The Hubble Constant from Type Ia Supernovae Calibrated with the Linear and Nonlinear Cepheid Period-Luminosity Relations

It is well known that the peak brightness of Type Ia supernovae calibrated with Cepheid distances can be used to determine the Hubble constant. The Cepheid distances to the host galaxies of the calibrating supernovae are usually obtained using the period-luminosity (P-L) relation derived from Large Magellanic Cloud (LMC) Cepheids. However, recent empirical studies provide evidence that the LMC P-L relation is not linear. Here we determine the Hubble constant using both the linear and nonlinear LMC Cepheid P-L relations as calibrating relations to four galaxies that hosted Type Ia supernovae. Our results suggest that the obtained values of the Hubble constant are similar. However, a typical error of ~0.03 mag has to be added (in quadrature) to the systematic error for the Hubble constant when the linear LMC P-L relation is used, assuming that the LMC P-L relation is indeed nonlinear. This is important to minimize the total error on the Hubble constant in the era of precision cosmology. The Hubble constants calibrated from the linear and nonlinear LMC P-L relations are H₀ = 74.92 ± 2.28 (random) ± 5.06 (systematic) km s^-1 Mpc^-1 and H₀ = 74.37 ± 2.27 (random) ± 4.92 (systematic) km s^-1 Mpc^-1, respectively. Hubble constants calculated using the Galactic P-L relation are also presented and briefly discussed.