Day 1279

Wednesday.


1706.08738
Shot noise and biased tracers: a new look at the halo model
Ginzburg, Desjacques, Chan

Shot noise is an important ingredient to any measurement or theoretical modeling of discrete tracers of the LSS.  Recent work has shown that the shot noise in the halo power spectrum becomes increasingly sub-Poissonian at high mass.  While the halo model predicts a shot noise PS in qualitative agreement with the data, it leads to an unphysical white noise in the cross halo-matter and matter PS.  In this work, show that absorbing all the halo model sources of shot noise into the halo fluctuation field leads to meaningful predictions for the shot noise contributions to halo clustering statistics and remove the unphysical white noise from the cross halo-matter statistics.  The prescription straightforwardly maps onto the general bias expansion, so that the renormalized shot noise terms can be expressed as combinations of the halo model shot noises.  Furthermore, demonstrate that non-Poissonian contributions are related to volume integrals over correlation functions and their response to long-wavelength density perturbations.  This leads to a new class of consistency relations for discrete tracers, which appear to be satisfied by the reformulation of the halo model.  Test the theoretical predictions against measurements of halo shot noise bispectra extracted from a large suite of numerical sims.  The model reproduces qualitatively the observed sub-Poissonian noise, although it underestimates the magnitude of this effect.


1706.08860
Intrinsic alignments and splash back radius of dark matter halos from cosmic density and velocity fields
Okumura, Nishimichi, Umetsu, Osato

Investigate the effects of IA of DM halo shapes on cosmic density and velocity fields from cluster to cosmic scales beyond 100 Mpc/h.  Besides the density correlation function binned by he halo orientation angle which was used in the literature, introduce the corresponding two velocity statistics, the angle-binned parities infall momentum and momentum correlation function.  Using large-volume, high-resolution N-body sims, measure the alignment statistics of density and velocity, both in real and redshift space.  Find that the alignment signal is not amplified by z-space distortions at linear scales.  Behaviours of IA in the velocity statistics are similar to those in the density statistics, except that the halo orientations are aligned with the velocity field up to a scale larger than those with the density field, x>100 Mpc/h.  On halo scales, x~R_200m ~ 1 Mpc/h, detect a short steepening in the momentum correlation associated with the physical halo boundary, or the splash back feature, which is found more prominent than in the density correlation.  The results indicate that observations of IA with the velocity field can provide additional information on cosmological models form large scales and on physical sizes of halos from small scales.