Papers › Comparative Analysis of TRGBs (CATs) from Unsupervised, Multi-Halo-Field Measurements:...
Comparative Analysis of TRGBs (CATs) from Unsupervised, Multi-Halo-Field Measurements: Contrast is Key
J. Wu, D. Scolnic, A. G. Riess, G. S. Anand, R. Beaton, S. Casertano, X. Ke, S. Li
The archive published only this paper's code-link row. Authors, date and abstract are from arXiv's metadata (CC0), read from the Kaggle arXiv metadata snapshot of 2026-09-12 where its title matched the archive's; the title is the archive's.
The Tip of the Red Giant Branch (TRGB) is an apparent discontinuity in the color-magnitude diagram (CMD) along the giant branch due to the end of the red giant evolutionary phase and is used to measure distances in the local universe. In practice, the tip is often fuzzy and its localization via edge detection response (EDR) relies on several methods applied on a case-by-case basis. It is hard to evaluate how individual choices affect a distance estimation using only a single host field while also avoiding confirmation bias. To devise a standardized approach, we compare unsupervised, algorithmic analyses of the TRGB in multiple halo fields per galaxy, up to 11 fields for a single host and 50 fields across 10 galaxies, using high signal-to-noise stellar photometry obtained by the GHOSTS survey with the Hubble Space Telescope. We first optimize methods for the lowest field-to-field dispersion including spatial filtering to remove star forming regions, smoothing and weighting of the luminosity function, selection of the RGB by color, and tip selection based on the number of likely RGB stars and the ratio of stars above versus below the tip (R). We find R, which we call the tip `contrast', to be the most important indicator of the quality of EDR measurements; we find that field-to-field EDR repeatability varies from 0.3 mag to ≤ 0.05 mag for R=4 to 7, respectively, though less than half the fields reach the higher quality. Further, we find that R, which varies with the age/metallicity of the stellar population based on models, correlates with the magnitude of the tip (and after accounting for low internal extinction), i.e., a tip-contrast relation with slope of -0.023±0.0046 mag/ratio, a ∼5σ result that improves standardization of the TRGB. We discuss the value of consistent TRGB standardization across rungs for robust distance ladder measurements.
Code
Repository list and official/mentioned flags are the archive's, frozen 2025-07-28. Reachability, where shown, is from one Syntology probe window (2026-09-16 to 2026-09-18); repositories not probed show nothing. GitHub stars are not tracked.
Code Syntology ran Syntology
Not run by Syntology. Nothing on this page verifies that the listed code works.
Results from the paper archive 2025-07-28
No leaderboard rows for this paper in the archive.
Report a problem or propose a change · a person checks every report against the paper or source before anything changes; decisions are listed on /corrections