Absolute Calibration of Cluster Mira Variables to Provide a New Anchor for the Hubble Constant Determination

Abstract Mira variables in globular clusters can provide an accurate and precise absolute calibration of their period–luminosity relations (PLRs) to independently anchor the cosmic distance scale and determine the Hubble constant. We present homogeneous near-infrared ( JHK s ) time-series photometric observations of a sample of 55 candidate long-period variables in 18 globular clusters covering a wide metallicity range (−1.7 < [Fe/H] < − 0.1 dex). The Gaia proper motions, long-period variability information, and optical-infrared colors are used to identify 41 oxygen-rich Miras as members of the globular clusters. Mean luminosities of Miras in the JHK s bands are independently calibrated using the recommended distances and mean parallaxes to their host clusters. Cluster Mira PLRs exhibit scatter comparable to the Large Magellanic Cloud (LMC) variables and do not show any dependence on iron abundance for a wide range of metallicities. We establish the accuracy of cluster Miras as independent anchors by determining a distance modulus to the LMC, 18.45 ± 0.04 mag, in agreement with the 1.2% precise geometric distance. Our H -band photometry is transformed to derive Hubble Space Telescope F160W PLR for cluster Miras, providing a three-anchor baseline with the LMC and NGC 4258. We employ a three-anchor solution to determine distances to two type Ia supernovae host galaxies, NGC 1559 (31.39 ± 0.05 mag) and M101 (29.07 ± 0.04 mag), and provide a 3.7% measurement of the Hubble constant, H 0 = 73.06 ± 2.67 km s −1 Mpc −1 . Similar to Cepheids, our independent baseline solution results in a local H 0 determination that is systematically larger than its inference from the early universe probes, further supporting the ongoing Hubble tension.