The first stars in the universe as Dark Matter laboratories

The first stars in the universe, soon to be observed with the James Webb Space Telescope, are very powerful Dark Matter probes.

If Dark Matter doesn't play a significant role in their formation, then hydrogen burning (Pop~III) stars are believed to form in low multiplicity in high redshift (z~20) micro dark matter halos. We show that the mere observation of a single Pop~III star can be used to place tight constraints on the strength of the interaction between dark matter and regular, baryonic matter. We apply this technique to a candidate Pop~III stellar complex discovered with the Hubble Space Telescope at z~7 and find some of the deepest projected bounds to-date for both spin-dependent and spin-independent DM-nucleon interactions, over a large swath of DM particle masses. Additionally, we show that the most massive Pop~III stars could be used to bypass the main limitations of direct detection experiments: the neutrino background to which they will be soon sensitive. Therefore the method we propose has the potential to probe below the so called “neutrino fog” that will render direct detection experiments very challenging or even downright impossible in the near future.

Conversely, under special conditions first identified by Spolyar et. al (PRL 100, 051101), Dark Matter (DM) can play a significant role in the formation of some of the first stars. When that happens DM burners, i.e. Dark Stars are born. At most one such object forms per micro DM halo, at redshifts as high as 20 and potentially as low as 10. Dark Stars can grow to become supermassive, i.e. SMDSs. Once the DM fuel runs out supermassive dark stars (SMDS) inescapably collapse to supermassive black holes (SMBHs). If discovered with JWST, supermassive dark stars could solve one of the most intriguing puzzles of high energy astrophysics: the origin of the supermassive black holes powering extremely bright quasars at redshifts as high as seven, or even larger. Moreover, early data from JWST seems to indicate that too many very massive, yet compact, galaxies form too early in the universe. This is in stark contrast to most numerical simulations of the formation and assembly of the first galaxies. If some of those high redshift (z>12) galaxy candidates are actually supermassive dark stars, this tension is significantly alleviated. Lastly, the observation of those exotic, dark matter powered, stars would constitute indirect evidence for the DM particle and could, in principle, be used to extract two of its fundamental properties, the particle mass and its annihilation cross section.