The cosmological lithium problem outside the Galaxy: The sagittarius globular cluster M54*

A. Mucciarelli, M. Salaris, P. Bonifacio, L. Monaco, S. Villanova

Resultado de la investigación: Article

8 Citas (Scopus)

Resumen

The cosmological Li problem is the observed discrepancy between Li abundance (A(Li)) measured in Galactic dwarf, old and metal-poor stars (traditionally assumed to be equal to the initial value A(Li)0), and that predicted by standard big bang nucleosynthesis (BBN) calculations (A(Li)BBN). Here, we attack the Li problem by considering an alternative diagnostic, namely the surface Li abundance of red giant branch stars that in a colour-magnitude diagram populate the region between the completion of the first dredge-up and the red giant branch bump. We obtained high-resolution spectra with the FLAMES facility at the Very Large Telescope for a sample of red giants in the globular clusterM54, belonging to the Sagittarius dwarf galaxy. We obtain A(Li) = 0.93 ± 0.11 dex, translating - after taking into account the dilution due to the dredge-up - to initial abundances (A(Li)0) in the range 2.35-2.29 dex, depending on whether or not atomic diffusion is considered. This is the first measurement of Li in the Sagittarius galaxy and the more distant estimate of A(Li)0 in old stars obtained so far. The A(Li)0 estimated in M54 is lower by∼0.35 dex than A(Li)BBN, hence incompatible at a level of ∼3σ. Our result shows that this discrepancy is a universal problem concerning both the Milky Way and extragalactic systems. Either modifications of BBN calculations, or a combination of atomic diffusion plus a suitably tuned additional mixing during the main sequence, need to be invoked to solve the discrepancy.

Idioma originalEnglish
Páginas (desde-hasta)1812-1820
Número de páginas9
PublicaciónMonthly Notices of the Royal Astronomical Society
Volumen444
N.º2
DOI
EstadoPublished - 2014

Huella dactilar

lithium
globular clusters
nuclear fusion
dredger
galaxies
stars
translating
color-magnitude diagram
dilution
dwarf galaxies
diagram
attack
metal
telescopes
high resolution
estimates
metals
calculation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Citar esto

Mucciarelli, A. ; Salaris, M. ; Bonifacio, P. ; Monaco, L. ; Villanova, S. / The cosmological lithium problem outside the Galaxy : The sagittarius globular cluster M54*. En: Monthly Notices of the Royal Astronomical Society. 2014 ; Vol. 444, N.º 2. pp. 1812-1820.
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abstract = "The cosmological Li problem is the observed discrepancy between Li abundance (A(Li)) measured in Galactic dwarf, old and metal-poor stars (traditionally assumed to be equal to the initial value A(Li)0), and that predicted by standard big bang nucleosynthesis (BBN) calculations (A(Li)BBN). Here, we attack the Li problem by considering an alternative diagnostic, namely the surface Li abundance of red giant branch stars that in a colour-magnitude diagram populate the region between the completion of the first dredge-up and the red giant branch bump. We obtained high-resolution spectra with the FLAMES facility at the Very Large Telescope for a sample of red giants in the globular clusterM54, belonging to the Sagittarius dwarf galaxy. We obtain A(Li) = 0.93 ± 0.11 dex, translating - after taking into account the dilution due to the dredge-up - to initial abundances (A(Li)0) in the range 2.35-2.29 dex, depending on whether or not atomic diffusion is considered. This is the first measurement of Li in the Sagittarius galaxy and the more distant estimate of A(Li)0 in old stars obtained so far. The A(Li)0 estimated in M54 is lower by∼0.35 dex than A(Li)BBN, hence incompatible at a level of ∼3σ. Our result shows that this discrepancy is a universal problem concerning both the Milky Way and extragalactic systems. Either modifications of BBN calculations, or a combination of atomic diffusion plus a suitably tuned additional mixing during the main sequence, need to be invoked to solve the discrepancy.",
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The cosmological lithium problem outside the Galaxy : The sagittarius globular cluster M54*. / Mucciarelli, A.; Salaris, M.; Bonifacio, P.; Monaco, L.; Villanova, S.

