The period--luminosity relation for Mira variables in the Milky Way using Gaia DR3: a further distance anchor for $H_0$

TL;DR

This study calibrates Mira variable period-luminosity relations using Gaia DR3 data, compares them across different galaxies, and applies them to measure the Hubble constant, providing a new distance anchor for cosmology.

Contribution

It introduces a probabilistic calibration of Mira period-luminosity relations with Gaia DR3, accounting for parallax systematics and population effects, and applies these relations to estimate H_0.

Findings

Milky Way Mira relations are slightly steeper than LMC.

Gaia parallaxes are unbiased on average but have underestimated uncertainties.

Derived H_0 value is 73.7 km/s/Mpc with 4.4 km/s/Mpc uncertainty.

Abstract

Gaia DR3 parallaxes are used to calibrate preliminary period--luminosity relations of O-rich Mira variables in the 2MASS $J$, $H$ and $K_s$ bands using a probabilistic model accounting for variations in the parallax zeropoint and underestimation of the parallax uncertainties. The derived relations are compared to those measured for the Large and Small Magellanic Clouds, the Sagittarius dwarf spheroidal galaxy, globular cluster members and the subset of Milky Way Mira variables with VLBI parallaxes. The Milky Way linear $JHK_s$ relations are slightly steeper and thus fainter at short period than the corresponding LMC relations suggesting population effects in the near-infrared are perhaps larger than previous observational works have claimed. Models of the Gaia astrometry for the Mira variables suggest that, despite the intrinsic photocentre wobble and use of mean photometry in the astrometric solution of the current data reduction, the recovered parallaxes should be on average unbiased but with underestimated uncertainties for the nearest stars. The recommended Gaia EDR3 parallax zeropoint corrections evaluated at $\nu_\mathrm{eff}=1.25\,\mu\mathrm{m}^{-1}$ require minimal ($\lesssim5\,\mu\mathrm{as}$) corrections for redder five-parameter sources, but over-correct the parallaxes for redder six-parameter sources, and the parallax uncertainties are underestimated, at most by a factor $\sim1.6$ at $G\approx12.5\,\mathrm{mag}$. The derived period--luminosity relations are used as anchors for the Mira variables in the Type Ia host galaxy NGC 1559 to find $H_0=(73.7\pm4.4)\,\mathrm{km\,s}^{-1}\mathrm{Mpc}^{-1}$.