Supercooled phase transitions in conformal dark sectors explain NANOGrav data

According to recent lore, supercooled first-order phase transitions (FOPTs) cannot explain the evidence for a stochastic gravitational wave background obtained by pulsar timing arrays. We demonstrate that supercooled FOPTs in Majoron-like U(1)' models with a conformal dark sector easily explain the nHz signal at NANOGrav in conjunction with the observed pattern of active neutrino masses and mixing. We find that models with a U(1)' charge of the Higgs doublet close to that of the B-L model are favored.