The Carnegie Chicago Hubble Program. VI. Tip of the Red Giant Branch Distances to M66 and M96 of the Leo I Group
Madore, Barry F.; Freedman, Wendy L.; Beaton, Rachael L.; Lee, Myung Gyoon; Jang, In Sung; Monson, Andrew J.; Neeley, Jillian R.; Mager, Violet A.; Rich, Jeffrey A.; Hatt, Dylan; Hoyt, Taylor J.
United States, Germany, South Korea
Abstract
We determine the distances to the Type Ia supernova host galaxies M66 (NGC 3627) and M96 (NGC 3368) of the Leo I Group using the Tip of the Red Giant Branch (TRGB) method. We target the stellar halos of these galaxies using the Hubble Space Telescope ACS/WFC in the F606W and F814W bandpasses. By pointing to the stellar halos we sample RGB stars predominantly of Population II, minimize host-galaxy reddening, and significantly reduce the effects of source crowding. Our absolute calibration of the I-band TRGB is based on a recent detached eclipsing binary distance to the Large Magellanic Cloud. With this geometric zero-point in hand, we find for M66 and M96, respectively, true distance moduli μ 0 = 30.23 ± 0.04 (stat) ± 0.06 (sys) mag and μ 0 = 30.29 ± 0.02 (stat) ± 0.06 (sys) mag.