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The First Stars and Galaxies: Challenges for the Next Decade Participants
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Talk
Title: Observational Signatures of the First Galaxies Author(s): Jarrett Johnson Abstract: Detection of the radiation emitted from the first galaxies will be made possible in the next decade, with the launch of the James Webb Space Telescope (JWST). A significant fraction of these galaxies may host Population (Pop) III star clusters. The detection of the recombination radiation emitted by such clusters would provide an important new constraint on the initial mass function (IMF) of primordial stars. I will review the expected recombination line signature of Pop III stars, and present the results of cosmological radiation hydrodynamics simulations of the initial stages of Pop III starbursts in a dwarf galaxy at z = 12, from which the time-dependent luminosities and equivalent widths of IMF-sensitive recombination lines are calculated. Owing to the strong dynamical response of the gas to photoheating by massive stars, there is likely a limit on the luminosity of these recombination lines, and it may therefore be unfeasible to detect the emission from Pop III star clusters in the first galaxies at z > 10, even with next generation telescopes. However, Pop III star clusters which form at lower redshifts (i.e. at z < 6) may be detectable in deep surveys by the JWST. I will describe how such clusters could form, present estimates of their abundance and detectability, and discuss the current observational constraints derived from searches for the Pop III recombination line signature in deep surveys.
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