2026ApJ..1000...78M

We present Cepheid-based distances to two canonical active galactic nuclei: NGC 4303 (M61) and NGC 1068. Data were obtained using the Hubble Space Telescope with nonredundant time spacing over 12 visits for each target, and observations were made with the F555W and F814W filters. We found 32,694 point sources in NGC 4303, and 130 of these were determined to be strong Cepheid candidates with periods ranging from ∼13 to 93 days. In NGC 1068, we found 20,207 point sources, where 51 of these were strong Cepheid candidates with periods of ∼14-92 days. We fit the period-luminosity relationship, calibrated based on a geometric distance to the LMC by A. G. Riess et al., to our Cepheid candidates in each galaxy and correct for potential effects of metallicity. Using a distance constraint for the LMC given by G. Pietrzyński et al., this yields a distance modulus of μ = 31.083 ± 0.035 mag for NGC 4303 and μ = 30.150 ± 0.106 mag for NGC 1068. Thus, we measure distances of D = 16.47 ± 0.27 Mpc to NGC 4303 and D = 10.72 ± 0.52 Mpc to NGC 1068.