Metallicity-corrected Tip of the Red Giant Branch Distance to NGC 4258

Understand

We have determined the distance to NGC 4258 using observations made with the Hubble Space Telescope (HST) and the Wide Field, Advanced Camera for Surveys (ACS/WFC).

• We apply a modified technique that fully accounts for metallicity effects on the use of the luminosity of the tip of the red giant branch (TRGB) to determine one of the most precise TRGB distance moduli to date: u(TRGB) = 29.28 +/- 0.04 (random) +/- 0.12 (systematic) mag (7.18 +/- 0.13 +/- 0.40 Mpc).
• We discuss this distance modulus with respect to other recent applications of the TRGB method to NGC 4258, and with several other techniques (Cepheids and masers) that are equally competitive in their precision, but different in their systematics.