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We derive a distance of D = 16.6 ± 0.3 Mpc (μ = 31.10 ± 0.04 mag) to the archetypal narrow-line Seyfert 1 galaxy NGC 4051 based on Cepheid period–luminosity relations and new Hubble Space Telescope multiband imaging. We identify 419 Cepheid candidates and estimate the distance at both optical and near-infrared wavelengths using subsamples of precisely photometered variables (123 and 47 in the optical and near-infrared subsamples, respectively). We compare our independent photometric procedures and distance-estimation methods to those used by the Supernovae, H0, for the Equation of State team and find agreement to 0.01 mag. The distance we obtain suggests an Eddington ratio of for NGC 4051, typical of narrow-line Seyfert 1 galaxies, unlike the seemingly odd value implied by previous distance estimates. We derive a peculiar velocity of −490 ± 34 km s−1 for NGC 4051, consistent with the overall motion of the Ursa Major Cluster in which it resides. We also revisit the energetics of the NGC 4051 nucleus, including its outflow and mass accretion rates. [ABSTRACT FROM AUTHOR]

We derive a distance of 15.8 ± 0.4 Mpc to the archetypal Seyfert 1 galaxy NGC 4151 based on the near-infrared Cepheid period–luminosity relation and new Hubble Space Telescope multiband imaging. This distance determination, based on measurements of 35 long-period (P > 25 days) Cepheids, will support the absolute calibration of the supermassive black hole mass in this system, as well as studies of the dynamics of the feedback or feeding of its active galactic nucleus. [ABSTRACT FROM AUTHOR]

We identify and phase a sample of 81 Cepheids in the maser-host galaxy NGC 4258 using the Large Binocular Telescope, and obtain calibrated mean magnitudes in up to four filters for a subset of 43 Cepheids using archival Hubble Space Telescope data. We employ three models to study the systematic effects of extinction, the assumed extinction law, and metallicity on the Cepheid distance to NGC 4258. We find a correction to the Cepheid colours consistent with a greyer extinction law in NGC 4258 compared to the Milky Way (RV = 4.9-0.7+0.9), although we believe this is indicative of other systematic effects. If we combine our Cepheid sample with previously known Cepheids, we find a significant metallicity adjustment to the distance modulus of γ1 = -0.61 ± 0.21 mag dex-1 for the Zaritsky et al. metallicity scale, as well as a weak trend of Cepheid colours with metallicity. Conclusions about the absolute effect of metallicity on Cepheid mean magnitudes are limited by the available data on the metallicity gradient in NGC 4258, but our Cepheid data require at least some metallicity adjustment to make the Cepheid distance consistent with independent distances to the Large Magellanic Cloud (LMC) and NGC 4258. From our ensemble of models and the geometric maser distance of NGC 4258 (μN4258 = 29.40 ± 0.06 mag), we estimate μLMC = 18.57 ± 0.14 mag (51.82 ± 3.23 kpc), including the uncertainties due to metallicity. [ABSTRACT FROM AUTHOR]