The<i>Hubble Space Telescope</i>Key Project on the Extragalactic Distance Scale. XXV. A Recalibration of Cepheid Distances to Type Ia Supernovae and the Value of the Hubble Constant
Bibliographic record
Abstract
Cepheid-based distances to seven Type Ia supernovae (SNe) host galaxies have been derived using the standard Hubble Space Telescope ( HST ) Key Project on the Extragalactic Distance Scale pipeline. For the first time, this allows for a transparent comparison of data accumulated as part of three different HST projects: the Key Project, the Sandage et al. Type Ia supernovae (SNe) program, and the Tanvir et al. Leo I Group study. Reanalyzing the Tanvir et al. galaxy and six Sandage et al. galaxies, we find a mean (weighted) offset in true distance moduli of 0.12 ± 0.07 mag; i.e., 6% in linear distance, in the sense of reducing the distance scale or increasing H 0 . Adopting the reddening-corrected Hubble relations of Suntzeff et al. tied to a zero point based on SNe 1990N, 1981B, 1998bu, 1989B, 1972E, and 1960F and the photometric calibration of Hill et al. leads to a Hubble constant of H 0 = 68 ± 2(random) ± 5(systematic) km s -1 Mpc -1 . Adopting the Kennicutt et al. Cepheid period-luminosity-metallicity dependency decreases the inferred H 0 by 4%. The H 0 result from Type Ia SNe is now in good agreement, to within their respective uncertainties, with that from the Tully-Fisher and surface brightness fluctuation relations.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.003 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.022 | 0.014 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".