Dark matter and cosmic structure

Abstract

The current standard model for the evolution of cosmic structure is reviewed, tracing its development over the last forty years and focussing specifically on the role played by numerical simulations and on aspects related to the nature of dark matter. PreambleThe development of a standard model of cosmological structure formation over the last forty years must count as one of the great success stories in Physics. The model describes the geometry and material content of the Universe, explaining how structure -galaxies of various sizes and types, groups and clusters of galaxies, the entire cosmic web of filaments and voids -emerged from a hot and near-uniform Big Bang. This astonishing richness appears to have grown from quantum zero-point fluctuations produced during a period of cosmic inflation occurring very soon after the beginning of our Universe. Over the subsequent 13.7 billion years, these small density perturbations were amplified by the relentless action of gravitational forces due predominantly to dark matter, but illuminated by complex astrophysical phenomena involving ordinary matter. In the standard model, the dark matter, which makes up five sixths of all matter, is hypothesised to be a weakly interacting non-baryonic elementary particle, created in the early stages of cosmic evolution.In this article we will review the standard model of cosmic structure formation, focusing on the nonlinear processes that transformed the near-uniform universe that emerged from the Big Bang into the highly structured world we observe today. We will highlight the critical role that computer simulations have played in understanding this transformation, emphasizing gravitational phenomena associated with the dark matter, and only rather briefly discussing the crucially important, but more complex, processes that shape the directly observable baryonic components. Rather than presenting a complete and thorough review of the literature, our intention is to provide an account of the main ideas and advances that have shaped the subject. We begin by presenting in Table 1 a chronological listing of the landmark developments that have driven this remarkable story.

The Coevolution of Supermassive Black Holes and Massive Galaxies at High Redshift

“…Since these processes start, major mergers are no longer relevant for the galaxy/QSO evolution and are neglected. This is a crucial feature of our model, as opposed to other treatments (for a list, see Scannapieco et al 2012; for a critical view, see White 2012 andKaviraj et al 2013). …”

Using the Milky Way satellites to study interactions between cold dark matter and radiation

“…However, as the resolution of the simulations improved, significant discrepancies emerged on small scales. For example, DM halo profiles for dwarf galaxies are less cuspy than predicted by CDM (Dubinski & Carlberg 1991) (although this is still under debate, see Frenk & White 2012) and large CDM haloes do not form as many stars as expected (the 'too big to fail problem', Boylan-Kolchin et al 2011). …”

“…Modern evidence now includes the pivotal role of DM in the formation of structure in the Universe (Frenk & White 2012). Although around 80 per cent of the matter content of the Universe is thought to be in the form of DM particles (Ade et al 2013), these are yet to be discovered (Akerib et al 2013).…”

Revealing modified gravity signals in matter and halo hierarchical clustering

“…Here, the theory aspires to describe the growth on tiny irregularities in the course of the cosmic expansion history from initial density perturbations of the order of ∼ 10 −5 , as observed in the CMB [32], to present day DM haloes characterised by central densities of > ∼ 10 6 [see e.g. [33][34][35]. Thus, to connect the theoretical predictions with observations we need an accurate description of the growth of structures spanning more then 10 orders of magnitude in density.…”