We show that the I magnitude of the tip of the first-ascent red giant branch (TRGB) of low-mass stars is a distance indicator for resolved galaxies with metal-poor ([Fe/H] < -0.7 dex) old populations, having a precision comparable to primary distance indicators such as Cepheids and RR Lyraes. A comparison of the distances to resolved galaxies based on the TRGB with those derived from Cepheids and RR Lyraes shows that they agree within ‰0.1 mag. Advantages o{ the TRGB method are discussed.
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Lee et al. (1993) studied this question.