The cosmic distance scale based on near-infrared observations of Type II and Anomalous Cepheids

Classical Cepheids (CCs) are the young,massive,pulsating stars that have been established as the primary calibrators of the distance ladder for measuring H0 in the local Universe.The Cepheid variables class also includes Type II (T2Cs) and Anomalous Cepheids (ACs).These less massive and more metal-poor stars are relatively frequent in dwarf galaxies and the Milky Way.Every class of Cepheid obeys a different Period Luminosity (PL) and Period Wesenheit (PW) relation,which are particularly tight in near-infrared bands.In the era of the Hubble tension,AC and T2C variables together with the RRLyr stars and the tip of the red giant branch can potentially provide non-CC-dependent calibration of the Cosmic Distance Ladder.We present new accurate multi-wavelength PL\PW relations for T2Cs subclasses and ACs in the Magellanic Clouds (MCs).We adopted literature optical photometry from the OGLE and the Gaia surveys,while for the near-infrared we took advantage of data collected in the context of the VISTA near-infrared survey of the Magellanic Clouds System.We analyzed YJKs time-series for over 500 ACs and T2Cs in the MCs.The derived PL/PW relations were adopted to estimate the distances of several stellar systems in the Local Group.The comparison between distances based on ACs and T2Cs PL/PW relations and based on other classical pulsators,such as CCs and RRLyr stars,shows good agreement.This strengthens the case for the Hubble tension,independently from the details of the cosmic ladder.