Dark Stars: a new look at the First Stars in the Universe (0903.3070v1)

Abstract: We have proposed that the first phase of stellar evolution in the history of the Universe may be Dark Stars (DS), powered by dark matter heating rather than by nuclear fusion, and in this paper we examine the history of these DS. The power source is annihilation of Weakly Interacting Massive Particles (WIMPs) which are their own antiparticles. These WIMPs are the best motivated dark matter (DM) candidates and may be discovered by ongoing direct or indirect detection searches (e.g. FERMI /GLAST) or at the Large Hadron Collider at CERN. A new stellar phase results, powered by DM annihilation as long as there is DM fuel, from millions to billions of years. We build up the dark stars from the time DM heating becomes the dominant power source, accreting more and more matter onto them. We have included many new effects in the current study, including a variety of particle masses and accretion rates, nuclear burning, feedback mechanisms, and possible repopulation of DM density due to capture. Remarkably, we find that in all these cases, we obtain the same result: the first stars are very large, 500-1000 times as massive as the Sun; as well as puffy (radii 1-10 A.U.), bright ($10^6-10^7 L_\odot$), and cool ($T_{surf} < $10,000 K) during the accretion. These results differ markedly from the standard picture in the absence of DM heating. Hence DS should be observationally distinct from standard Pop III stars. In addition, DS avoid the (unobserved) element enrichment produced by the standard first stars. Once the dark matter fuel is exhausted, the DS becomes a heavy main sequence star; these stars eventually collapse to form massive black holes that may provide seeds for the supermassive black holes and intermediate black holes, and explain ARCADE data.

Theoretical Analysis of Early Universe Star Formation through Dark Matter Heating

The paper "Dark Stars: a new look at the First Stars in the Universe" presents a compelling theoretical approach to the early stages of stellar evolution within the universe, proposing the existence of "Dark Stars" (DS) powered by dark matter heating rather than by conventional nuclear fusion processes. This investigation is premised on the role of Weakly Interacting Massive Particles (WIMPs), which serve as viable dark matter candidates and whose annihilation processes potentially fuel these primordial stars. The paper's authors provide numerous computational simulations to underscore the feasibility of Dark Stars in varying cosmological conditions.

Core Findings

The central thesis of the research posits that DS represent a unique, non-nucleosynthetic phase of stellar evolution, markedly divergent from conventional Population III stars. The authors argue that the accretion of baryonic matter onto the DS, coupled with dark matter heating, results in star formations substantially larger, cooler, and brighter than standard models predict. Notably, under the influence of dark matter heating, DS can attain masses between 500-1000 solar masses with radii extending to 1-10 Astronomical Units (AU).

Detailed Numerical Results

Through multiple simulations incorporating varied particle masses, accretion models, and feedback mechanisms, a consistent outcome is evident: DS emerge as genuinely massive stellar entities. The analysis highlights:

• DS temperatures remain below 10,000 Kelvin during the accretion phase, contrasting significantly with the expected temperatures of nuclear-burning stars which exceed 50,000 Kelvin.
• The luminosity of DS is reported between $10^6$-$10^7 L_\odot$, enabled by the energy efficiency of dark matter annihilation.
• Contrary to legacy theories, DS do not contribute to significant stellar nucleosynthesis and element enrichment, suggesting observational differentiation from known stellar forms.

Theoretical Implications

The implications of this paper are multifaceted, suggesting not only observational but also cosmological impacts. Understanding DS contributes to unraveling the early universe's reionization characteristics and provides seed black holes that could evolve into supermassive black holes. This notion offers plausible explanations for high-redshift extragalactic phenomena such as quasars, gamma-ray bursts, and the radio excess detected by ARCADE.

Practical and Future Prospects

The theoretical framework of DS provides observational targets for future generations of telescopes and instruments, like JWST and TMT, especially if such stars exist towards lower redshifts. The differences in luminosity and temperature from typical Population III stars make DS potential markers for understanding primordial cosmology.

Moreover, the dark matter origin presents a novel area for synergy between particle physics and astrophysics. WIMP detection efforts (e.g., those at the Large Hadron Collider) might eventually identify particles responsible for DS heating, offering further evidence for the concept.

Conclusion

In conclusion, this paper adds a provocative layer to our understanding of star formation in the universe's infancy, shifting paradigmas towards the potential prevalence and significance of dark matter-powered entities. The continued exploration into DS and their properties could redefine theoretical astrophysics, underpinning a model where dark matter's role transcends mere gravitational influence to pivotal involvement in star formation processes.