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Abstract
Using cosmological dark matter (DM) only simulations of a (1.6 Gpc/h)3
volume from the Legacy simulation project, we calculate Cosmic Mach
Numbers (CMN) and perform a theoretical investigation of their relation
with halo properties and features of the density field to gauge their
use as an measure of the environment. CMNs calculated on individual
spheres show correlations with both the overdensity in a region and the
density gradient in the direction of the bulk flow around that region.
To reduce the scatter around the median of these correlations, we
introduce a new measure, the rank ordered Cosmic Mach number (M^g), which shows a tight correlations with the overdensity δ=ρ−ρ¯ρ¯.
Measures of the large-scale density gradient as well as other average
properties of the halo population in a region show tight correlations
with M^g as well. Our results in this first empirical study suggest that M^g
is an excellent proxy for the underlying density field and hence
environment that can circumvent reliance on number density counts in a
region. For scales between 10 and 100Mpch−1, Mach numbers calculated using DM haloes (> 1012 M⊙)
that would typically host massive galaxies are consistent with
theoretical predictions of the linear matter power spectrum at a level
of 10 percent due to non-linear effects of gravity. At redshifts z
≥ 3, these deviations disappear. We also quantify errors due to missing
large-scale modes in simulations. Simulations of box size ≤1 Gpc h−1 typically predict CMNs 10–30 per cent too small on scales of ∼100 Mpc h−1.
Original language | English |
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Pages (from-to) | 27-40 |
Number of pages | 14 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 512 |
Issue number | 1 |
Early online date | 25 Feb 2022 |
DOIs | |
Publication status | Published - 1 May 2022 |
Keywords / Materials (for Non-textual outputs)
- astro-ph.CO
- Software: simulations
- large-scale structure of Universe
- dark matter
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