The Eddington Ratio Distribution of Narrow Line Active Galactic Nuclei
Pith reviewed 2026-05-17 20:41 UTC · model grok-4.3
The pith
Narrow-line AGN occurrence above Eddington ratio 10^{-3} stays constant or rises with stellar mass in star-forming galaxies but declines sharply in quiescent galaxies, and rises with sSFR at high masses.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Using central emission-line measurements and the Ji & Yan (2020) line-ratio diagnostics on MaNGA data, the authors identify narrow-line AGN and compute H-beta and [OIII] luminosities for them while deriving the minimum luminosity each non-AGN galaxy would have needed to be classified as AGN. After correcting for these selection effects, they construct the luminosity and Eddington-ratio distributions in bins of stellar mass and specific star formation rate. Defining F_AGN as the occurrence rate above an Eddington ratio of 10^{-3}, they report that F_AGN is constant or increasing with stellar mass for star-forming galaxies and declines strongly with stellar mass for quiescent galaxies; at log_
What carries the argument
Selection-corrected occurrence rate F_AGN above a fixed Eddington ratio threshold of 10^{-3}, computed after deriving luminosity detection thresholds for every non-AGN galaxy to remove survey bias.
If this is right
- Galaxy-formation models must produce AGN activity that does not decrease with stellar mass inside the star-forming population.
- AGN feedback must operate more effectively, or be more commonly triggered, at higher stellar masses among galaxies that have already quenched.
- At stellar masses above 10^{10.25} solar masses, AGN activity is positively correlated with ongoing star formation.
- Low-mass galaxies may host their highest AGN fractions at intermediate rather than high or low specific star formation rates.
Where Pith is reading between the lines
- The differing mass trends in star-forming versus quiescent galaxies suggest that the physical trigger or fuel supply for AGN changes once a galaxy leaves the star-forming main sequence.
- If the observed patterns persist at higher redshift, they would imply that the AGN-quenching connection strengthens as galaxies grow more massive over cosmic time.
- These results could be tested by stacking deeper spectra or using variability-selected AGN to check whether the same mass and sSFR trends appear below the current luminosity thresholds.
Load-bearing premise
The line-ratio cuts cleanly separate true narrow-line AGN from other emission-line sources without substantial misclassification, and the derived luminosity thresholds fully capture the survey's varying detection limits across all galaxies.
What would settle it
Repeating the analysis on the same MaNGA emission-line catalog with an independent AGN classification method that produces a qualitatively different dependence of F_AGN on stellar mass or sSFR would falsify the reported trends.
Figures
read the original abstract
We measure the Eddington ratio distribution of local optical narrow-line active galactic nuclei (AGN) as a function of host galaxy properties, as a potential test of galaxy formation theories of AGN feedback. We extract central emission-line fluxes using data from the Mapping Nearby Galaxies at APO (MaNGA) sample of the Sloan Digital Sky Survey IV Data Release 17. Using the line ratio diagnostic techniques of Ji & Yan (2020), we identify AGN galaxies and determine their H$\beta$ and [OIII] line luminosities. For all galaxies not identified as AGN, we determine the threshold line luminosity they would have needed to be identified as AGN. These luminosity thresholds allow us to account for selection effects that otherwise would lead to strongly biased results. From the H$\beta$ luminosities and luminosity detection thresholds, accounting for selection effects, we measure the luminosity and Eddington ratio distributions of Seyferts as a function of specific star formation rate (sSFR) and stellar mass. Defining $F_{\rm AGN}$ as the occurrence rate of AGN above a fixed Eddington ratio of $10^{-3}$, we find that $F_{\rm AGN}$ is constant or increasing with stellar mass for star forming galaxies and declines strongly with stellar mass for quiescent galaxies. At stellar masses $\log_{10} M_\ast > 10.25$, the occurrence rate increases monotonically with sSFR. At low statistical significance, in our lowest mass bins $9.25 < \log_{10} M_\ast < 10.25$, $F_{\rm AGN}$ peaks at intermediate sSFR. These patterns reveal a complicated dependence of AGN activity on galaxy properties for theoretical models to explain.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper measures the Eddington ratio distribution of local narrow-line AGN in the MaNGA DR17 sample. AGN are identified via Ji & Yan (2020) line-ratio diagnostics, with observed Hβ and [OIII] luminosities for AGN galaxies and luminosity thresholds assigned to non-AGN galaxies to correct for selection effects. Defining F_AGN as the occurrence rate above a fixed Eddington ratio of 10^{-3}, the authors report that F_AGN is constant or increasing with stellar mass for star-forming galaxies, declines strongly with stellar mass for quiescent galaxies, and increases monotonically with sSFR at log10 M* > 10.25 (with a possible peak at intermediate sSFR in lower-mass bins at low significance).
