Revisiting oldest stars as cosmological probes: new constraints on the Hubble constant

Abstract

Despite the tremendous advance of observational cosmology, the value of the Hubble constant (H 0 ) is still controversial (the so called "Hubble tension") because of the inconsistency between local/late-time measurements and those derived from the cosmic microwave background. As the age of the Universe is very sensitive to H 0 , we explored whether the present-day oldest stars could place independent constraints on the Hubble constant. To this purpose, we selected from the literature the oldest objects (globular clusters, stars, white dwarfs, ultra-faint and dwarf spheroidal galaxies) with accurate age estimates. Adopting a conservative prior on their formation redshifts (11 ≤ z f ≤ 30) and assuming Ω M = 0.3 ± 0.02, we developed a method based on Bayesian statistics to estimate the Hubble constant. We selected the oldest objects (> 13.3 Gyr), and estimated H 0 both for each of them individually and for the average ages of homogeneous subsamples. Statistical and systematic uncertainties were properly taken into account. The constraints based on individual ages indicate that H 0 < 70.6 km/s/Mpc when selecting the most accurate estimates. If the ages are averaged and analyzed independently for each subsample, the most stringent constraints imply H 0 < 73.0 with a probability of 93.2% and errors around 2.5 km/s/Mpc. We also constructed an "accuracy matrix" to assess how the constraints on H 0 become more stringent with further improvements in the accuracy of stellar ages and Ω M . The results show the high potential of the oldest stars as independent and competitive cosmological probes.

Seven Hints That Early-Time New Physics Alone Is Not Sufficient to Solve the Hubble Tension

“…For further related works, see Refs. [589][590][591], and Ref. [592] for a discussion in the context of the related look-back time quantity.…”

A Critical Discussion on the H0 Tension

“…Other important measurable quantities for the cosmological studies are the look-back time and the related age of the Universe, which have been used to infer H 0 observationally, as it is the case of the ages of the observed astrophysical objects [155,[191][192][193][194][195].…”

Negative cosmological constant in the dark energy sector: tests from JWST photometric and spectroscopic observations of high-redshift galaxies

“…Various tests of DE on astrophysical, astronomical, and even local scales, have been considered over the past decades, see refs [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. for examples in this sense.3 Distant galaxies are also useful as a test of cosmological models through their ages, which of course cannot exceed the age of the Universe: see for instance refs [32][33][34][35][36][37][38]. for recent works exploring the important of stellar and galactic ages as a test of cosmological models 4.…”