Probing the formation of the first low-mass stars with stellar archaeology

Frebel, Anna; Johnson, Jarrett L.; Bromm, Volker

doi:10.1111/j.1745-3933.2007.00344.x

Cited by 215 publications

(245 citation statements)

References 59 publications

(86 reference statements)

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“…The star SDSS J102915+172927 (RA = 10h 29m 15.15s and declination =+17° 29 ' 28 7,16 , but it strongly supports the idea that, at least in some cases, low mass stars can also form at lower carbon and oxygen abundances than the current estimates for the critical values.…”

mentioning

confidence: 48%

An extremely primitive star in the Galactic halo

Caffau¹,

Bonifacio²,

François³

et al. 2011

Nature

320

376

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The early Universe had a chemical composition consisting of hydrogen, helium and traces of lithium 1 , almost all other elements were created in stars and supernovae. The mass fraction, Z, of elements more massive than helium, is called "metallicity". A number of very metal poor stars have been found 2,3 , some of which, while having a low iron abundance, are rich in carbon, nitrogen and oxygen 4,5,6 . For theoretical reasons 7,8 and because of an observed absence of stars with metallicities lower than Z=1.5×10 5 , it has been suggested that low mass stars (M‹0.8M ⊙ , the ones that survive to the present day) cannot form until the interstellar medium has been enriched above a critical value, estimated to lie in the range 1.5×10 8 ≤Z≤1.5×10 6[8] , although competing * Gliese Fellow

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mentioning

confidence: 48%

An extremely primitive star in the Galactic halo

Caffau¹,

Bonifacio²,

François³

et al. 2011

Nature

320

376

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“…The critical metallicity at which the transition in the IMF takes place is uncertain, but cosmological simulations suggest that Pop III supernovae quickly boost the local metallicity above the critical metallicity, so the onset of Pop II star formation does not depend sensitively on this choice (Maio et al 2010(Maio et al , 2011. We choose a critical metallicity of Zcrit = 10 −4 Z , with Z = 0.02, a value roughly consistent with both theory (Bromm et al 2001;Schneider et al 2002) and the inferred metallicities of metal-poor stars (Frebel et al 2007;Caffau et al 2011). …”

Section: Star Formationmentioning

confidence: 99%

The First Billion Years project: the escape fraction of ionizing photons in the epoch of reionization

Paardekooper

Khochfar

Vecchia

2015

Monthly Notices of the Royal Astronomical Society

244

280

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Proto-galaxies forming in low-mass dark matter haloes are thought to provide the majority of ionizing photons needed to reionize the Universe, due to their high escape fractions of ionizing photons. We study how the escape fraction in high-redshift galaxies relates to the physical properties of the halo in which the galaxies form, by computing escape fractions in more than 75000 haloes between redshifts 27 and 6 that were extracted from the First Billion Years project, high-resolution cosmological hydrodynamics simulations of galaxy formation. We find that the main constraint on the escape fraction is the gas column density in a radius of 10 pc around the stellar populations, causing a strong mass dependence of the escape fraction. The lower potential well in haloes with M 200 10 8 M results in low column densities that can be penetrated by radiation from young stars (age < 5 Myr). In haloes with M 200 10 8 M supernova feedback is important, but only ∼ 30% of the haloes in this mass range have an escape fraction higher than 1%. We find a large range of escape fractions in haloes with similar properties, caused by different distributions of the dense gas in the halo. This makes it very hard to predict the escape fraction on the basis of halo properties and results in a highly anisotropic escape fraction. The strong mass dependence, the large spread and the large anisotropy of the escape fraction may strongly affect the topology of reionization and is something current models of cosmic reionization should strive to take into account.

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“…They also point out that, in order to sample individual supernova events occurring in the earliest epochs, the best candidates among these second generation stars would be those with abundances of carbon and oxygen very close to this critical metallicity. Frebel et al (2007) predict that all stars with [Fe/H] < −4 should show enhanced C and/or O abundances, because otherwise they would not have lived long enough (have low enough mass) to be observed.…”

Section: Introductionmentioning

confidence: 99%

The C/O ratio at low metallicity: constraints on early chemical evolution from observations of Galactic halo stars

Fabbian

Nissen

Asplund

et al. 2009

A&A

101

130

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Aims. We present new measurements of the abundances of carbon and oxygen derived from high-excitation C i and O i absorption lines in metal-poor halo stars, with the aim of clarifying the main sources of these two elements in the early stages of the chemical enrichment of the Galaxy. Methods. We target 15 new stars compared to our previous study, with an emphasis on additional C/O determinations in the crucial metallicity range −3 < ∼ [Fe/H] < ∼ −2. The stellar effective temperatures were estimated from the profile of the Hβ line. Departures from local thermodynamic equilibrium were accounted for in the line formation for both carbon and oxygen. The non-LTE effects are very strong at the lowest metallicities but, contrary to what has sometimes been assumed in the past due to a simplified assessment, of different degrees for the two elements. In addition, for the 28 stars with [Fe/H] < −1 previously analysed, stellar parameters were re-derived and non-LTE corrections applied in the same fashion as for the rest of our sample, giving consistent abundances for 43 halo stars in total.

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Probing the formation of the first low-mass stars with stellar archaeology

Cited by 215 publications

References 59 publications

An extremely primitive star in the Galactic halo

An extremely primitive star in the Galactic halo

The First Billion Years project: the escape fraction of ionizing photons in the epoch of reionization

The C/O ratio at low metallicity: constraints on early chemical evolution from observations of Galactic halo stars

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