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Doubly Discordant SH0ES NGC4258 Cepheid Relations (HVI), and Impactful Extinction Laws

Astrophysics of Galaxies 2025-10-07 v1 Cosmology and Nongalactic Astrophysics

Abstract

SH0H_0ES 2016-2022 HVIHVI data for classical Cepheids in the keystone galaxy NGC4258 yield doubly discordant Wesenheit Leavitt functions:~ΔW0,HVI=0.13±0m.02\Delta W_{0,H-VI} = -0.13\pm0^{m}.02 (0m.17-0^{m}.17 unweighted) and that is paired with a previously noted ΔW0,IVI0m.3\Delta W_{0,I-VI}\simeq-0^{m}.3, which in concert with complimentary evidence suggest the 2016 SH0H_0ES NGC4258-anchored H0±σH0H_0 \pm \sigma_{H_0} warrants scrutiny (i.e., σH0/H06\sigma_{H_0}/{H_0}\gtrsim 6\%). Cepheid distance uncertainties are further exacerbated by extinction law ambiguities endemic to such Leavitt relations (e.g., NGC4258), particularly for comparatively obscured variables (e.g., Δd4\Delta d \gtrsim 4\%, reddened Cepheid subsamples in the Milky Way, M31, NGC2442, NGC4424, NGC5643, NGC7250). Lastly, during the analysis it was identified that the 2022 SH0H_0ES database relays incorrect SMC Cepheid photometry.

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Cite

@article{arxiv.2510.04998,
  title  = {Doubly Discordant SH0ES NGC4258 Cepheid Relations (HVI), and Impactful Extinction Laws},
  author = {Daniel Majaess},
  journal= {arXiv preprint arXiv:2510.04998},
  year   = {2025}
}

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