scholarly journals Two-integral distribution functions in axisymmetric galaxies: Implications for dark matter searches

2019 ◽  
Vol 99 (4) ◽  
Author(s):  
Mihael Petač ◽  
Piero Ullio
Keyword(s):  
Dark Matter ◽  
Distribution Functions ◽  
Integral Distribution

scholarly journals Anisotropic Distribution Functions for the Elliptical Galaxy NGC 1600

1996 ◽  
Vol 171 ◽  
pp. 413-413
Author(s):  
Michael Matthias ◽  
Ortwin Gerhard
Keyword(s):  
Perturbation Theory ◽  
Elliptical Galaxy ◽  
Major Axis ◽  
Distribution Functions ◽  
Minor Axis ◽  
Dynamical Models ◽  
Ccd Photometry ◽  
Radial Anisotropy ◽  
Best Fitting ◽  
Integral Distribution

Three-integral (3I) dynamical models for NGC 1600 were constructed as follows: (i) Lucy-inversion of CCD photometry and gravitational potential as in Binney, Davies, Illingworth (ApJ 361, 78, 1990), assuming axisymmetry. (ii) Third integral by perturbation theory as in Gerhard & Saha (MN 261, 311, 1991). (iii) Two- and three-integral distribution functions as in Dehnen & Gerhard (MN 261, 311, 1993), assuming various anisotropy patterns. The kinematic results from these models are presented in Fig. 1. The best-fitting 3I model (solid line, right panels) has outward-increasing radial anisotropy on the major axis and is nearly isotropic on the minor axis. The M/L of the various 3I-models varies only slightly around M/L=6.2.

scholarly journals DISTRIBUTION FUNCTION OF DARK MATTER WITH CONSTANT ANISOTROPY

2008 ◽  
Vol 17 (08) ◽  
pp. 1283-1294 ◽  
Author(s):  
DING MA ◽  
PING HE
Keyword(s):  
Dark Matter ◽  
Asymptotic Behavior ◽  
Density Profile ◽  
Anisotropy Parameter ◽  
Outer Part ◽  
Distribution Functions ◽  
Dark Matter Halos ◽  
Spherical Models ◽  
Two Parameters ◽  
Inner Parts

N-body simulations of dark matter halos show that the density is cusped near the center of the halo. The density profile behaves as r–γ in the inner parts, where γ ≃ 1 for the NFW model and γ ≃ 1.5 for the Moore model, but in the outer parts the two models agree with each other in the asymptotic behavior of the density profile. The simulations also show information about the anisotropy parameter β(r) of the velocity distribution: β ≈ 0 in the inner part and β ≈ 0.5 (radially anisotropic) in the outer part of the halo. We provide some distribution functions F(E, L) with the constant anisotropy parameter β for the two spherical models of dark matter halos: a new generalized NFW model and a generalized Moore model. There are two parameters α and ∊ for those two generalized models to determine the asymptotic behavior of the density profile. In this paper, we concentrate on the situation of β(r) = 1/2 from the viewpoint of the simulation.

scholarly journals Constraining scatter in the stellar mass–halo mass relation for haloes less massive than the Milky Way

2019 ◽  
Vol 488 (4) ◽  
pp. 4916-4925 ◽  
Author(s):  
Magdelena Allen ◽  
Peter Behroozi ◽  
Chung-Pei Ma
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Stellar Mass ◽  
Distribution Functions ◽  
Sloan Digital Sky Survey ◽  
Data Sets ◽  
Mass Relation ◽  
Velocity Distribution Functions ◽  
Halo Masses ◽  
Stellar Masses

ABSTRACT Most galaxies are hosted by massive, invisible dark matter haloes, yet little is known about the scatter in the stellar mass–halo mass relation for galaxies with host halo masses Mh ≤ 1011M⊙. Using mock catalogues based on dark matter simulations, we find that two observable signatures are sensitive to scatter in the stellar mass–halo mass relation even at these mass scales; i.e. conditional stellar mass functions and velocity distribution functions for neighbouring galaxies. We compute these observables for  179,373 galaxies in the Sloan Digital Sky Survey (SDSS) with stellar masses M* > 109 M⊙ and redshifts 0.01 < z < 0.307. We then compare to mock observations generated from the Bolshoi-Planck dark matter simulation for stellar mass–halo mass scatters ranging from 0 to 0.6 dex. The observed results are consistent with simulated results for most values of scatter (<0.6 dex), and SDSS statistics are insufficient to provide firm constraints. However, this method could provide much tighter constraints on stellar mass–halo mass scatter in the future if applied to larger data sets, especially the anticipated Dark Energy Spectroscopic Instrument Bright Galaxy Survey. Constraining the value of scatter could have important implications for galaxy formation and evolution.

