A Sizable Discrepancy in Ground-Based JAGB Distances to Nearby Galaxies

Gagandeep S. Anand

REVIEW 4 major objections 4 minor 1 cited by

A Sizable Discrepancy in Ground-Based JAGB Distances to Nearby Galaxies

T0 review · 4 major / 4 minor · reviewed 2026-08-08 · deepseek-v4-flash

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Pith's one-line read The paper reports that ground-based JAGB distances to thirteen nearby galaxies are, on average, 0.17 magnitudes (about 9%) shorter than HST optical TRGB distances, and argues that the HST color-magnitude diagrams locate the problem in the…

desk verdict A credible and important discrepancy between ground-based JAGB and HST TRGB distances, but the paper overstates its case by blaming JAGB without an independent absolute calibration of the TRGB scale. read the letter →

arxiv 2502.07882 v2 pith:6QA6ZNKS submitted 2025-02-11 astro-ph.CO astro-ph.GA

Gagandeep S. Anand This is my paper · ORCID

classification astro-ph.COastro-ph.GA

keywords CarbonstarsDistanceindicatorsRedgianttipStellarJAGBTRGBladdercrowding

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

The paper challenges a recent claim that the JAGB and TRGB distance indicators agree to 1% in nearby galaxies. Comparing the same ground-based JAGB distances to uniformly processed HST optical TRGB distances for thirteen galaxies, it finds a mean offset of 0.17 magnitudes, or about 9% in distance, in the sense that the TRGB distances are farther. The paper argues, from inspection of the HST color-magnitude diagrams and from checks against independent TRGB measurements, that the JAGB distances are the ones that are too short, most plausibly because of stellar crowding or calibration problems in the ground-based near-infrared photometry. This matters because JAGB is proposed as a precise second-rung distance indicator for measuring the local Hubble constant, and a distance-scale bias of this size would need to be understood and corrected before JAGB distances can anchor that measurement.

What carries the argument

The argument is carried by a galaxy-by-galaxy comparison of two distance moduli: the JAGB modulus, derived from ground-based near-infrared photometry of carbon-rich asymptotic giant branch stars in the J region of the color-magnitude diagram, and the TRGB modulus, derived from space-based optical photometry of the tip of the red giant branch. The decisive diagnostic is the color-magnitude diagram itself: for each HST CMD the paper overplots the magnitude at which the TRGB would lie if the JAGB distance were correct, so that the eye can judge whether that implied tip matches the visible end of the red giant branch. A re-assembled error budget covering tip uncertainty, JAGB mode, smoothing scale, foreground reddening, and calibration zero points determines whether the mean difference is statistically meaningful, while checks against alternative TRGB measurements test whether the offset is an artifact of one catalog's photometry.

What would settle it

Measure JAGB (and, ideally, Cepheid and TRGB) distances for the same galaxies using the high-resolution near-infrared HST data now being collected: if space-based JAGB moduli shift to match the HST TRGB values, the ground-based photometry is the problem, whereas if the short JAGB moduli persist in space-based data, the bias is intrinsic to the JAGB method for this sample.

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Extended reading notes

Core claim

The paper's central claim is that the widely cited 1% agreement between the JAGB and TRGB distance scales breaks down when the same ground-based JAGB distance moduli are compared with uniformly reduced HST optical TRGB distances. For thirteen galaxies between 0.5 and 4 Mpc the mean offset is $\Delta\mu = 0.17 \pm 0.04$ (stat) $\pm 0.06$ (sys) mag, in the sense that the HST TRGB distances are farther by about 9% in distance. The author shows that the TRGB zero point is not the source of the offset, that independent HST TRGB measurements for subsamples reproduce it, and that in 9 of 13 HST color-magnitude diagrams the TRGB magnitude implied by the JAGB distance is inconsistent with the observed termination of the red giant branch. The paper therefore concludes that the ground-based JAGB distances are systematically too short, with stellar crowding and photometric calibration of the ground-based near-infrared data as the most plausible culprits.