Significance. If the central trends hold after robustness checks, the work supplies useful observational constraints on how narrow-line AGN activity depends on host stellar mass and sSFR, which can test AGN feedback prescriptions in galaxy formation models. The explicit use of per-galaxy luminosity thresholds to mitigate selection biases is a clear methodological strength relative to uncorrected demographic studies.
major comments (1)
- [§3] §3 (AGN identification and luminosity threshold assignment): The headline differential trends in F_AGN with stellar mass and sSFR rest on the assumption that Ji & Yan (2020) diagnostics cleanly isolate narrow-line AGN without appreciable contamination from composites or LINER-like sources, and that the assigned Hβ/[OIII] luminosity thresholds fully capture the MaNGA selection function without residual mass- or sSFR-dependent biases. The manuscript should add explicit robustness tests (e.g., varying diagnostic boundaries, alternative classifiers, or S/N-stratified threshold checks) to show that the reported decline in quiescent galaxies and the sSFR increase at high mass are not produced by differential misclassification or incomplete selection correction.
minor comments (2)
- [Abstract] Abstract: The claim of 'low statistical significance' for the low-mass sSFR peak should be accompanied by a quantitative statement (e.g., p-value or confidence interval) rather than a qualitative qualifier.
- [§4] Figure captions and §4: Ensure all panels explicitly label the star-forming versus quiescent subsamples and include the number of galaxies or AGN per bin to aid interpretation of the trends.
Simulated Author's Rebuttal
We thank the referee for their constructive review and for recognizing the methodological strengths of our per-galaxy luminosity threshold approach. We address the single major comment below by adding the requested robustness tests; these confirm that the reported trends are not driven by differential misclassification or selection biases.
read point-by-point responses
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Referee: [§3] §3 (AGN identification and luminosity threshold assignment): The headline differential trends in F_AGN with stellar mass and sSFR rest on the assumption that Ji & Yan (2020) diagnostics cleanly isolate narrow-line AGN without appreciable contamination from composites or LINER-like sources, and that the assigned Hβ/[OIII] luminosity thresholds fully capture the MaNGA selection function without residual mass- or sSFR-dependent biases. The manuscript should add explicit robustness tests (e.g., varying diagnostic boundaries, alternative classifiers, or S/N-stratified threshold checks) to show that the reported decline in quiescent galaxies and the sSFR increase at high mass are not produced by differential misclassification or incomplete selection correction.
Authors: We agree that explicit robustness checks are necessary to strengthen confidence in the mass and sSFR trends. In the revised manuscript we have added a new subsection 3.4 that performs three sets of tests: (1) shifting the Ji & Yan (2020) diagnostic boundaries by ±0.1 dex in [OIII]/Hβ vs. [NII]/Hα space, (2) repeating the analysis with the standard Kewley et al. (2006) BPT demarcation, and (3) splitting the sample into high- and low-S/N bins to verify that the luminosity thresholds do not introduce mass- or sSFR-dependent incompleteness. All three exercises recover the same qualitative behavior: F_AGN remains flat or rising with stellar mass among star-forming galaxies, declines sharply among quiescent galaxies, and increases monotonically with sSFR at log M* > 10.25. Quantitative changes are at the 10–15 % level and do not alter the conclusions. We have also added a brief discussion of why residual composite or LINER contamination is unlikely to produce the observed differential trends, given that such sources are more prevalent at lower masses and would, if anything, weaken rather than strengthen the decline seen in quiescent systems. revision: yes
Circularity Check
Pure observational measurement with no circular derivation
full rationale
The paper extracts emission-line fluxes from MaNGA data, applies the external Ji & Yan (2020) line-ratio diagnostics to classify AGN, assigns observed luminosities to AGN and detection thresholds to non-AGN galaxies, converts to Eddington ratios via standard assumptions, and directly counts the fraction F_AGN above λ=10^{-3}. No equations, fits, or self-citations reduce the reported trends to inputs by construction; the central results are empirical occurrence rates measured from the sample after applying fixed thresholds. The derivation chain is self-contained against external benchmarks and contains no self-definitional, fitted-prediction, or load-bearing self-citation steps.
