. This satisfies the criteria for a self-contained derivation against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the domain assumption that the xA quasar properties can be standardized across literature sources to serve as cosmological distance indicators; no free parameters or invented entities are explicitly introduced in the abstract, but the cosmological models themselves contain the usual dark-energy equation-of-state parameters.

axioms (1)
  • domain assumption The xA quasar sample can be cleaned and standardized sufficiently for cosmological use despite acknowledged intrinsic dispersion
    Stated implicitly by the decision to compile and apply the sample to cosmological models; the abstract itself identifies dispersion as the key remaining issue.

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discussion (0)

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Reference graph

Works this paper leans on

5 extracted references · 4 canonical work pages · 2 internal anchors

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