scholarly journals Dark Matter Haloes and Subhaloes

Galaxies ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 81 ◽  
Author(s):  
Jesús Zavala ◽  
Carlos S. Frenk
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Background Radiation ◽  
Cosmic Background Radiation ◽  
Mass Range ◽  
Temperature Structure ◽  
N Body Problem ◽  
Central Regions ◽  
Low Mass

The development of methods and algorithms to solve the N-body problem for classical, collisionless, non-relativistic particles has made it possible to follow the growth and evolution of cosmic dark matter structures over most of the universe’s history. In the best-studied case—the cold dark matter or CDM model—the dark matter is assumed to consist of elementary particles that had negligible thermal velocities at early times. Progress over the past three decades has led to a nearly complete description of the assembly, structure, and spatial distribution of dark matter haloes, and their substructure in this model, over almost the entire mass range of astronomical objects. On scales of galaxies and above, predictions from this standard CDM model have been shown to provide a remarkably good match to a wide variety of astronomical data over a large range of epochs, from the temperature structure of the cosmic background radiation to the large-scale distribution of galaxies. The frontier in this field has shifted to the relatively unexplored subgalactic scales, the domain of the central regions of massive haloes, and that of low-mass haloes and subhaloes, where potentially fundamental questions remain. Answering them may require: (i) the effect of known but uncertain baryonic processes (involving gas and stars), and/or (ii) alternative models with new dark matter physics. Here we present a review of the field, focusing on our current understanding of dark matter structure from N-body simulations and on the challenges ahead.

scholarly journals Dragging Force on Galaxies Due to Streaming Dark Matter

1990 ◽  
Vol 124 ◽  
pp. 645-649
Author(s):  
Tetsuya Hara ◽  
Shigeru Miyoshi
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Rest Frame ◽  
Background Radiation ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
The Galaxy ◽  
Microwave Background Radiation ◽  
The Universe

It has been reported that galaxies in large regions (~102Mpc), including some clusters of galaxies, may be streaming coherently with velocities up to 600km/sec or more with respect to the rest frame determined by the microwave background radiation.) On the other hand, it is suggested that the dominant mass component of the universe is dark matter. Because we can only speculate the motion of dark matter from the galaxy motions, much attention should be paid to the correlation of velocities between the observed galaxies and cold dark matter. So we investigate whether such coherent large-scale streaming velocities are due to dark matter or only to baryonic objects which may be formed by piling up of gases due to some explosive events.

scholarly journals Cold Dark Matter: Galactic Halos

1987 ◽  
Vol 117 ◽  
pp. 280-280
Author(s):  
C. S. Frenk
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Galaxy Formation ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Initial Conditions ◽  
Standard Theory ◽  
Galactic Halos ◽  
Rotation Curves ◽  
Central Regions

A flat universe dominated by cold dark matter (CDM) is an attractive arena for the formation of galaxies and large scale structure. Current upper limits on anisotropies of the cosmic microwave background and the standard theory of primordial nucleosynthesis are both compatible with such a universe. Furthermore a flat CDM model in which galaxy formation is biased towards high density regions provides a good match to the observed distribution of galaxies on Megaparsec scales. In collaboration with M. Davis, G. Efstathiou and S.D.M. White, we have carried out a high resolution N-body simulation which shows that this model can also account for the abundance and characteristic properties of galactic halos. The initial conditions for this simulation were based on the results of our previous work which gave both the scaling and overall normalisation of the initial CDM fluctuation spectrum appropriate to the biased galaxy formation model. We simulated a cubic region of present size 14 Mpc (H0 = 50km/s/Mpc) from a redshift of 6 to the present day, with a resolution of 2kpc initially and 14 kpc at the end. We found that by a redshift of 2.5 about 20 clumps with circular speeds exceeding 100 km/s had collapsed near high peaks of the initial linear density field. Between Z = 2.5 and the present most of them remained isolated and accreted extensive outer halos, while others merged into larger systems. The rotation curves of the final smooth systems were impressively flat at large radii resembling the measured rotation curves of spiral galaxies. Furthermore, the abundance of clumps with circular velocities larger than 150 km/s was about the same as the abundance of galaxies brighter than M33 expected in a volume the size of our simulation. Significant transfer of angular momentum to surrounding material occurred as large subclumps merged. Most of this angular momentum was originally invested in the orbital motions of the subclumps. As a result, the central regions of merged objects showed little rotation.

scholarly journals SHARP – VII. New constraints on the dark matter free-streaming properties and substructure abundance from gravitationally lensed quasars

2019 ◽  
Vol 492 (2) ◽  
pp. 3047-3059 ◽  
Author(s):  
J-W Hsueh ◽  
W Enzi ◽  
S Vegetti ◽  
M W Auger ◽  
C D Fassnacht ◽  
...  
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Complex Structure ◽  
Mass Range ◽  
Recent Analysis ◽  
Confidence Limits ◽  
A Value ◽  
Low Mass ◽  
Hydrodynamical Simulations ◽  
First Time

ABSTRACT We present an analysis of seven strongly gravitationally lensed quasars and the corresponding constraints on the properties of dark matter. Our results are derived by modelling the lensed image positions and flux-ratios using a combination of smooth macro-models and a population of low-mass haloes within the mass range of 106–109 M⊙. Our lens models explicitly include higher order complexity in the form of stellar discs and luminous satellites, as well as low-mass haloes located along the observed lines of sight for the first time. Assuming a cold dark matter (CDM) cosmology, we infer an average total mass fraction in substructure of $f_{\rm sub} = 0.012^{+0.007}_{-0.004}$ (68 per cent confidence limits), which is in agreement with the predictions from CDM hydrodynamical simulations to within 1σ. This result is closer to the predictions than those from previous studies that did not include line-of-sight haloes. Under the assumption of a thermal relic dark matter model, we derive a lower limit on the particle relic mass of mth > 5.58 keV (95 per cent confidence limits), which is consistent with a value of mth > 5.3 keV from the recent analysis of the Ly α forest. We also identify two main sources of possible systematic errors and conclude that deeper investigations in the complex structure of lens galaxies as well as the size of the background sources should be a priority for this field.