Load-bearing premise

The interpretation that JAGB is at fault assumes the HST optical TRGB distances for the thirteen galaxies are accurate and unbiased, including their zero-point calibration and tip detection; if those TRGB distances were systematically too large, the same offset would appear even if the JAGB distances were correct.

Editorial extensions

If this is right

If the offset is real, ground-based JAGB distances in the 0.5-4 Mpc range are systematically short by roughly 9% and should not be combined with HST TRGB distances without a correction.
The same-direction offset found between HST optical TRGB and the ground-based near-infrared TRGB distances implies the problem is not unique to JAGB and may reflect crowding or calibration in the ground-based near-infrared data.
The agreement between JWST JAGB and other second-rung indicators at 7-23 Mpc need not be affected, because JWST's higher resolution avoids the crowding that afflicts ground-based imaging of these nearer galaxies.
The ongoing HST program that measures Cepheid, JAGB, and TRGB distances simultaneously in four of the galaxies can distinguish a ground-based systematic from an intrinsic property of the JAGB method.

Reading between the lines

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

If crowding is confirmed as the cause, ground-based JAGB magnitudes for the same stars should be systematically too bright relative to space-based magnitudes, because unresolved stars add light; this is directly checkable in the new HST images.
The earlier 1% agreement may have been reached because the TRGB and JAGB distances being compared came from the same ground-based near-infrared images, so both scales could share the same crowding or calibration bias while still agreeing with each other.
A practical consequence of the paper's interpretation is that JAGB needs a crowding calibration as a function of stellar density and distance, rather than only a zero-point calibration, before it can serve as a precise rung on the distance ladder.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

The headline is real: Anand finds a 0.17 mag offset between Lee et al.'s ground-based JAGB distances and EDD HST optical TRGB distances for 13 nearby galaxies, with the HST distances further. The number is a simple difference of published distance moduli with quoted statistical and systematic errors, and it is robust enough to matter. This should be read as a useful negative result for the JAGB scale and a direct challenge to the Freedman et al. 1% agreement claim. That alone makes the paper worth engaging with.

What is new is the comparison itself. No one had put these two public datasets side by side in this way, and the resulting offset contradicts a recent, high-profile claim. The paper also checks against ANGST and GHOSTS TRGB measurements and finds similar or larger offsets, which strengthens the case that the discrepancy is not an artifact of the EDD pipeline specifically. The author is a coauthor of the EDD catalog, but the JAGB values are independent, so this is not a circular comparison.

The soft spot is attribution. The visual CMD argument in Figure 1 is not an independent test: the JAGB-implied tip is just the EDD tip shifted by the same 0.17 mag, so it cannot tell you which scale is wrong. The ANGST and GHOSTS checks re-reduce the same HST data with similar TRGB methodology; they validate internal consistency across pipelines, not the absolute zero point. The agreement between EDD's -4.04 and CCHP's -4.05 shares the Rizzi et al. framework, so it does not exclude a systematic offset at the 0.15-0.20 mag level for these low-mass galaxies. The additional NIR TRGB offset of 0.12 mag is suggestive but degenerate: it could be ground-based calibration or crowding, but it could also mean the HST scale is biased high. Without an independent rung—Cepheids, Miras, or a geometric distance—for at least some of these galaxies, the strong conclusion that JAGB is at fault is not uniquely established.

The paper is short and clearly written. It would be stronger if it tabulated the individual values it used and explicitly compared with the CCHP TRGB distances used in the original 1% claim; the omission of that direct comparison is a missed opportunity. The discrepancy itself, however, is credible, and the distance-scale/H0 community needs to know about it. I would send this to a serious referee rather than desk reject; the analysis is methodologically simple, but the consequence is real and the resolution matters for the local Hubble constant program.

