Formation of First Galaxies inside Density Peaks and Voids under the Influence of Dark Matter-Baryon Streaming Velocity, I: Initial Condition and Simulation Scheme

Jul 11, 2018
13 pages
Published in:
  • Astrophys.J. 869 (2018) 1, 76
  • Published: Dec 13, 2018
e-Print:

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Abstract: (IOP)
We present a systematic study of the cosmic variance that existed in the formation of the first stars and galaxies. We focus on the cosmic variance induced by the large-scale density and velocity environment engraved at the epoch of recombination. The density environment is predominantly determined by the dark-matter overdensity, and the velocity environment by the dark matter–baryon streaming velocity. Toward this end, we introduce a new cosmological initial condition generator, BCCOMICS, which solves the quasi-linear evolution of small-scale perturbations in the large-scale density and streaming-velocity environment and generates the initial condition for dark matter and baryons, as either particles or grid data at a specific redshift. We also describe a scheme to simulate the formation of the first galaxies inside density peaks and voids, where a local environment is treated as a separate universe. The resulting cosmic variance in the number density of minihalos and the amount of cooling mass are presented as an application. Density peaks become a site for enhanced formation of the first galaxies, which compete with the negative effect from the dark matter–baryon streaming velocity on structure formation.
Note:
  • in press for publication in ApJ; 16 pages, 7 figures, 1 table; BCCOMICS repository specified
  • cosmology: theory
  • dark ages, reionization, first stars
  • Galaxy: formation