The implications of dust for high-redshift protogalaxies and the formation of binary disks

Abstract

Numerical simulations suggest that the first galaxies are formed in protogalactic halos with virial temperatures >= 10^4 K. It is likely that such halos are polluted with trace amounts of metals produced by the first generation of stars. The presence of dust can significantly change the chemistry and dynamics of early galaxies. In this article, we aim to assess the role of dust on the thermal and dynamical evolution of the first galaxies in the presence of a background UV flux, and its implications for the observability of Lyman alpha emitters and sub-mm sources. We have performed high resolution cosmological simulations using the adaptive mesh refinement code FLASH to accomplish this goal. We have developed a chemical network appropriate for these conditions and coupled it with the FLASH code. The main ingredients of our chemical model include the formation of molecules, a multi-level treatment of atomic hydrogen, line trapping of Lyman alpha photons and, photoionization and photodissociation processes in a UV background. We found that the formation of molecules (H_{2} and HD) is significantly enhanced in the presence of dust grains. The presence of a background UV flux strongly influences the formation of molecules by photodissociating them. We explore the evolution after a major merger, leading to the formation of a binary disk. These disks have gas masses of ~10^{7} M_sun at a redshift of 5.4. Each disk lies in a separate subhalo as a result of the merger event. The disks are supported by turbulent pressure due to the highly supersonic turbulence present in the halo. The presence of dust does not significantly reduce the Lyman alpha emission. The emission of Lyman alpha is extended and originates from the envelope of the halo due to line trapping effects. We also find that dust masses of 10^8 M_sun are required to observe the dust continuum emission from z 5 galaxies with ALMA.

12 pages, 10 figures, Accepted for publication in Astronomy and Astrophysics

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Cited by in corpus (16)

• Formation of supermassive black hole seeds
• The Small-Scale Dynamo and Non-Ideal MHD in Primordial Star Formation
• Direct formation of supermassive black holes in metal-enriched gas at the heart of high-redshift galaxy mergers
• A UV flux constraint on the formation of direct collapse black holes
• Magnetic field amplification during gravitational collapse - Influence of initial conditions on dynamo evolution and saturation
• Numerical resolution effects on simulations of massive black hole seeds
• High resolution studies of massive primordial haloes
• Star Formation in the First Galaxies - II: Clustered Star Formation and the Influence of Metal Line Cooling
• The formation of massive Pop III stars in the presence of turbulence
• Large-Scale Structure Formation: from the first non-linear objects to massive galaxy clusters
• Impact of dust cooling on direct collapse black hole formation
• The formation of massive primordial stars in the presence of moderate UV backgrounds
• Low-metallicity star formation: Relative impact of metals and magnetic fields
• Interplay of gas and ice during cloud evolution
• The impact of thermodynamics on gravitational collapse: filament formation and magnetic field amplification
• Impact of an accurate modeling of primordial chemistry in high resolution studies