Referee Report

4 major / 4 minor

Summary. This manuscript compares ground-based near-infrared JAGB distance moduli from Lee et al. (2024c) (plus WLM and M33 from the same program) with space-based optical TRGB distance moduli from the Extragalactic Distance Database for thirteen galaxies at 0.5-4 Mpc. The central empirical finding is a mean offset of Δμ = 0.17 ± 0.04 (stat) ± 0.06 (sys) mag, with the HST TRGB distances farther; a smaller comparison with Zgirski et al. (2021) IRSF JAGB distances gives Δμ = 0.23 ± 0.05 (stat) ± 0.06 (sys) mag. The paper uses CMD inspection and comparisons with ANGST and GHOSTS TRGB distances to argue that the discrepancy is likely due to the ground-based JAGB photometry, plausibly crowding or calibration, and notes an ongoing HST program for simultaneous Cepheid/JAGB/TRGB measurements.

Significance. If the offset is real, it undercuts the claimed ~1% agreement between ground-based JAGB and TRGB in the nearby regime and is relevant to the choice of JAGB as a second-rung distance indicator for H0. The comparison is transparent: it uses only public catalogs, no parameters are fitted, and the error budget separates statistical and systematic contributions. However, the attribution to JAGB rather than TRGB is not independently established; ANGST and GHOSTS re-reduce the same HST imaging with similar TRGB methodology, so they do not supply an absolute calibration. The reported offset is therefore best viewed as a well-quantified discrepancy between two distance scales, with the cause still to be determined.

major comments (4)

[Abstract and §3] The claim that inspection of the CMDs makes a 'compelling case' that the issue lies in the underlying JAGB distances is not supported by the evidence presented. The ANGST and GHOSTS distances compared in §3 use the same HST imaging and similar TRGB analysis methods, and both ultimately share the Rizzi et al. (2007) zero-point framework; they therefore do not constitute an independent validation of the HST TRGB scale. To support the attribution, the paper would need an independent distance indicator for these galaxies (e.g., Cepheids, Miras, or geometric distances) or a direct space-based JAGB measurement from the same photometry.
[Figure 1] The bottom panels of Figure 1 are not an independent test of which distance scale is wrong. The 'JAGB-implied TRGB' magnitude is obtained by applying the measured Δμ = 0.17 mag shift to the EDD TRGB measurement, so the visual mismatch between the red line and the tip is a restatement of the offset, not new evidence. The same figure would look identical if the HST TRGB distances were systematically too large.
[§3, first paragraph] The zero-point check does not rule out a TRGB-side explanation. The agreement of EDD's average MF814W = -4.04 mag with CCHP's -4.05 mag is between two calibrations rooted in the same Rizzi et al. (2007) framework, and the comparison does not address whether that framework is biased at the ~0.15-0.20 mag level for the low-mass galaxies in this sample. Consequently, the statement that 'it seems unlikely that the TRGB zeropoint is responsible' is stronger than the evidence allows.
[§3, NIR-TRGB paragraph] The ground-based NIR TRGB comparison (Δμ = 0.12 ± 0.04 ± 0.07 mag in the same direction) is presented as evidence for a photometric calibration problem in the ground-based data, but this interpretation is degenerate with an HST TRGB scale that is biased high by a similar amount. The paper should state this degeneracy explicitly; as written, the paragraph moves from a measured offset to a preferred cause without ruling out the alternative.

minor comments (4)

[Figure 1 caption] There is a typo in the caption ('T op' should be 'Top'), and the four bottom CMD panels are not identified by galaxy name in the text, making it hard for the reader to map the examples to the sample.
[Abstract] The phrase 'the HST TRGB distances being further' should read 'farther'; the same wording appears in the abstract and in §2.
[References] Rizzi et al. (2007a) and (2007b) are the same ApJ paper (661, 815); the reference list has two entries with identical bibliographic data, which is confusing. The text should either cite it once or clearly distinguish the calibration and zero-point uses.
[§3] The section title 'Potential Solutions' overstates what the section does; the manuscript identifies possible causes but does not test them. A title such as 'Potential Explanations' would be more accurate.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the discrepancy is an external comparison of two independently published distance catalogs, with no fitted parameter or derived quantity reducing by construction to an input.