En: Monthly Notices of the Royal Astronomical Society, Vol. 444, N.º 2, 2014, p. 1812-1820.

Resultado de la investigación: Article

TY - JOUR

T1 - The cosmological lithium problem outside the Galaxy

T2 - The sagittarius globular cluster M54*

AU - Mucciarelli, A.

AU - Salaris, M.

AU - Bonifacio, P.

AU - Monaco, L.

AU - Villanova, S.

PY - 2014

Y1 - 2014

N2 - The cosmological Li problem is the observed discrepancy between Li abundance (A(Li)) measured in Galactic dwarf, old and metal-poor stars (traditionally assumed to be equal to the initial value A(Li)0), and that predicted by standard big bang nucleosynthesis (BBN) calculations (A(Li)BBN). Here, we attack the Li problem by considering an alternative diagnostic, namely the surface Li abundance of red giant branch stars that in a colour-magnitude diagram populate the region between the completion of the first dredge-up and the red giant branch bump. We obtained high-resolution spectra with the FLAMES facility at the Very Large Telescope for a sample of red giants in the globular clusterM54, belonging to the Sagittarius dwarf galaxy. We obtain A(Li) = 0.93 ± 0.11 dex, translating - after taking into account the dilution due to the dredge-up - to initial abundances (A(Li)0) in the range 2.35-2.29 dex, depending on whether or not atomic diffusion is considered. This is the first measurement of Li in the Sagittarius galaxy and the more distant estimate of A(Li)0 in old stars obtained so far. The A(Li)0 estimated in M54 is lower by∼0.35 dex than A(Li)BBN, hence incompatible at a level of ∼3σ. Our result shows that this discrepancy is a universal problem concerning both the Milky Way and extragalactic systems. Either modifications of BBN calculations, or a combination of atomic diffusion plus a suitably tuned additional mixing during the main sequence, need to be invoked to solve the discrepancy.

AB - The cosmological Li problem is the observed discrepancy between Li abundance (A(Li)) measured in Galactic dwarf, old and metal-poor stars (traditionally assumed to be equal to the initial value A(Li)0), and that predicted by standard big bang nucleosynthesis (BBN) calculations (A(Li)BBN). Here, we attack the Li problem by considering an alternative diagnostic, namely the surface Li abundance of red giant branch stars that in a colour-magnitude diagram populate the region between the completion of the first dredge-up and the red giant branch bump. We obtained high-resolution spectra with the FLAMES facility at the Very Large Telescope for a sample of red giants in the globular clusterM54, belonging to the Sagittarius dwarf galaxy. We obtain A(Li) = 0.93 ± 0.11 dex, translating - after taking into account the dilution due to the dredge-up - to initial abundances (A(Li)0) in the range 2.35-2.29 dex, depending on whether or not atomic diffusion is considered. This is the first measurement of Li in the Sagittarius galaxy and the more distant estimate of A(Li)0 in old stars obtained so far. The A(Li)0 estimated in M54 is lower by∼0.35 dex than A(Li)BBN, hence incompatible at a level of ∼3σ. Our result shows that this discrepancy is a universal problem concerning both the Milky Way and extragalactic systems. Either modifications of BBN calculations, or a combination of atomic diffusion plus a suitably tuned additional mixing during the main sequence, need to be invoked to solve the discrepancy.

KW - Globular clusters: Individual: M54

KW - Stars: Abundances

KW - Stars: Atmospheres

KW - Stars: Population II

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U2 - 10.1093/mnras/stu1522

DO - 10.1093/mnras/stu1522

M3 - Article

AN - SCOPUS:84929441214

VL - 444

SP - 1812

EP - 1820

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 2

ER -