Cosmological simulations of the first galaxies

PhD ceremony: Mr. M.A. Latife, 14.45 uur, Aula Academiegebouw, Broerstraat 5, Groningen

Dissertation: Cosmological simulations of the first galaxies

Promotor(s): prof. S. Zaroubi, prof. M.C. Spaans

Faculty: Mathematics and Natural Sciences

The prime objective of this thesis is to study the formation of the first galaxies. We have performed high resolution cosmological simulations using the code FLASH.

We find that by trapping Lyman alpha photons temperature of the protogalactic halo remains higher or equal to 104 K. Consequently, fragmentation to stellar masses remains inhibited and makes such halos the potential sites for the formation of black holes. We also compared our results with atomic as well as molecular hydrogen cooling halos and found significant differences. We also estimated the emission of Lyman alpha photons from the first galaxies. We find that gas falls into the center of a galaxy through cold streams of gas and results in the emission of Lyman alpha photons. The emission of Lyman alpha photons is extended and Lyman alpha flux of 10−17 erg/s/cm2 is produced which can be detected with upcoming James Webb Space telescope. We also studied the impact of background UV flux on the emission of Lyman alpha radiation from the first galaxies and its implications for the formation of molecules in primordial gas. We find that the presence of a background UV flux enhances the emission of Lyman alpha photons and influences the formation of molecules in the primordial gas. We found that the 21 cm signal that emanates from the cosmic dark ages is very weak in the absence of radiation sources and will be difficult to observe.