full rationale

This paper performs an observational comparison between ground-based JAGB distance moduli from Lee et al. (2024c) and space-based HST optical TRGB distance moduli from the EDD CMDs/TRGB catalog. The offset Δμ = 0.17 mag is computed directly from two external, publicly available catalogs; no parameter is fitted in this paper, and no equation defines the JAGB or TRGB distances in terms of each other. The visual CMD inspection plots the JAGB-implied RGB tip against the observed stellar distribution; while this cannot by itself distinguish a JAGB fault from a TRGB zero-point fault, it is a consistency check rather than a formal reduction of the conclusion to the input. The independent ANGST and GHOSTS TRGB measurements provide external (if methodologically similar) cross-checks, and the author's co-authorship of the EDD catalog is a self-citation but is not load-bearing because the JAGB values come from a different group and the comparison is reproducible from public data. The paper explicitly discusses the TRGB zero-point agreement and the possibility of HST systematics, acknowledging the degeneracy. No circular step of any enumerated kind is present.

Assumptions & free parameters 0 free parameters · 4 assumptions · 0 invented entities

The paper introduces no free parameters or new entities; its central claim is a comparison of published distances. The assumptions listed are the external calibration and data-quality premises the comparison depends on.

assumptions (4)

domain assumption The EDD HST TRGB distances for the 13 galaxies are accurate and unbiased.
The conclusion that JAGB is at fault requires the TRGB distances to be the correct reference. The paper argues this in Section 3 but does not provide an absolute calibration check.
domain assumption The Rizzi et al. (2007b) TRGB zero point (M_F814W = -4.04) applies uniformly across the sample.
Section 3 uses agreement with the CCHP value to rule out a zero point problem, assuming no per-galaxy zero point variations in the EDD catalog.
domain assumption The ground-based JAGB photometry and distances from Lee et al. (2024c) are taken at face value.
The paper re-tabulates uncertainties but does not re-reduce the photometry; the whole discrepancy analysis relies on the published JAGB catalog.
domain assumption A 15% uncertainty in foreground reddening is an adequate error model.
This uncertainty is folded into both JAGB and TRGB distance errors in Section 2 without testing the reddening model itself.

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Cite this review

Pith. "Pith review of A Sizable Discrepancy in Ground-Based JAGB Distances to Nearby Galaxies." pith.science (2026). https://pith.science/paper/6QA6ZNKS

@misc{pith2026250207882,
  author       = {Pith},
  title        = {Pith review of: A Sizable Discrepancy in Ground-Based JAGB Distances to Nearby Galaxies},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/6QA6ZNKS}},
  note         = {Machine review of arXiv:2502.07882}
}

abstract

Recently, Freedman et al. (2024) report agreement of distances derived from the Tip of the Red Giant Branch (TRGB) and the J-Region Asymptotic Giant Branch (JAGB) at the 1$\%$ level for both nearby galaxies with ground-based imaging (0.5-4 Mpc) as well distant galaxies with JWST imaging (7-23 Mpc). Here we compare the same ground-based JAGB distances to uniformly reduced space-based optical TRGB distances from the Hubble Space Telescope (HST). We uncover a significant offset between these two distance scales of $\Delta\mu$ = 0.17 $\pm$ 0.04 (stat) $\pm$ 0.06 (sys) mag (9$\%$ in distance), with the HST TRGB distances being further. Inspections of the HST color-magnitude diagrams make a compelling case that the issue lies in the underlying JAGB distances. The source of the disagreement may lie with the lower resolution or photometric calibration of the ground-based near-infrared data, a contrast to the general agreement found between JWST JAGB and other space-based, second-rung distance indicators (Cepheids, Miras, TRGB) presented within Riess et al. (2024). High-resolution, near-infrared observations from an ongoing HST program will enable the simultaneous measurement of Cepheid, JAGB, and TRGB distances in four of these nearby galaxies and allow us to investigate whether the discrepancy noted here is due to ground-based observational systematics, or something intrinsic to the JAGB method relevant for this particular sample. A resolution of this discrepancy is required if the JAGB is to be used to determine a highly precise local value of the Hubble constant.

Figures

Figures reproduced from arXiv: 2502.07882 by the authors.

