The observational signatures of high-redshift dark stars

TL;DR

This paper explores the potential for detecting high-redshift dark stars, which are formed from dark matter annihilation, using current and future telescopes, highlighting the importance of gravitational lensing and the stars' properties.

Contribution

It provides new estimates of the detectability of dark stars at high redshift, considering their mass, temperature, and gravitational lensing effects, and discusses their observational signatures.

Findings

Dark stars below ~1,000 solar masses are too faint for JWST without lensing.

Massive dark stars (~10^7 solar masses) could be detectable with current telescopes at z=10.

Hot dark stars (>30,000 K) may produce bright HII regions, enhancing their observability.

Abstract

The annihilation of dark matter particles in the centers of minihalos may lead to the formation of so-called dark stars, which are cooler, larger, more massive and potentially more long-lived than conventional population III stars. Here, we investigate the prospects of detecting high-redshift dark stars with both existing and upcoming telescopes. We find that individual dark stars with masses below ~1e3 Msolar are intrinsically too faint even for the upcoming James Webb Space Telescope (JWST). However, by exploiting foreground galaxy clusters as gravitational telescopes, certain varieties of such dark stars should be within reach of the JWST at z=10. If more massive dark stars are able to form, they may be detectable by JWST even in the absence of lensing. In fact, some of the supermassive (~1e7 Msolar) dark stars recently proposed are sufficiently bright at z=10 to be detectable even with existing facilities, like the Hubble Space Telescope and 8-10 m telescopes on the ground. Finally, we argue that since the hottest dark stars (Teff > 30000 K) can produce their own HII regions, they may be substantially brighter than what estimates based on stellar atmosphere spectra would suggest.