The Tip of the Red Giant Branch as a Distance Indicator for Resolved Galaxies

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.