**Figure 1.** Top: Comparison of ground-based JAGB (Lee et al. 2024c) and HST optical TRGB distance moduli (Jacobs et al. 2009; Anand et al. 2021) shown in red. We find a significant offset of ∆µ = 0.17 ± 0.04 (stat) ± 0.06 (sys) mag between the two samples. The blue points show the same comparison with JAGB distance moduli from Zgirski et al. (2021), but with only six overlapping targets. A postage stamp of a JAGB star in the ou… view at source ↗

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Reference graph

Works this paper leans on

23 extracted references · 2 canonical work pages · cited by 1 Pith paper

[1]

S., Rizzi, L., Tully, R

Anand, G. S., Rizzi, L., Tully, R. B., et al. 2021, AJ, 162, 80, doi: 10.3847/1538-3881/ac0440

doi:10.3847/1538-3881/ac0440 2021
[2]

L., Bono, G., Braga, V

Beaton, R. L., Bono, G., Braga, V. F., et al. 2018, SSRv, 214, 113, doi: 10.1007/s11214-018-0542-1

doi:10.1007/s11214-018-0542-1 2018
[3]

S., et al

Breuval, L., Riess, A., Anand, G. S., et al. 2023, A 1% cross-calibration of Cepheids, TRGB, and JAGB in five nearby galaxies with HST, HST Proposal. Cycle 31, ID. #17520

work page 2023
[4]

J., Williams, B

Dalcanton, J. J., Williams, B. F., Seth, A. C., et al. 2009, ApJS, 183, 67, doi: 10.1088/0067-0049/183/1/67

doi:10.1088/0067-0049/183/1/67 2009
[5]

Freedman, W. L. 2021, ApJ, 919, 16, doi: 10.3847/1538-4357/ac0e95

doi:10.3847/1538-4357/ac0e95 2021
[6]

L., & Madore, B

Freedman, W. L., & Madore, B. F. 2020, ApJ, 899, 67, doi: 10.3847/1538-4357/aba9d8

doi:10.3847/1538-4357/aba9d8 2020
[7]

L., Madore, B

Freedman, W. L., Madore, B. F., Jang, I. S., et al. 2024, arXiv e-prints, arXiv:2408.06153, doi: 10.48550/arXiv.2408.06153

arXiv doi:10.48550/arxiv.2408.06153 2024
[8]

A., Rizzi, L., Tully, R

Jacobs, B. A., Rizzi, L., Tully, R. B., et al. 2009, AJ, 138, 332, doi: 10.1088/0004-6256/138/2/332

doi:10.1088/0004-6256/138/2/332 2009

Show all 23 references

[9]

Lee, A. J. 2023, ApJ, 956, 15, doi: 10.3847/1538-4357/acee69

2023 doi
[10]

Owens, K. A. 2024a, ApJ, 961, 132, doi: 10.3847/1538-4357/ad12c7

doi
[11]

J., Freedman, W

Lee, A. J., Freedman, W. L., Madore, B. F., et al. 2024b, arXiv e-prints, arXiv:2408.03474, doi: 10.48550/arXiv.2408.03474 —. 2021, ApJ, 907, 112, doi: 10.3847/1538-4357/abd253

2021 doi arXiv
[12]

J., Rousseau-Nepton, L., Freedman, W

Lee, A. J., Rousseau-Nepton, L., Freedman, W. L., et al. 2022, ApJ, 933, 201, doi: 10.3847/1538-4357/ac7321

2022 doi
[13]

J., Monson, A

Lee, A. J., Monson, A. J., Freedman, W. L., et al. 2024c, ApJ, 967, 22, doi: 10.3847/1538-4357/ad32c7

doi
[14]

G., Freedman, W

Lee, M. G., Freedman, W. L., & Madore, B. F. 1993, ApJ, 417, 553, doi: 10.1086/173334

1993 doi
[15]

G., Casertano, S., et al

Li, S., Riess, A. G., Casertano, S., et al. 2024, ApJ, 966, 20, doi: 10.3847/1538-4357/ad2f2b

