1702.04348
Mapping substructure in the HST Frontier Fields cluster lenses and in cosmological simulations
Natarajan, et al
Map the lensing-inferred substructure in the first 3 clusters observed by HST Frontier Fields Initiative (HSTFF): Abell 2744 (z=0.308), MACSJ0416 (z=0.396) and MACSJ1149 (z=0.543). Statistically resolving DM sub haloes down to ~1e9.5 Msun, compare the derived subhalo mass functions (SHMFs) to theoretical predictions from analytical models and with numerical sims in a LCDM cosmology. Mimicking the observational cluster member selection criteria in the HSTFF, report excellent agreement in both amplitude and shape of the SHMF over 4 decades in subhalo mass (1e9-13 Msun). Projection effects do not appear to introduce significant errors in the determination of SHMFs from simulations. Do not find evidence for substructure crisis, analogous to the missing satellite problem in the Local Group, on cluster scales, but rather excellent agreement of the count-matched HSTFF SHMF down to M_{sub halo}/M_{halo}~1e-5. However, do find discrepancies in the radial distribution of sub haloes inferred from HSTFF cluster lenses compared to determinations from simulated clusters. This suggests that although the selected simulated clusters match the HSTFF sample in mass, they do not adequately capture the dynamical properties and complex merging morphologies of these observed cluster lenses. Therefore, HSTFF clusters are likely observed in a transient evolutionary stage that is presently insufficiently sampled in cosmo sims. The abundance and mass function of DM substructure in cluster lenses continues to offer an important test of the LCDM paradigm, and at present find no tension between model predictions and observations.
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