The ages of the oldest stellar objects in our galaxy provide an independent test of the current cosmological model as they give a lower limit to the age of the Universe. Recent accurate parallaxes by the Gaia space mission, accurate measurements of the metallicity of stars, via individual elemental abundances, and advances in the modelling of stellar evolution, provide new, higher-precision age estimates of the oldest stellar populations in the galaxy: globular clusters and very-low-metallicity stars. The constraints on the age of the Universe, t U , so obtained are determined from the local Universe and at late time. It is well known that local and early-Universe determinations of another cosmological parameter closely related to the age of the Universe, the Hubble constant H 0 , show a3 σ tension. In the standard cosmological model, ΛCDM, t U and H 0 are related by the matter density parameter Ω m,0 . We propose to combine local t U constraints with late-time Ω m,0 estimates in a ΛCDM framework, to obtain a low-redshift H 0 determination that does not rely on early Universe physics. A proof-of-principle of this approach with current data gives H 0 =71±2.8 (H 0 = 69.3 ± 2.7) km s -1 Mpc -1 from globular clusters (very-low-metallicity stars) with excellent prospects for improved constraints in the near future.

The local and distant Universe: stellar ages and H0

Cimatti A.
Writing – Review & Editing
;
Moresco M.
Membro del Collaboration Group
;
2019

Abstract

The ages of the oldest stellar objects in our galaxy provide an independent test of the current cosmological model as they give a lower limit to the age of the Universe. Recent accurate parallaxes by the Gaia space mission, accurate measurements of the metallicity of stars, via individual elemental abundances, and advances in the modelling of stellar evolution, provide new, higher-precision age estimates of the oldest stellar populations in the galaxy: globular clusters and very-low-metallicity stars. The constraints on the age of the Universe, t U , so obtained are determined from the local Universe and at late time. It is well known that local and early-Universe determinations of another cosmological parameter closely related to the age of the Universe, the Hubble constant H 0 , show a3 σ tension. In the standard cosmological model, ΛCDM, t U and H 0 are related by the matter density parameter Ω m,0 . We propose to combine local t U constraints with late-time Ω m,0 estimates in a ΛCDM framework, to obtain a low-redshift H 0 determination that does not rely on early Universe physics. A proof-of-principle of this approach with current data gives H 0 =71±2.8 (H 0 = 69.3 ± 2.7) km s -1 Mpc -1 from globular clusters (very-low-metallicity stars) with excellent prospects for improved constraints in the near future.
Jimenez R.; Cimatti A.; Verde L.; Moresco M.; Wandelt B.
File in questo prodotto:
File Dimensione Formato  
11585_732010_postprint.pdf

accesso aperto

Tipo: Postprint
Licenza: Licenza per accesso libero gratuito
Dimensione 488.98 kB
Formato Adobe PDF
488.98 kB Adobe PDF Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11585/732010
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 26
  • ???jsp.display-item.citation.isi??? 28
social impact