The effects of peculiar velocities on the morphological properties of large-scale structure

Abstract

It is known that the large-scale structure (LSS) mapped by a galaxy redshift survey is subject to distortions by the galaxies' peculiar velocities. Besides the signatures generated in common N-point statistics, such as the anisotropy in the galaxy 2-pt correlation function, the peculiar velocities also induce distinct features in LSS's morphological properties, which are fully described by four Minkowski functionals (MFs), i.e., the volume, surface area, mean curvature and Euler characteristic (or genus). In this work, by using large suite of N-body simulations, we present and analyze these important features in the MFs of LSS on both (quasi-)linear and non-linear scales. With a focus on non-linear scale, we identify the features uniquely induced by the fingers-of-God effect that show up only on non-linear scales, especially in the surface-area weighted mean curvature in high density threshold regions. We also find the MFs may give competitive constraints on cosmological parameters compared to the power spectrum. These results are important for cosmological applications of MFs of LSS, and probablly open up a new way to study the peculiar velocity field itself.

Probing massive neutrinos with the Minkowski functionals of large-scale structure

“…In a recent work of ours, we find the MFs for the distribution of dark matter halos are more competitive in constraining f(R) gravity than those for the dark matter density field [44]. Another recent work of ours finds that the MFs of matter distribution measured in redshift space place tighter constraints on cosmological parameters than the redshift-space power spectrum [55]. Both these preliminary findings are encouraging.…”

“…Since V 2 /V 1 is a global measure of the mean curvature of the surfaces of excursion sets, it can be influenced by various changes in the structure. For example, the increase of small voids in number makes V 2 /V 1 smaller while more small islands increase it; when voids and islands grow in size, the absolute value of V 2 /V 1 drops; for a spheroid with two axes of length r and λr, |V 2 /V 1 | is larger when |λ − 1| is larger [55] for fixed r. V 2 /V 1 and the difference in V 2 /V 1 between cosmologies with massive and massless neutrinos are plotted in figure 3, we postpone detailed interpretation of these curves to section 4.4. We note that there is a small sharp turning point in the blue dashed line in the right panel of figure 3, its origin is numerical rather than physical.…”

“…We also present a detailed analysis of the effects of nonzero neutrino mass on LSS's morphology with our more realistic choice for the smoothing scales, compared to [53] which adopted idealistic choices (specifically, ∼0.1 and ∼0.2h −1 Mpc). For this purpose, we propose a new indicator based on the MFs, i.e., the surface-area weighted average of the mean curvature, which is sensitive to the size and shape changes of voids and halos, and has been used in our analysis for the effects of peculiar velocities on LSS in [55].…”