A Cepheid-based Distance to the Type 1 Seyfert NGC 3783

Abstract

We present a Cepheid-based distance to the Type 1 Seyfert NGC 3783 using the Hubble Space Telescope. Images were obtained over 15 visits using nonredundant time spacing, with ten observations in the F350LP filter and eight observations each in the F555W and F814W filters. We found 1541 unique point sources across all observations, and we fit Cepheid templates to analyze these light curves. From these data, we determined a full sample of seven Cepheid candidates. Of these seven candidates, four are the most convincing and comprise our "strong" sample of Cepheid candidates. We fit the period$-$luminosity relationship to the total sample and to our "strong" sample using the LMC calibration by Riess et al. (2019). Adopting an independent distance constraint to the LMC given by Pietrzynski et al. (2019), and correcting for the potential effects of metallicity, we determine a distance modulus of $μ= 33.118 \pm 0.154$ mag using our strong sample. This value is formally consistent with the value derived using our full sample and corresponds to a distance of $D = 42.03 \pm 2.98$ Mpc. NGC 3783 is therefore among the farthest galaxies with a Cepheid-based distance measurement.