Impacts of dark stars on reionization and signatures in the cosmic microwave background

Pat Scott, Aparna Venkatesan, Elinore Roebber, Paolo Gondolo, Elena Pierpaoli, Gil Holder

Research output: Contribution to journalArticlepeer-review

Abstract

We perform a detailed and systematic investigation of the possible impacts of dark stars on the reionization history of the universe, and its signatures in the cosmic microwave background (CMB). We compute hydrogen reionization histories, CMB optical depths, and anisotropy power spectra for a range of stellar populations including dark stars. If dark stars capture large amounts of dark matter (DM) via nuclear scattering, reionization can be substantially delayed, leading to decreases in the integrated optical depth to last scattering and large-scale power in the EE polarization power spectrum. Using the integrated optical depth observed by the Wilkinson Microwave Anistropy Probe seven-year mission, in our canonical reionization model we rule out the section of parameter space where dark stars with high scattering-induced capture rates tie up ≳ 90% of all the first star-forming baryons, and live for ≳ 250Myr. When nuclear scattering delivers only moderate amounts of DM, reionization can instead be sped up slightly, modestly increasing the CMB optical depth. If dark stars do not obtain any DM via nuclear scattering, effects on reionization and the CMB are negligible. The effects of dark stars on reionization and its CMB markers can be largely mimicked or compensated for by changes in the existing parameters of reionization models, making dark stars difficult to disentangle from astrophysical uncertainties, but also widening the range of standard parameters in reionization models that can be made consistent with observations.

Original languageEnglish (US)
Article number129
JournalAstrophysical Journal
Volume742
Issue number2
DOIs
StatePublished - Dec 1 2011
Externally publishedYes

Keywords

  • cosmic background radiation
  • dark ages, reionization, first stars
  • dark matter
  • stars: Population III

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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