Evolution of virial clouds-I: from surface of last scattering up to the formation of population-III stars

AbstractThe analysis of WMAP and Planck CMB data has shown the presence of temperature asymmetries towards the halos of several galaxies, which is probably due to the rotation of clouds present in these halos about the rotational axis of the galaxies. It had been proposed that these are hydrogen clouds that should be in equilibrium with the CMB. However, standard theory did not allow equilibrium of such clouds at the very low CMB temperature, but it was recently shown that the equilibrium could be stable. This still does not prove that the cloud concentration and that the observed temperature asymmetry is due to clouds in equilibrium with the CMB. To investigate the matter further, it would be necessary to trace the evolution of such clouds, which we call “virial clouds”, from their formation epoch to the present, so as to confront the model with the observational data. The task is to be done in two steps: (1) from the cloud formation before the formation of first generation of stars; (2) from that time to the present. In this paper we deal with the first step leaving the second one to a subsequent analysis.

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The stochastic enrichment of Population II stars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3342 ◽

2020 ◽

Vol 500 (4) ◽

pp. 5214-5228

Author(s):

Louise Welsh ◽

Ryan Cooke ◽

Michele Fumagalli

Keyword(s):

First Generation ◽

Milky Way ◽

Systematic Errors ◽

Chemical Abundances ◽

Chemical Enrichment ◽

Halo Stars ◽

Chemical Products ◽

Population Iii Stars ◽

Intrinsic Scatter ◽

Population Iii

ABSTRACT We investigate the intrinsic scatter in the chemical abundances of a sample of metal-poor ([Fe/H] < −2.5) Milky Way halo stars. We draw our sample from four historic surveys and focus our attention on the stellar Mg, Ca, Ni, and Fe abundances. Using these elements, we investigate the chemical enrichment of these metal-poor stars using a model of stochastic chemical enrichment. Assuming that these stars have been enriched by the first generation of massive metal-free stars, we consider the mass distribution of the enriching population alongside the stellar mixing and explosion energy of their supernovae. For our choice of stellar yields, our model suggests that the most metal-poor stars were enriched, on average, by $\hat{N}_{\star }=5^{+13}_{-3}~(1\sigma)$ Population III stars. This is comparable to the number of enriching stars inferred for the most metal-poor DLAs. Our analysis therefore suggests that some of the lowest mass structures at z ∼ 3 contain the chemical products from < 13(2σ) Population III enriched minihaloes. The inferred IMF is consistent with that of a Salpeter distribution and there is a preference towards ejecta from minimally mixed hypernovae. However, the estimated enrichment model is sensitive to small changes in the stellar sample. An offset of ∼ 0.1 dex in the [Mg/Ca] abundance is shown to be sensitive to the inferred number of enriching stars. We suggest that this method has the potential to constrain the multiplicity of the first generation of stars, but this will require: (1) a stellar sample whose systematic errors are well understood; and, (2) documented uncertainties associated with nucleosynthetic yields.

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Does the structure of Population III supernova ejecta affect the elemental abundance of extremely metal-poor stars?

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2340 ◽

2020 ◽

Vol 498 (2) ◽

pp. 2676-2687

Author(s):

Gen Chiaki ◽

Nozomu Tominaga

Keyword(s):

First Generation ◽

Abundance Ratio ◽

Mass Scale ◽

Elemental Abundance ◽

Abundance Pattern ◽

Normal Core ◽

Structure Of Population ◽

Population Iii Stars ◽

The One ◽

Population Iii

ABSTRACT The first generation of metal-free (Population III) stars are crucial for the production of heavy elements in the earliest phase of structure formation. Their mass scale can be derived from the elemental abundance pattern of extremely metal-poor (EMP) stars, which are assumed to inherit the abundances of uniformly mixed supernova (SN) ejecta. If the expanding ejecta maintains its initial stratified structure, the elemental abundance pattern of EMP stars might be different from that from uniform ejecta. In this work, we perform numerical simulations of the metal enrichment from stratified ejecta for normal core-collapse SNe (CCSNe) with a progenitor mass $25 \ {\rm M_{\bigodot }}$ and explosion energies 0.7–10 B ($1 \ {\rm B} = 10^{51} \ \rm erg$). We find that SN shells fall back into the central minihalo in all models. In the recollapsing clouds, the abundance ratio [M/Fe] for stratified ejecta is different from the one for uniform ejecta only within ±0.4 dex for any element M. We also find that, for the largest explosion energy (10 B), a neighbouring halo is also enriched. Only the outer layers containing Ca or lighter elements reach the halo, where [C/Fe] = 1.49. This means that C-enhanced metal-poor stars can form from the CCSN even with an average abundance ratio [C/Fe] = −0.65.

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The search for Population III stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308024605 ◽

2008 ◽

Vol 4 (S255) ◽

pp. 75-78 ◽

Cited By ~ 2

Author(s):

Sperello di Serego Alighieri ◽

Jaron Kurk ◽

Benedetta Ciardi ◽

Andrea Cimatti ◽

Emanuele Daddi ◽

...

Keyword(s):

First Generation ◽

Dwarf Galaxy ◽

Big Bang ◽

Metal Enrichment ◽

Promising Candidate ◽

Population Iii Stars ◽

The Universe ◽

Population Iii

AbstractPopulation III stars, the first generation of stars formed from primordial Big Bang material with a top–heavy IMF, should contribute substantially to the Universe reionization and they are crucial for understanding the early metal enrichment of galaxies. Therefore it is very important that these objects, foreseen by theories, are detected by observations. However PopIII stars, searched through the HeII 1640Å line signature, have remained elusive. We report about the search for the HeII line in a galaxy at z = 6.5, which is a very promising candidate. Unfortunately we are not yet able to show the results of this search. However we call attention to the possible detection of PopIII stars in a lensed HII dwarf galaxy at z = 3.4, which appeared in the literature some years ago, but has been overlooked.

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