1604.03109
Characterizing strong lensing galaxy clusters using the Millennium-XXL and MOKA simulations
Giocoli, et al
Investigate the SL statistics in galaxy clusters. Extract DM haloes from Millennium sims, compute their Einstein radius distribution, and find a very good agreement with MC predictions produced with the MOKA code. The distribution of the Einstein radii is well described by a log-normal distribution, with a considerable fraction of the largest systems boosted by different projection effects. Discuss the importance of substructures and triaxiality in shaping the size of the critical lines for cluster size haloes. Then model and interpret the different deviations, accounting for the presence of a BCG and 2 different stellar mass density profiles. Present scaling relations between WL quantities and the size of the Einstein radii. Finally, discuss how sensible is the distribution of the Einstein radii on parameters Omega_m-sigma8 finding that cosmologies with higher Omegam and sigma8 possess a large sample of SL clusters. The Einstein radius distribution may help distinguish Planck13 and WMAP7 cosmology at 3 sigma.
1604.03131
Earth-mass haloes and the emergence of NFW density profiles
Angulo. Hahn, Ludlow, Bronoli
Report sim results from neutralino DM haloes: follow from their emergence at 1 earth mass to a final mass of a few percent solar. Show that the density profiles of the first haloes are well described by a ~r^-1.5 power-law. As haloes grow in mass, their density profiles evolve significantly. In the central regions, they become shallower and reach on average ~r^-1, the asymptotic form of an NFW profile. However, the profile of individual haloes can show non-monotonic density slopes, and be shallower than -1 in some cases. Investigate the transformation of cusp power-law profiles using a series of non-cosmos sims of equal-mass mergers. Contrary to previous findings, observe that temporal variations in the gravitational potential caused by mergers lead to a shallowing of the inner profiles, an effect which is stronger for shallower initial profiles and for mergers that involve a higher number of systems. Depending on the merger details, the resulting profiles can be shallower or steeper than NFW in their inner regions. Mergers have a much weaker effect when the initial profile is given by a broken power-law with an inner slope of -1 (such as NFW or Hernquist profiles). This offers a plausible explanation for the emergence of NFW-like profiles in neutralino DM sims. After their initial collapse, neutrialino DM haloes suffer copious major mergers, which progressively shallows the profile. However, once an NFW-like profile is established, it appears stable against subsequent merging. This suggests that halo profiles are not universal but rather a combination of (1) the physics of the formation of the micro haloes and (2) their early merger history, which are both set by the properties of the DM particle, as well as (3) the resilience of NFW-like profiles to perturbations.
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