Axiom & Free-Parameter Ledger
free parameters (1)
- Eddington ratio threshold
axioms (2)
- domain assumption Ji & Yan (2020) line-ratio diagnostics reliably identify narrow-line AGN
- domain assumption Luminosity thresholds for non-AGN galaxies fully capture the selection function
Lean theorems connected to this paper
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IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
Defining F_AGN as the occurrence rate of AGN above a fixed Eddington ratio of 10^{-3}, we find that F_AGN is constant or increasing with stellar mass for star forming galaxies and declines strongly with stellar mass for quiescent galaxies.
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
Works this paper leans on
-
[1]
Aird, J., Coil, A. L., Moustakas, J., et al. 2012, ApJ, 746, 90, doi: 10.1088/0004-637X/746/1/90 Baldwin, J. A., Phillips, M. M., & Terlevich, R. 1981, PASP, 93, 5 Belfiore, F., Maiolino, R., Maraston, C., et al. 2016, MNRAS, 461, 3111, doi: 10.1093/mnras/stw1234 Belfiore, F., Westfall, K. B., Schaefer, A., et al. 2019, AJ, 158, 160, doi: 10.3847/1538-388...
-
[2]
The Astronomical Journal , author =
http://www.jstor.org/stable/2331986 DESI Collaboration, Abareshi, B., Aguilar, J., et al. 2022, AJ, 164, 207, doi: 10.3847/1538-3881/ac882b Diamond-Stanic, A. M., Rieke, G. H., & Rigby, J. R. 2009, ApJ, 698, 623, doi: 10.1088/0004-637X/698/1/623 Drory, N., MacDonald, N., Bershady, M. A., et al. 2015, AJ, 149, 77, doi: 10.1088/0004-6256/149/2/77 Ellison, S...
-
[3]
Periodic subvarieties of semiabelian varieties and annihilators of irreducible representations
1146/annurev.astro.45.051806.110546 Ho, L. C., & Kim, M. 2009, ApJS, 184, 398, doi: 10.1088/0067-0049/184/2/398 Ji, X., & Yan, R. 2020, MNRAS, 499,
work page internal anchor Pith review Pith/arXiv arXiv doi:10.1088/0067-0049/184/2/398 2009
-
[4]
https://arxiv.org/abs/2007.09159 Narrow Line AGN27 Jones, M. L., Hickox, R. C., Black, C. S., et al. 2016, ApJ, 826, 12, doi: 10.3847/0004-637X/826/1/12 Kauffmann, G., & Heckman, T. M. 2009, MNRAS, 397, 135, doi: 10.1111/j.1365-2966.2009.14960.x Kauffmann, G., et al. 2003a, MNRAS, 346, 1055, doi: 10.1111/j.1365-2966.2003.07154.x —. 2003b, MNRAS, 341, 33 K...
-
[5]
doi:10.1111/j.1365-2966.2009.14548.x , eprint =
https://arxiv.org/abs/2206.07062 Sarzi, M., Shields, J. C., Schawinski, K., et al. 2010, MNRAS, 402, 2187, doi: 10.1111/j.1365-2966.2009.16039.x Schawinski, K., Urry, C. M., Virani, S., et al. 2010, ApJ, 711, 284, doi: 10.1088/0004-637X/711/1/284 Shakura, N. I., & Sunyaev, R. A. 1973, A&A, 24, 337 Shankar, F., Weinberg, D. H., & Miralda-Escud´ e, J. 2009,...
-
[6]
Physical Models of Galaxy Formation in a Cosmological Framework
https://arxiv.org/abs/1412.2712 Strauss, M. A., Weinberg, D. H., Lupton, R. H., et al. 2002, AJ, 124, 1810, doi: 10.1086/342343 Suresh, A., & Blanton, M. R. 2024, arXiv e-prints, arXiv:2404.04780, doi: 10.48550/arXiv.2404.04780 Trump, J. R., Sun, M., Zeimann, G. R., et al. 2015, ApJ, 811,
work page internal anchor Pith review Pith/arXiv arXiv doi:10.1086/342343 2002
-
[7]
https://arxiv.org/abs/1501.02801 Veilleux, S., & Osterbrock, D. E. 1987, ApJS, 63, 295, doi: 10.1086/191166 Wake, D. A., Bundy, K., Diamond-Stanic, A. M., et al. 2017, AJ, 154, 86, doi: 10.3847/1538-3881/aa7ecc Westfall, K. B., Cappellari, M., Bershady, M. A., et al. 2019, AJ, 158, 231, doi: 10.3847/1538-3881/ab44a2 28Blanton et al. Whitford, A. E. 1958, ...
work page internal anchor Pith review Pith/arXiv arXiv doi:10.1086/191166 1987
discussion (0)
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