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We present cosmological hydrodynamical simulations including atomic and molecular non-equilibrium chemistry, multi-frequency radiative transfer (0.7–100 eV sampled over 150 frequency bins) and stellar population evolution to investigate the host candidates of the seeds of supermassive black holes coming from direct collapse of gas in primordial haloes direct-collapse black holes, DCBHs. We consistently address the role played by atomic and molecular cooling, stellar radiation and metal spreading of C, N, O, Ne, Mg, Si, S, Ca, Fe, etc. from primordial sources, as well as their implications for nearby quiescent proto-galaxies under different assumptions for early source emissivity, initial mass function, and metal yields. We find that putative DCBH (direct-collapse black holes) host candidates need powerful primordial stellar generations, since common solar-like stars and hot OB-type stars are neither able to determine the conditions for direct collapse nor capable of building up a dissociating Lyman–Werner background radiation field. Thermal and molecular features of the identified DCBH host candidates in the scenario with very massive primordial stars seem favourable, with illuminating Lyman–Werner intensities featuring values of 1 – 50J21. Nevertheless, additional nonlinear processes, such as merger events, substructure formation, rotational motions, and photo-evaporation, should inhibit pure direct-collapse black hole formation in two-third of the cases. Local turbulence may delay gas direct collapse almost irrespectively from other environmental conditions. The impact of large Lyman–Werner fluxes at distances smaller than ~5 kpc is severely limited by metal pollution.
The period 2009-2011 has seen a consolidation of our theoretical understanding around the Flat-Λ CDM Universe model, with experiments on several fronts providing observations consistent with this model, and leading to improved constraints on the values of H0, ΩB, ΩM, and ΩΛ. The recently launched Planck Satellite has started to provide a wealth of new observations of the Cosmic Microwave Background (CMB) and should lead to substantial progress in the physics of the CMB over the coming years. There has also be a steady progress in mapping the formation of structure and galaxies to higher and higher redshifts. Observations of objects at the highest redshifts are suggestive that the reionization of the Universe might not be complete at these epochs. This epoch will be probed in the near future with low-frequency radio surveys. This report, prepared from the inputs received from the committee members, concentrates on these areas.
Population 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.
With the advent in the near future of radio telescopes such as LOFAR and the SKA, a new window on the high-redshift Universe will be opened. In particular, it will be possible, for the first time, to observe the 21-cm signal from the diffuse IGM prior to its complete re-ionization and thus probe the ‘dark ages’. I discuss the theoretical modelling of the re-ionization process and its observability through the 21-cm signal and the CMB anisotropies.
We will present simulations of the IGM reionization process and discuss its observability through the 21 cm line. We find that the primordial stellar sources considered in this study give a value of the reionization epoch and of the electron optical depth consistent with the observations by WMAP, without invoking the presence of additional sources of ionization. Depending on the redshift of reionization, broad-beam observations at frequencies < 100–150 MHz with the next generation of radio telescopes should reveal angular fluctuations in the sky brightness temperature in the range 5 —20 mK on scales < 5 arcmin.
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