january 25, 2006 ncw, nice 1 1 caustics in dark matter halos sergei shandarin, university of kansas...

January 25, 2006January 25, 2006 NCW, NiceNCW, Nice 11

Caustics in Dark Matter Halos

Caustics in Dark Matter HalosSergei Shandarin, University of Kansas

(collaboration with Roya Mohayaee, IAP)

Nonlinear Cosmology Program: Nice-Marseille-Paris

Sergei Shandarin, University of Kansas

(collaboration with Roya Mohayaee, IAP)

Nonlinear Cosmology Program: Nice-Marseille-Paris


OutlineOutline

LCDM and LWDM models Introduction to caustics: 1D and 2D cases 3D universe Summary 1 What kills caustics? Summary 2



A big question: what is the dark matter?

A big question: what is the dark matter?

DIRECT DETECTIONINDIRECT DETECTION

Annihilation of self-annihilatedaxions and neutralinos producesgamma-raysHESS, GLAST experimentsAharonian et al 2005, Science

Weak lensinge.g. Gavazzi, Mohayee, Fort 2005

e.g. Sikivie, Ipser 1992Sikivie, Tkachev, Wang 1997: role of internal and external caustics


Unresolved problems in LCDM Reduction of satellite halos

Kauffmann et al 1993; Klypin et al 1999; Moore et al 1999; Willman et al 2004

Reduction of galaxies in voids Peebles 2001; Bode et al 2001

Low concentration of DM in galaxies Dalcanton & Hogan 2001; van den Bosch & Swaters 2001; Zentner & Bullock 2002; Abazajian et al 2005

Angular momentum problem and formation of disk galaxies

Dolgov & Sommer-Larson 2001; Governato et al 2004;

Kormendy & Fisher 2005

Possible solution: Warm Dark Matter


Lamda Warm Dark Matter

(LWDM)

Lamda Warm Dark Matter

(LWDM)

Abazajian 20051.7 keV < m < 8.2 keV


Why caustics?Why caustics?

Saichev 1976

For 100 GeV SUSY neutralino (LCDM)

For a few keV sterile neutrino or gravitino (LWDM)

Galaxy formation is not hierarchical or only marginally hierarchical! ( only a few mergers results in the halo of galactic size)


Caustics in geometric optics

Caustics in geometric optics


Generic singularities in 1DGeneric singularities in 1D

Points at a generic instant of time

Points at particular instants of time

Arnol’d, Shandarin, Zel’dovich 1982


Collisionless DM and collisional baryons

Collisionless DM and collisional baryons

Shandarin, Zel’dovich 1989

Dark matter

Baryons


Zel’dovich ApproximationZel’dovich Approximation

in comoving coordinates

potential perturbations

Density

are eigen values of

is a symmetric tensor

Density becomes



Lines (1D) at a generic instant of time

Points (0D) at a generic instant of time

Points (0D) at particular instants of time




Zel’dovichApproximation (2D)

N-body simulations (2D)

versus


2D N-body simulations (discreteness effect)


Melott, Shandarin 1989


Caustics in high

resolution

2D Simulatio

ns

Caustics in high

resolution

2D Simulatio

ns


2D vs 3D2D vs 3D

2D simulations 3D simulations

Melott, Shandarin 1989 Shirokov, Bertschinger 2005


QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Shirokov, Bertschinger 2005


Complexity of caustics(2D simulations)

Complexity of caustics(2D simulations)

Melott, Shandarin 1989


OutlineOutline



z=153

z=7.2

z=86z=115

z=0z=1

LCDM simulation (Diemand et al 2005)


* Hierarchical clustering

* Smallest halos

* Hierarchical clustering

* Smallest halos


LWDM simulations

m_x = 1.2 h^(5/4)) keV

Gotz & Sommer-Larson 2003



Lines (1D) at a generic instant of time

Surfaces (2D) at a generic instant of time







Caustics in hot systems

Caustics in hot systems

Colombi, Touma 2005


Summary 1Summary 1

Formation of caustics in dark matter halos (structures) is a more universal phenomenon than many cosmologists thought

before. Caustics have a complex geometry. The generic caustics can be

Surfaceses (2D) Lines (1D) Points (0D) at generic time Points (0D) at particular times

Exiting prospect: testing particle physics using caustics in DM halos.

Formation of caustics in dark matter halos (structures) is a more universal phenomenon than many cosmologists thought

before. Caustics have a complex geometry. The generic caustics can be

Surfaceses (2D) Lines (1D) Points (0D) at generic time Points (0D) at particular times

Exiting prospect: testing particle physics using caustics in DM halos.


Three things that destroy caustics.

Three things that destroy caustics.

• Discreteness (numerical, not physical)

• Phase-space becomes too fine-grained eventually reaching the physical discreatness (physical)

• Thermal velocity dispersion (physical)


Phase space becomes too fine-

grained

Phase space becomes too fine-

grained

Colombi, Touma 2005


Self-similar spherically symmetric solution

Self-similar spherically symmetric solution

Fillmore & Goldreich 1984; Bertschinger 1985

Equation of motion


Nondimensional EquationNondimensional Equation

Initial condition


Function

Function

Bertschinger 1985

At constant q:trajectory of particle

At constant \tau:positions of particles

Two interpretations


Density near caustics



Density (cold medium)Density (cold medium)




Tully 2005

NGC 5846


Effect of thermal velocity dispersion


Initial condition in coldmedium




Distance of the caustic in stream Distance of the caustic in stream v from the caustic in stream v=0v from the caustic in stream v=0


Universal density profiles in the vicinity of caustics

Universal density profiles in the vicinity of caustics


Gravitational cooling

Mohayaee, Shandarin 2005


Summary 2Summary 2

Spherical (self-similar) model can be used as a guideline More realistic models are badly needed Other singularities may be more interesting for

annihilation detection provided that they can be resolved Evolution in phase space needs to be studied in more

detail

Spherical (self-similar) model can be used as a guideline More realistic models are badly needed Other singularities may be more interesting for

annihilation detection provided that they can be resolved Evolution in phase space needs to be studied in more

detail

january 25, 2006 ncw, nice 1 1 caustics in dark matter halos sergei shandarin, university of kansas...

Documents

d simulations ncw

d cases

d universe summary

generic instant of timepoints

abazajian et

governato et

klypin et

willman et