Abstract Observations with JWST in the F090W band provide a powerful tool for determining galaxy distances based on tip of the red giant branch (TRGB) measurements. It is a great convenience that the TRGB lies at an almost constant absolute magnitude level at low metallicities. However, the TRGB becomes fainter at high metallicities in the F090W filter. Details of this break in slope are critical for precision applications in the acquisition of distances. With an absolute scaling set by the maser distance to NGC 4258 (but excluding the uncertainty in that distance), the value M F090W TRGB = − 4.40 ± 0.03 mag (traditional Vega) is found for (F090W − F150W) 0 < 1.65 mag. The theoretical RGB isochrone that reaches the color 1.65 at the RGB tip corresponds to metallicity M/H = −0.57 for a 10 Gyr population. The calibration is used to derive distances for 16 galaxies relative to the megamaser host NGC 4258. Revised distances are on average slightly closer than literature values derived from the same data.
Chazov et al. (2026) studied this question.