Speaker
Description
The Lambda Cold Dark Matter paradigm, with a power-law primordial power spectrum, explains successfully the large-scale (>> Mpc) structure of the Universe. However, the small-scale (< Mpc) structures are relatively unconstrained. Recently, JWST has found surprisingly early formation of massive galaxies at high redshifts. Small, dense, dark matter subhaloes have been inferred from strong gravitational lensing. Furthermore, a large number of satellite galaxies have been discovered, larger than expected from standard theoretical models. An enhancement of the small-scale (blue-tilted) primordial power spectrum could be a possible solution to these tensions.
Using cosmological simulations, we investigate how a blue-tilted primordial power spectrum affects cosmic structure formation. We find that in the blue-tilted model, dark matter structures form much earlier, potentially facilitating the early galaxy formation. We also find that blue-tilted halos develop higher central densities, possibly detectable via strong gravitational lensing. With cosmological zoom-in simulations of the Milky Way-mass dark matter halos, we find the subhalo mass function is enhanced by more than a factor of two for subhalo masses below 10^10 solar masses. Finally, we show that the blue tilted model can also produce detectable signatures on 21cm signals around cosmic dawn and reionization.
| Research Area | Cosmology: late universe |
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