Primordial Helium-3 Redux: The Helium Isotope Ratio of the Orion Nebula - Archive ouverte HAL
Article Dans Une Revue The Astrophysical Journal Année : 2022

Primordial Helium-3 Redux: The Helium Isotope Ratio of the Orion Nebula

Ryan J. Cooke
  • Fonction : Auteur
James W. Johnson
  • Fonction : Auteur
Max Pettini
  • Fonction : Auteur
Louise Welsh
  • Fonction : Auteur
Michael T. Murphy
  • Fonction : Auteur
David H. Weinberg
  • Fonction : Auteur

Résumé

We report the first direct measurement of the helium isotope ratio, $^{3}$He/$^{4}$He, outside of the Local Interstellar Cloud, as part of science-verification observations with the upgraded CRyogenic InfraRed Echelle Spectrograph. Our determination of $^{3}$He/$^{4}$He is based on metastable He i* absorption along the line of sight toward Θ$^{2}$A Ori in the Orion Nebula. We measure a value $^{3}$He/$^{4}$He = (1.77 ± 0.13) × 10$^{−4}$, which is just ∼40% above the primordial relative abundance of these isotopes, assuming the Standard Model of particle physics and cosmology, ($^{3}$He/$^{4}$He)$_{p}$ = (1.257 ± 0.017) × 10$^{−4}$. We calculate a suite of galactic chemical evolution simulations to study the Galactic build up of these isotopes, using the yields from Limongi & Chieffi for stars in the mass range M = 8–100 M $_{⊙}$ and Lagarde et al. for M = 0.8–8 M $_{⊙}$. We find that these simulations simultaneously reproduce the Orion and protosolar $^{3}$He/$^{4}$He values if the calculations are initialized with a primordial ratio . Even though the quoted error does not include the model uncertainty, this determination agrees with the Standard Model value to within ∼2σ. We also use the present-day Galactic abundance of deuterium (D/H), helium (He/H), and $^{3}$He/$^{4}$He to infer an empirical limit on the primordial $^{3}$He abundance, , which also agrees with the Standard Model value. We point out that it is becoming increasingly difficult to explain the discrepant primordial $^{7}$Li/H abundance with nonstandard physics, without breaking the remarkable simultaneous agreement of three primordial element ratios (D/H, $^{4}$He/H, and $^{3}$He/$^{4}$He) with the Standard Model values.
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hal-03632157 , version 1 (08-04-2023)

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Ryan J. Cooke, Pasquier Noterdaeme, James W. Johnson, Max Pettini, Louise Welsh, et al.. Primordial Helium-3 Redux: The Helium Isotope Ratio of the Orion Nebula. The Astrophysical Journal, 2022, 932 (1), pp.60. ⟨10.3847/1538-4357/ac6503⟩. ⟨hal-03632157⟩
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