1611.03554
Cross-correlation of weak lensing and gamma rays: implications for the nature of dark matter
Tröster, et al
Measure the cross-correlation between Fermi-LAT gamma-ray photons and over 1000 deg2 of WL data from CFHTLenS, RCSLenS, and KiDS. Present the first measurement of tomographic WL cross-correlations and the first application of spectral binning to cross-correaltions between gamma rays and WL. The measurements are performed using an angular power spectrum estimator while the covariance is estimated using an analytical prescription. Verify the accuracy of the covariance estimate by comparing it to 2 internal covariance estimators. Based on the non-detenction of a cross-correlation signal, derive constraints on weakly interacting massive particle (WIMP) DM. Compute exclusion limits on the DM annihilation cross-section <sigma_ann v>, decay rate Gamma_dec, and particle mass m_DM. Find that in the absence of a cross-correlation signal, tomography does not significantly improve the constraining power of the analysis. Assuming a strong contribution to the gamma-ray flux due to small scale clustering of DM and accounting for known astrophysical sources of gamma rays, exclude the thermal relic cross-section for masses of m_DM<~ 20 GeV.
1611.03619
Excursion set peaks: the role of shear
Castorina, Paranjape, Hahn, Sheth
Recent analytical work on the modelling of DM abundances and clustering has demonstrated the advantages of combining the excursion set approach with peaks theory. Extend these ideas and introduce a model of excursion set peaks that incorporates the role of initial tidal effects or shear in determining the gravitational collapse of dark haloes. The model -- in which the critical density threshold for collapse depends on the tidal influences acting on protohaloes -- is well motivated from ellipsoidal collapse arguments and is also simple enough to be analytically tractable. Show that the predictions of this model are in very good agreement with measurements of the halo mass function and traditional scale dependent halo bias in N-body sims across a wide range of masses and redshift. The presence of shear in the collapse threshold means that halo bias is naturally predicted to be nonlocal, and that protohalo densities at fixed mass are naturally predicted to have Lognormal-like distributions. Present the first direct estimate of Lagrangian nonlocal bias in N-body sims, finding broad agreement with the model predictions. Finally, the simplicity of the model (which has essentially a single free parameter) opens the door to building efficient and accurate non-universal fitting functions of halo abundances and bias for use in precision cosmology.
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