Kavli Affiliate: George Efstathiou
| First 5 Authors: Joel Wasserman, Joel Wasserman, , ,
| Summary:
The first stars, the chemically pristine Population III, likely played an
important role in heating the intergalactic medium during the epoch of cosmic
dawn. The very high effective temperatures ($sim 10^5$ K) predicted for the
most massive Population III stars could also give rise to tell-tale signatures
in the emission-line spectra of early star clusters or small galaxies dominated
by such stars. Important quantities in modelling their observational signatures
include their photon production rates at ultraviolet energies at which photons
are able to ionize hydrogen and helium, dissociate molecular hydrogen and cause
Lyman-$alpha$ heating. Here, we model the spectral energy distributions of
Population III stars to explore how these key quantities are affected by the
initial mass and rotation of Population III stars given a wide range of models
for the evolution of these stars. Our results indicate that rotating Population
III stars that evolve to effective temperatures $sim 2times 10^5$ K could
potentially give rise to a very strong HeII 1640 emission line in the spectra
from primordial star clusters, without requiring stellar masses of $gtrsim
100 mathrmM_odot$ indicated by previous models for non-rotating Population
III stars. At the same time, the observable impact on 21-cm signatures from
cosmic dawn and epoch of reionization from our set of rotating stars that
evolve to $sim 2times 10^5$ K are modest, and produce potentially detectable
features in the global 21-cm signal and 21-cm power spectrum for high
Population III star formation efficiencies only.
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