scholarly journals LARGE SCALE STRUCTURE BY GLOBAL MONOPOLES AND COLD DARK MATTER

1992 ◽  
Vol 07 (10) ◽  
pp. 903-910 ◽  
Author(s):  
LEANDROS PERIVOLAROPOULOS
Keyword(s):  
Dark Matter ◽  
Cosmological Model ◽  
Gravitational Wave ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Mass Range ◽  
Large Scale Structure ◽  
Mass Function ◽  
Global Monopoles ◽  
Good Agreement

A cosmological model in which the primordial perturbations are provided by global monopoles and in which the dark matter is cold has several interesting features. The model is normalized by choosing its single parameter within the bounds obtained from gravitational wave constraints and by demanding coherent velocity flows of about 600 km/sec on scales of 50h-1 Mpc . Using this normalization, the model predicts the existence of dominant structures with mass 2×1016M⊙ on a scale 35h-1 Mpc , i.e., larger than the horizon at t ep . The magnitude of the predicted mass function in the galactic mass range is in good agreement with the observed Schechter function.

Cosmic background radiation anisotropy in an open inflation, cold dark matter cosmogony

1994 ◽  
Vol 434 ◽  
pp. L1 ◽  
Author(s):  
Marc Kamionkowski ◽  
Bharat Ratra ◽  
David N. Spergel ◽  
Naoshi Sugiyama
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Background Radiation ◽  
Cosmic Background Radiation ◽  
Cosmic Background

scholarly journals Galaxy Formation and Evolution: What to Expect from Hierarchical Clustering Models

1996 ◽  
Vol 171 ◽  
pp. 247-254 ◽  
Author(s):  
C.S. Frenk ◽  
C.M. Baugh ◽  
S. Cole
Keyword(s):  
Dark Matter ◽  
Hierarchical Clustering ◽  
Galaxy Formation ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Background Radiation ◽  
Gravitational Instability ◽  
Density Fluctuations ◽  
Galaxy Formation And Evolution ◽  
Microwave Background Radiation

In hierarchical clustering theories of galaxy formation, galaxies form by gas cooling and condensing into dark matter halos which, in turn, form by a hierarchy of mergers (White & Rees 1978). The context in which this process takes place is specified by a cosmological model that determines the spectrum of primordial density fluctuations and the rate at which they grow by gravitational instability. The best known example of such a model is the cold dark matter (CDM) model (see Frenk 1991 for a review), but a number of alternatives (mostly variants of CDM), have recently become popular in response to new data on large-scale structure and the COBE detection of anisotropies in the microwave background radiation.

scholarly journals Shell-crossing in a ΛCDM Universe

2020 ◽  
Vol 501 (1) ◽  
pp. L71-L75
Author(s):  
Cornelius Rampf ◽  
Oliver Hahn
Keyword(s):  
Dark Matter ◽  
Perturbation Theory ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Three Dimensional ◽  
Random Initial Data ◽  
Recursion Relations ◽  
Indispensable Tool ◽  
First Time ◽  
Very High

ABSTRACT Perturbation theory is an indispensable tool for studying the cosmic large-scale structure, and establishing its limits is therefore of utmost importance. One crucial limitation of perturbation theory is shell-crossing, which is the instance when cold-dark-matter trajectories intersect for the first time. We investigate Lagrangian perturbation theory (LPT) at very high orders in the vicinity of the first shell-crossing for random initial data in a realistic three-dimensional Universe. For this, we have numerically implemented the all-order recursion relations for the matter trajectories, from which the convergence of the LPT series at shell-crossing is established. Convergence studies performed at large orders reveal the nature of the convergence-limiting singularities. These singularities are not the well-known density singularities at shell-crossing but occur at later times when LPT already ceased to provide physically meaningful results.

scholarly journals The anisotropy of the power spectrum in periodic cosmological simulations

2021 ◽  
Vol 503 (4) ◽  
pp. 5638-5645
Author(s):  
Gábor Rácz ◽  
István Szapudi ◽  
István Csabai ◽  
László Dobos
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Initial Conditions ◽  
Power Spectra ◽  
Cosmological Simulations ◽  
Spherical Collapse ◽  
Lower Amplitude ◽  
Hydrodynamical Simulations

ABSTRACT The classical gravitational force on a torus is anisotropic and always lower than Newton’s 1/r2 law. We demonstrate the effects of periodicity in dark matter only N-body simulations of spherical collapse and standard Lambda cold dark matter (ΛCDM) initial conditions. Periodic boundary conditions cause an overall negative and anisotropic bias in cosmological simulations of cosmic structure formation. The lower amplitude of power spectra of small periodic simulations is a consequence of the missing large-scale modes and the equally important smaller periodic forces. The effect is most significant when the largest mildly non-linear scales are comparable to the linear size of the simulation box, as often is the case for high-resolution hydrodynamical simulations. Spherical collapse morphs into a shape similar to an octahedron. The anisotropic growth distorts the large-scale ΛCDM dark matter structures. We introduce the direction-dependent power spectrum invariant under the octahedral group of the simulation volume and show that the results break spherical symmetry.

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