2024 doi
[16]

F., & Freedman, W

Madore, B. F., & Freedman, W. L. 1995, AJ, 109, 1645, doi: 10.1086/117391 —. 2020, ApJ, 899, 66, doi: 10.3847/1538-4357/aba045

1995 doi
[17]

J., de Jong, R

Radburn-Smith, D. J., de Jong, R. S., Seth, A. C., et al. 2011, ApJS, 195, 18, doi: 10.1088/0067-0049/195/2/18

2011 doi
[18]

G., Yuan, W., Macri, L

Riess, A. G., Yuan, W., Macri, L. M., et al. 2022, ApJL, 934, L7, doi: 10.3847/2041-8213/ac5c5b

2022 doi
[19]

G., Scolnic, D., Anand, G

Riess, A. G., Scolnic, D., Anand, G. S., et al. 2024, arXiv e-prints, arXiv:2408.11770, doi: 10.48550/arXiv.2408.11770

2024 doi arXiv
[20]

B., Makarov, D., et al

Rizzi, L., Tully, R. B., Makarov, D., et al. 2007a, ApJ, 661, 815, doi: 10.1086/516566 —. 2007b, ApJ, 661, 815, doi: 10.1086/516566

doi
[21]

B., Rizzi, L., Shaya, E

Tully, R. B., Rizzi, L., Shaya, E. J., et al. 2009, AJ, 138, 323, doi: 10.1088/0004-6256/138/2/323

2009 doi
[22]

D., & Nikolaev, S

Weinberg, M. D., & Nikolaev, S. 2001, ApJ, 548, 712, doi: 10.1086/319001

2001 doi
[23]

2021, ApJ, 916, 19, doi: 10.3847/1538-4357/ac04b2

Zgirski, B., Pietrzy´ nski, G., Gieren, W., et al. 2021, ApJ, 916, 19, doi: 10.3847/1538-4357/ac04b2

2021 doi

Pith tools

Reviewed August 8, 2026 · model on record in the stance chip above.

[1] [1]

S., Rizzi, L., Tully, R

Anand, G. S., Rizzi, L., Tully, R. B., et al. 2021, AJ, 162, 80, doi: 10.3847/1538-3881/ac0440

doi:10.3847/1538-3881/ac0440 2021

[2] [2]

L., Bono, G., Braga, V

Beaton, R. L., Bono, G., Braga, V. F., et al. 2018, SSRv, 214, 113, doi: 10.1007/s11214-018-0542-1

doi:10.1007/s11214-018-0542-1 2018

[3] [3]

S., et al

Breuval, L., Riess, A., Anand, G. S., et al. 2023, A 1% cross-calibration of Cepheids, TRGB, and JAGB in five nearby galaxies with HST, HST Proposal. Cycle 31, ID. #17520

work page 2023

[4] [4]

J., Williams, B

Dalcanton, J. J., Williams, B. F., Seth, A. C., et al. 2009, ApJS, 183, 67, doi: 10.1088/0067-0049/183/1/67

doi:10.1088/0067-0049/183/1/67 2009

[5] [5]

Freedman, W. L. 2021, ApJ, 919, 16, doi: 10.3847/1538-4357/ac0e95

doi:10.3847/1538-4357/ac0e95 2021

[6] [6]

L., & Madore, B

Freedman, W. L., & Madore, B. F. 2020, ApJ, 899, 67, doi: 10.3847/1538-4357/aba9d8

doi:10.3847/1538-4357/aba9d8 2020

[7] [7]

L., Madore, B

Freedman, W. L., Madore, B. F., Jang, I. S., et al. 2024, arXiv e-prints, arXiv:2408.06153, doi: 10.48550/arXiv.2408.06153

arXiv doi:10.48550/arxiv.2408.06153 2024

[8] [8]

A., Rizzi, L., Tully, R

Jacobs, B. A., Rizzi, L., Tully, R. B., et al. 2009, AJ, 138, 332, doi: 10.1088/0004-6256/138/2/332

doi:10.1088/0004-6256/138/2/332 2009