On the Population II Distance Scale: Tip of the Red Giant Branch Distances to Local Galaxies

The difference between direct and indirect measures of H0, i.e. via SNe Ia distances anchored by Cepheids and via modeling of the Cosmic Microwave Background, stands at an average >3-sigma. This tension has motivated a second look at the calibration of the extragalactic distance scale. Population II stars have gained favor as an independent calibrator of SNe Ia, bypassing the possible systematics associated with the traditional Cepheid-based distances. We present high-fidelity distances to four local galaxies---IC 1613, NGC 4424, NGC 4526, and NGC4536---using the Tip of the Red Giant Branch, which is a prominent observable that is defined by well-understood stellar astrophysics. We further compare these results with existing Cepheid-based distances and demonstrate a good correspondence between distances derived from stars of Population I and II.