A model for the mass and distribution of particles in dark matter halos

2018 ◽  
Vol 96 (11) ◽  
pp. 1178-1182
Author(s):  
Allan Runstedtler
Keyword(s):  
Dark Matter ◽  
Total Mass ◽  
Classical Model ◽  
Variable Density ◽  
Particle Mass ◽  
Quantum Model ◽  
Dark Matter Halos ◽  
Quantum Uncertainty ◽  
System Temperature ◽  
Straightforward Solution

This model is intended for dark-matter-dominated galaxies and galaxy clusters for which the centrifugal force caused by system rotation is negligible. Such systems, ostensibly dark matter halos, would tend to be spherical. Consider a uniform sphere of identical, massive particles in equilibrium (not contracting or expanding). In the quantum model, gravitation pulls the particles together and quantum uncertainty pushes them apart. In the corresponding classical model, gravitation pulls the particles together and thermal motion pushes them apart. This model provides an expression for particle mass as a function of the total mass and density of the system and its quantum state or temperature. Using the measured total mass and density of our dark-matter-dominated galaxy, and assuming the system is in the ground state, the particle mass is found to be 10.5 eV and the temperature 0.042 K. This represents the lowest possible system temperature and particle mass. If, on the other hand, the system is in equilibrium with the cosmic microwave background, the particle mass is found to be 693 eV. This range of inferred particle masses supports the hypothesis of “low-mass dark matter” with approximate mass 100 eV. However, the system temperature is not presently known so it is possible that the temperature is higher and, consequently, the particles are heavier. The average speed of the particles is found to be approximately 1/1000 the speed of light in our galaxy. Remarkably, this result does not depend on the system temperature and, therefore, does not depend on the particle mass. The extension of this model to variable density provides a straightforward solution to the “core-cusp problem” because the distribution of dark matter that minimizes the system energy has a flat central dark matter density profile.

scholarly journals Figure Rotation of Dark Halos in Cold Dark Matter Simulations

2006 ◽  
Vol 2 (S235) ◽  
pp. 80-80
Author(s):  
S.E. Bryan ◽  
C.M. Cress
Keyword(s):  
Dark Matter ◽  
Normal Distribution ◽  
Total Mass ◽  
Cold Dark Matter ◽  
Rotation Speed ◽  
Dark Matter Halos ◽  
Average Rotation ◽  
Log Normal ◽  
Figure Rotation ◽  
Log Normal Distribution

AbstractWe investigate the rotation of dark matter halos identified in ΛCDM simulations. After removing halos that contain a significant amount of substructure, about 82% of the remaining halos were found to undergo coherent rotation over 5h−1 Gyr. The rotation speeds follow a log-normal distribution. The average rotation speed of a halo was 0.11h rads/Gyr. Less than half of the selected halos showed alignment between their rotation and minor axes. We found no correlation between halo properties, such as total mass, and the rotation speed.

Constraints on the Clumpiness of Dark Matter Halos Through Heating of Disk Galaxies

2003 ◽  
Vol 10 ◽  
pp. 95-95
Author(s):  
E. Ardi ◽  
T. Tsuchiya ◽  
A. Burkert
Keyword(s):  
Dark Matter ◽  
Disk Galaxies ◽  
Dark Matter Halos

Constrained Simulations of Dark Matter Halos

2006 ◽  
Vol 20 ◽  
pp. 15-18
Author(s):  
Y. Hoffman ◽  
E. Romano-Díaz ◽  
A. Faltenbacher ◽  
D. Jones ◽  
C. Heller ◽  
...  
Keyword(s):  
Dark Matter ◽  
Dark Matter Halos

scholarly journals Modeling dark matter halos with nonlinear field theories

2021 ◽  
Vol 103 (10) ◽  
Author(s):  
R. A. C. Correa ◽  
P. H. R. S. Moraes ◽  
A. de Souza Dutra ◽  
O. L. Dors ◽  
W. de Paula ◽  
...  
Keyword(s):  
Dark Matter ◽  
Field Theories ◽  
Dark Matter Halos ◽  
Nonlinear Field

scholarly journals On the formation and stability of fermionic dark matter halos in a cosmological framework

2020 ◽  
Author(s):  
Carlos R Argüelles ◽  
Manuel I Díaz ◽  
Andreas Krut ◽  
Rafael Yunis
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Space Distribution ◽  
Coarse Grained ◽  
Dark Matter Halos ◽  
The Core ◽  
The Galaxy ◽  
Gravitating Systems ◽  
The Given ◽  
First Time

Abstract The formation and stability of collisionless self-gravitating systems is a long standing problem, which dates back to the work of D. Lynden-Bell on violent relaxation, and extends to the issue of virialization of dark matter (DM) halos. An important prediction of such a relaxation process is that spherical equilibrium states can be described by a Fermi-Dirac phase-space distribution, when the extremization of a coarse-grained entropy is reached. In the case of DM fermions, the most general solution develops a degenerate compact core surrounded by a diluted halo. As shown recently, the latter is able to explain the galaxy rotation curves while the DM core can mimic the central black hole. A yet open problem is whether this kind of astrophysical core-halo configurations can form at all, and if they remain stable within cosmological timescales. We assess these issues by performing a thermodynamic stability analysis in the microcanonical ensemble for solutions with given particle number at halo virialization in a cosmological framework. For the first time we demonstrate that the above core-halo DM profiles are stable (i.e. maxima of entropy) and extremely long lived. We find the existence of a critical point at the onset of instability of the core-halo solutions, where the fermion-core collapses towards a supermassive black hole. For particle masses in the keV range, the core-collapse can only occur for Mvir ≳ E9M⊙ starting at zvir ≈ 10 in the given cosmological framework. Our results prove that DM halos with a core-halo morphology are a very plausible outcome within nonlinear stages of structure formation.

Clustering dependence of Chandra COSMOS Legacy AGN on host galaxy properties

2019 ◽  
Vol 15 (S356) ◽  
pp. 226-226
Author(s):  
Viola Allevato
Keyword(s):  
Dark Matter ◽  
Formation Rate ◽  
Stellar Mass ◽  
Active Galaxies ◽  
Host Galaxy ◽  
Mass Star ◽  
Mass Relation ◽  
Dark Matter Halos ◽  
X Ray

AbstractThe presence of a super massive BH in almost all galaxies in the Universe is an accepted paradigm in astronomy. How these BHs form and how they co-evolve with the host galaxy is one of the most intriguing unanswered problems in modern Cosmology and of extreme relevance to understand the issue of galaxy formation. Clustering measurements can powerfully test theoretical model predictions of BH triggering scenarios and put constraints on the typical environment where AGN live in, through the connection with their host dark matter halos. In this talk, I will present some recent results on the AGN clustering dependence on host galaxy properties, such as galaxy stellar mass, star formation rate and specific BH accretion rate, based on X-ray selected Chandra COSMOS Legacy Type 2 AGN. We found no significant AGN clustering dependence on galaxy stellar mass and specif BHAR for Type 2 COSMOS AGN at mean z ∼ 1.1, with a stellar - halo mass relation flatter than predicted for non active galaxies in the Mstar range probed by our sample. We also observed a negative clustering dependence on SFR, with AGN hosting halo mass increasing with decreasing SFR. Mock catalogs of active galaxies in hosting dark matter halos with logMh[Msun] > 12.5, matched to have the same X-ray luminosity, stellar mass and BHAR of COSMOS AGN predict the observed Mstar - Mh, BHAR - Mh and SFR-Mh relations, at z ∼ 1.

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