Cosmological Advection Flows in the Presence of Primordial Black Holes as Dark Matter and Formation of First Sources

In the inflation-based cosmology the dark matter (DM) density component starts moving with respect to the universal expansion at z(eq) similar to 3200 while baryons remain frozen until z(rec) similar to 1100. It has been suggested that in this case postlinear corrections to the evolution of small fluctuations would result, for the standard Lambda-dominated cold DM (CDM) model, in delayed formation of early objects as supersonic advection flows develop after recombination, so baryons are not immediately captured by the DM gravity on small scales. We develop the hydrodynamical description of such two-component advection and show that, in the supersonic regime, the advection within irrotational fluids is governed by the gradient of the difference of the kinetic energies of the two (DM and baryonic here) components. We then apply this formalism to the case where DM is made up of LIGO-type black holes (BHs) and show that there the advection process on scales relevant for early structure collapse will differ significantly from the earlier discussed (CDM) case because of the additional granulation component to the density field produced during inflation. The advection here will lead efficiently to the common motion of the DM and baryon components on scales relevant for collapse and formation of first luminous sources. This leads to early collapse, making it easier to explain the existence of supermassive BHs observed in quasars at high z > 7. The resultant net advection rate reaches minimum around less than or similar to 10(9) M-circle dot and subsequently rises to a secondary maximum near the typical mass of similar to 10(12) M-circle dot, which may be an important consideration for formation of galaxies at z less than or similar to (a few).

Automated summary

The study focuses on the effects of advection motion of dark matter and baryons in inflation-based cosmology on early structure formation, suggesting a delayed formation of early objects and efficient common motion of DM and baryon components on scales relevant for collapse and formation of first luminous sources. This leads to an easier explanation for the existence of supermassive black holes observed in quasars at high z > 7.