SIMBAD references

We present new evidence for the extragalactic Cepheid distance bias. A dependence between the Hubble parameter and the absolute Cepheid magnitude limit for a galaxy may be interpreted as a significant bias in the derived photometric distances: those from Cepheid samples with a bright absolute magnitude limit apparently are underestimated. This may be caused not only by the dispersion of M at a fixed Cepheid period, but also by the whole amplitude of variation, together with an upper limit in the period of the observed Cepheids, and other factors. If so, then the value of H₀ based on methods using Cepheid distances is expected to be often overestimated (i.e. the distances underestimated). We discuss whether the effect could be not real, but rather caused by uncertainties in kinematical distances.