Dark stars: Implications and constraints from cosmic reionization and extragalactic background radiation

Abstract

Dark stars powered by dark matter annihilation have been proposed as the first luminous sources in the universe. These stars are believed to form in the central dark matter cusp of low-mass minihalos. Recent calculations indicate stellar masses up to \sim1000 solar masses and/or have very long lifetimes. The UV photons from these objects could therefore contribute significantly to cosmic reionization. Here we show that such dark star models would require a somewhat artificial reionization history, based on a double-reionization phase and a late star-burst near redshift $z\sim 6$, in order to fulfill the WMAP constraint on the optical depth as well as the Gunn-Peterson constraint at $z\sim 6$. This suggests that, if dark stars were common in the early universe, then models are preferred which predict a number of UV photons similar to conventional Pop. III stars. This excludes dark stars with 100 solar masses that enter a main-sequence phase and other models that lead to a strong increase in the number of UV photons. We also derive constraints for massive as well as light dark matter candidates from the observed X-ray, gamma-ray and neutrino background, considering dark matter profiles which have been steepened during the formation of dark stars. This increases the clumping factor at high redshift and gives rise to a higher dark matter annihilation rate in the early universe. We furthermore estimate the potential contribution from the annihilation products in the remnants of dark stars, which may provide a promising path to constrain such models further, but which is currently still uncertain.

16 pages, 9 figures, accepted at PRD

References in corpus (13)

• Dark matter and the first stars: a new phase of stellar evolution
• Early Cosmological HII/HeIII Regions and Their Impact on Second-Generation Star Formation
• Minimal Dark Matter predictions for galactic positrons, anti-protons, photons
• Evidence Of Dark Matter Annihilations In The WMAP Haze
• Neutrino Constraints on the Dark Matter Total Annihilation Cross Section
• The Effects of Dark Matter Decay and Annihilation on the High-Redshift 21 cm Background
• Dark matter annihilation or unresolved astrophysical sources? Anisotropy probe of the origin of cosmic gamma-ray background
• Constraining DM through 21 cm observations
• Conservative Constraints on Dark Matter Annihilation into Gamma Rays
• Reionization - A probe for the stellar population and the physics of the early universe
• Detection of Atmospheric Muon Neutrinos with the IceCube 9-String Detector
• Can Dark Matter Annihilation Dominate the Extragalactic Gamma-Ray Background?
• Cosmic constraints rule out s-wave annihilation of light dark matter

Cited by in corpus (1)

• The prospects of finding the first quasars in the universe