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Paper: The First Galaxies: Signatures of the Initial Starburst
Volume: 419, Galaxy Evolution: Emerging Insights and Future Challenges
Page: 335
Authors: Johnson, J. L.; Greif, T. H.; Bromm, V.; Klessen, R. S.; Ippolito, J.
Abstract: To study the properties of the radiation the first galaxies at z ≥ 10, as they depend on the dynamical evolution of the galaxies, we carry out cosmological radiation hydrodynamics simulations of Population III (Pop III) starbursts in a dwarf galaxy at z∼12.5. For different assumptions for the star formation efficiency of the galaxy and for the stellar initial mass function (IMF), we calculate the luminosities and equivalent widths (EWs) of Hα, Lyα, and He II λ1640. We find that photoheating by massive stars causes a strong dynamical response of the gas, which contributes to a weak correlation between luminosity emitted in hydrogen recombination lines and the total mass in stars; however, owing to the low escape fraction of He II-ionizing photons, the luminosity emitted in He II λ1640 is much more strongly correlated with the total stellar mass. The ratio of the luminosities in Lyα and Hα to He II λ1640 is found to be an indicator of the IMF in many cases. The EW of the He II λ1640 emission line is relatively insensitive to dynamical effects, making it an especially reliable indicator of IMF.
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