Oxygen-enhanced Extremely Metal-poor Damped Lyα Systems: A Signpost of the First Stars?

Welsh, Louise; Cooke, Ryan; Fumagalli, Michele

doi:10.3847/1538-4357/ac4503

Cited by 16 publications

(9 citation statements)

References 82 publications

(79 reference statements)

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“…Another DLA with [C/ Fe] = +0.59, [Fe/H] = −2.84 at z = 3.07 has been reported by Cooke et al (2012), which is, however, below the limit value of [C/Fe] = +0.7. Two recent works (Welsh et al 2019(Welsh et al , 2022 presenting a collection of all the very metal-poor DLAs in the literature confirm the absence of carbon-enhancement claims.…”

Section: Introductionmentioning

confidence: 75%

Evidence of First Stars-enriched Gas in High-redshift Absorbers*

Saccardi

Salvadori

D’Odorico

et al. 2023

ApJ

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The first stars were born from chemically pristine gas. They were likely massive, and thus they rapidly exploded as supernovae, enriching the surrounding gas with the first heavy elements. In the Local Group, the chemical signatures of the first stellar population were identified among low-mass, long-lived, very metal-poor ([Fe/H] < −2) stars, characterized by high abundances of carbon over iron ([C/Fe] > +0.7): the so-called carbon-enhanced metal-poor stars. Conversely, a similar carbon excess caused by first-star pollution was not found in dense neutral gas traced by absorption systems at different cosmic time. Here we present the detection of 14 very metal-poor, optically thick absorbers at redshift z ∼ 3–4. Among these, 3 are carbon-enhanced and reveal an overabundance with respect to Fe of all the analyzed chemical elements (O, Mg, Al, and Si). Their relative abundances show a distribution with respect to [Fe/H] that is in very good agreement with those observed in nearby very metal-poor stars. All the tests we performed support the idea that these C-rich absorbers preserve the chemical yields of the first stars. Our new findings suggest that the first-star signatures can survive in optically thick but relatively diffuse absorbers, which are not sufficiently dense to sustain star formation and hence are not dominated by the chemical products of normal stars.

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Section: Introductionmentioning

confidence: 75%

Evidence of First Stars-enriched Gas in High-redshift Absorbers*

Saccardi

Salvadori

D’Odorico

et al. 2023

ApJ

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“…Present and future observations will be key to complement highresolution simulations of PopIII star formation (Hirano et al 2015;Stacy et al 2016;Park et al 2021) and specific models for PopIII stars (Schaerer 2002;Raiter et al 2010;Gessey-Jones et al 2022;Larkin et al 2023), to put tighter constraints on their IMF. JWST and ALMA will investigate spectral signatures of PopIII-dominated galaxies (Yajima & Khochfar 2017;Woods et al 2021;Nakajima & Maiolino 2022;Latif et al 2022b), while precise metal abundances measurements in Damped Lyman-𝛼 systems (Welsh et al 2019(Welsh et al , 2022 model the chemical enrichment from PopIII supernovae and stellar archaeology is already constraining the IMF low-mass end with local observations of extremely-metal-poor stars (Frebel et al 2007;Rossi et al 2021;Hartwig et al 2015aHartwig et al , 2022. This will help reducing the uncertainties in the LWB modelling presented here.…”

Section: Summary and Discussionmentioning

confidence: 96%

Modelling the cosmological Lyman-Werner background radiation field in the Early Universe

Incatasciato¹,

Khochfar²,

Oñorbe³

2023

Preprint

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The Lyman-Werner (LW) radiation field is a key ingredient in the chemo-thermal evolution of gas in the Early Universe, as it dissociates H 2 molecules, the primary cooling channel in an environment devoid of metals and dust. Despite its important role, it is still not implemented in cosmological simulations on a regular basis, in contrast to the general UV background. This is in part due to uncertainty in the source modelling, their spectra and abundance, as well as the detailed physics involved in the propagation of the photons and their interactions with the molecules. To overcome these difficulties, we present here a model (with the relative fit) for the mean LW intensity during the first billion years after the Big Bang, obtained by post-processing the high-resolution FiBY simulations with an approximated radiative transfer method that employs accurate cross sections for H 2 , as well as for Hand H + 2 , the chemical species associated with its formation. Absorption by neutral Hydrogen in the IGM and various spectral models for Population III and Population II stars are also included. Our model can be easily applied to other simulations or semi-analytical models as an external homogeneous source of radiation that regulates the star formation in low-mass halos at high-z. We also show how to account for spatial inhomogeneities in the LW radiation field, originating from massive star-forming galaxies that dominate the photon budget up to distances of ∼ 100 proper kpc. Such inhomogeneities have a strong impact on the H 2 abundance and the feasibility of scenarios such as the formation of Direct Collapse Black Holes (DCBHs).

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“…In addition, if the supernova explosion energy is sufficiently large, the yield gas can escape the gravitational binding of the parent halos. Such metals are ejected into the intergalactic medium (Jaacks et al 2018;Liu & Bromm 2020b;Kirihara et al 2020) and leave some impact on the metal abundance pattern of the QSO absorption line systems (Cooke et al 2011;Welsh et al 2022).…”

Section: Stellar Rotationmentioning

confidence: 99%

Merger Conditions of Population III Protostar Binaries

Kirihara

Susa

Hosokawa

et al. 2023

ApJ

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Massive close binary stars with extremely small separations have been observed, and they are possible progenitors of gravitational-wave sources. The evolution of massive binaries in the protostellar accretion stage is key to understanding their formation process. We, therefore, investigate how close the protostars, consisting of a high-density core and a vast low-density envelope, can approach each other but not coalesce. To investigate the coalescence conditions, we conduct smoothed particle hydrodynamics simulations following the evolution of equal-mass binaries with different initial separations. Since Population (Pop) I and III protostars have similar interior structures, we adopt a specific Pop III model with the mass and radius of 7.75 M ⊙ and 61.1 R ⊙ obtained by the stellar evolution calculations. Our results show that the binary separation decreases due to the transport of the orbital angular momentum to spin angular momentum. If the initial separation is less than about 80% of the sum of the protostellar radius, the binary coalesces in a time shorter than the tidal lock timescale. The mass loss up to the merging is ≲3%. After coalescence, the star rotates rapidly, and its interior structure is independent of the initial separation. We conclude that there must be some orbital shrinking mechanism after the protostars contract to enter the zero-age main-sequence stage.

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Oxygen-enhanced Extremely Metal-poor Damped Lyα Systems: A Signpost of the First Stars?

Cited by 16 publications

References 82 publications

Evidence of First Stars-enriched Gas in High-redshift Absorbers*

Evidence of First Stars-enriched Gas in High-redshift Absorbers*

Modelling the cosmological Lyman-Werner background radiation field in the Early Universe

Merger Conditions of Population III Protostar Binaries

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