Primordial Black Holes as Generators of Cosmic Structures
Résumé
Primordial black holes (PBHs) could provide the dark matter in various mass windows below 10^2 M_⊙ and those of 30 M_⊙ might explain the LIGO events. PBHs much larger than this might have important consequences even if they provide only a small fraction of the dark matter. In particular, they could generate cosmological structure either individually through the ‘seed’ effect or collectively through the ‘Poisson’ effect, thereby alleviating some problems associated with the standard cold dark matter scenario. If the PBHs all have a similar mass and make a small contribution to the dark matter, then the seed effect dominates on small scales, in which case PBHs could generate the supermassive black holes in galactic nuclei or even galaxies themselves. If they have a similar mass and provide the dark matter, the Poisson effect dominates on all scales and the first bound clouds would form earlier than in the usual scenario, with interesting observational consequences. If the PBHs have an extended mass spectrum, which is more likely, they could fulfill all three roles – providing the dark matter, binding the first bound clouds, and generating galaxies. In this case, the galactic mass function naturally has the observed form, with the galaxy mass being simply related to the black hole mass. The stochastic gravitational wave background from the PBHs in this scenario would extend continuously from the LIGO frequency to the LISA frequency, offering a potential goal for future surveys.
Mots clés
04.70.Bw
97.60.Lf
gravitational waves
stars: Population III
galaxies: formation
quasars: supermassive black holes
dark matter
early Universe
galaxy: mass
black hole: primordial
black hole: mass
gravitational radiation: stochastic
gravitational radiation: background
dark matter: parametrization
structure
Poisson
cloud
LIGO
mass spectrum
nucleus
LISA