scholarly journals The dark matter distribution function and halo thermalization from the Eddington equation in galaxies

2016 ◽  
Vol 31 (13) ◽  
pp. 1650073 ◽  
Author(s):  
H. J. de Vega ◽  
N. G. Sanchez
Keyword(s):  
Dark Matter ◽  
Distribution Function ◽  
Equation Of State ◽  
Globular Clusters ◽  
Boltzmann Distribution ◽  
Distribution Functions ◽  
Local Thermal Equilibrium ◽  
Density Profiles ◽  
Starting Point ◽  
Analytic Expressions

We find the distribution function [Formula: see text] for dark matter (DM) halos in galaxies and the corresponding equation of state from the (empirical) DM density profiles derived from observations. We solve for DM in galaxies the analogous of the Eddington equation originally used for the gas of stars in globular clusters. The observed density profiles are a good realistic starting point and the distribution functions derived from them are realistic. We do not make any assumption about the DM nature, the methods developed here apply to any DM kind, though all results are consistent with warm dark matter (WDM). With these methods we find: (i) Cored density profiles behaving quadratically for small distances [Formula: see text] produce distribution functions which are finite and positive at the halo center while cusped density profiles always produce divergent distribution functions at the center. (ii) Cored density profiles produce approximate thermal Boltzmann distribution functions for [Formula: see text] where [Formula: see text] is the halo radius. (iii) Analytic expressions for the dispersion velocity and the pressure are derived yielding at each halo point an ideal DM gas equation of state with local temperature [Formula: see text]. [Formula: see text] turns out to be constant in the same region where the distribution function is thermal and exhibits the same temperature within the percent. The self-gravitating DM gas can thermalize despite being collisionless because it is an ergodic system. (iv) The DM halo can be consistently considered at local thermal equilibrium with: (a) a constant temperature [Formula: see text] for [Formula: see text], (b) a space dependent temperature [Formula: see text] for [Formula: see text], which slowly decreases with [Formula: see text]. That is, the DM halo is realistically a collisionless self-gravitating thermal gas for [Formula: see text]. (v) [Formula: see text] outside the halo radius nicely follows the decrease of the circular velocity squared.

scholarly journals On the Dynamics of very Flattened Ellipticals

1996 ◽  
Vol 171 ◽  
pp. 360-360 ◽  
Author(s):  
H. Dejonghe ◽  
V. de Bruyne ◽  
P. Vauterin ◽  
W.W. Zeilinger
Keyword(s):  
Data Analysis ◽  
Phase Space ◽  
Space Structure ◽  
Distribution Functions ◽  
Kinematic Data ◽  
Dust Lane ◽  
Phase Space Structure ◽  
Nuclear Dust ◽  
Integral Distribution

Our aim is to study the generic phase-space structure of flattened ellipticals by investigating a few typical cases. Here we report on the E4 elliptical NGC 4697.The construction of 2-integral and 3-integral distribution functions asks for photometry and kinematic data. In the course of the data analysis, we additionally detected a nuclear dust lane at 3.4″ or 0.4 kpc from the centre, which could be confirmed with HST data. This was put to good use to constrain the inclination.

scholarly journals Two-integral distribution functions for axisymmetric galaxies

1993 ◽  
Vol 153 ◽  
pp. 357-358
Author(s):  
C. Hunter ◽  
E. Qian
Keyword(s):  
Distribution Function ◽  
Angular Momentum ◽  
Stellar System ◽  
Distribution Functions ◽  
New Method ◽  
Integral Distribution ◽  
Axis Of Symmetry

We present a new method for finding a distribution function f, which depends only on the two classical integrals of energy E and angular momentum J about the axis of symmetry, for a stellar system with a known axisymmetric potential and density.

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