Dark Matter:Dark Matter:What do we really know?What do we really know?

ICISE inauguration, Quy Nhon, August 11-17, 2013

Charling TAO tao@cppm.in2p3.fr

Centre de Physique des Particules de Marseille (CPPM), IN2P3, Marseille, France

Tsinghua Center for Astrophysics (THCA), Tsinghua University, Beijing, China

Dark Matter:Dark Matter:What do we really know?What do we really know?

DM: we know it exists in the Universe!

DM: - particle that does not emit observable radiation - interacts gravitationally… - non baryonic

Assuming standard Big bang Cosmology with GR

Wealth of astrophysical evidence for DM

Galaxy rotation curves (V. Rubin)

Dynamics of galaxy clusters (Zwicky)

X-ray clusters

Bullet cluster (Clowe+,2006)

Gravitational lensing mass reconstruction

4

Evidence for dark matter: clusters

Clusters velocity dispersion masses ~ 100 x visible mass

Zwicky ApJ 86 ,217 (1937): Coma Cluster velocities

April 18, 20015Galactic level: (!930’s) Oort discrepancy in the Milky Way disk: factor 2 now disappeared

Evidence for dark matter: rotation curves of spiral galaxies

V. Rubin 1970’s

A.Bosma

Some numbers ...

A galaxy like the Milky Way or Andromeda has a total visible mass of about 61010 Msun.

- rotation velocity is ~220 km/sec

- radius about ~30 kpc

Newton:

total mass: 3.31011 Msun

~5 times more mass than visible Local density 0.3- 0.4 GeV/cm3

G

RvM

R

GMv

2rot

rot G

RvM

R

GMv

2rot

rot

Evidence for dark matter:Gravitational Lensing:

GR: light trajectory bent by a gravitational field.

Perfectly Aligned Slightly Misaligned

Gravitational Lensing:a property of General Relativity

Evidence for dark matter: Bullet Cluster

X-ray vs gravitational lensing:

Gaz clearly separated from mass potential peaks

Clowe+2006

Dark Matter:Dark Matter:What do we really know?What do we really know?

DM common paradigm: it exists! - Contributes to energy density in the Universe, - Measured in clusters and galaxies

DM: - particle that does not emit observable radiation - interacts gravitationally… - non baryonic

The Universe energy density content after Planck

Wikipedia

Matter today ~ 31.7% energy density of the Universe

84.5% of the matter is dark matter

% precision

Cf Y. Giraud-Heraud‘s talk

What do we know about DM nature ?

Particle : stable? mass? interaction cross-sections? charge? spin ?

Constraints from non-observation in direct/indirect/LHC searchesAND

Observations in Astrophysics / Cosmology

Very different DM candidates

Modified Gravity

1Neutrino

2. WIMPsWeakly interactingmassive particles 10-1000GeV

3. Light axions

SIMPs

Exotica

MACHOs

Black holes

dust Cold Molecular Hydrogen

Snowmass 2013

Why WIMPs? “WIMP”= “Weakly Interacting” Massive Particles

G. Altarelli: « still most optimal candidates !»

Arguments in the 1980’s:

• Need for Cold Dark Matter from Large Scale Structures• Very good Particle physics candidate: SUSY LSP• Weak neutrino size cross sections expected which our

detectors Ge, NaI were sensitive to…

Why WIMPs? “WIMP”= “Weakly Interacting” Massive Particles

Assumption: DM= Relic Particles from Big Bang

If DM survives today

rate annihilation < rate expansion

If (rate annihilation << rate expansion),

too much DM today

At « freeze out »

< v > ~ 10-26/ h2 cm3/s

Scale of weak interactions !

Coincidence Coincidence with with W, Z physics?W, Z physics?

Searches for massive neutrinos cross sections exclude cross-section Searches for massive neutrinos cross sections exclude cross-section < 0.1 < 0.1

Argument in 80’s, now weaker?

Particle physics preferred DM: SUSY Neutralinos ?

˜ ˜ Z ˜ H 10 ˜ H 2

0

Look everywhere possibleLook everywhere possible !

Direct and Indirect

Detections

• A natural particle physics solution

• Stable linear combination gauginos and higgsinos (LSP)

• SUSY > 7 parameters MSSM no predictive power

• Experimental Constraints LEP, pp, b-->sLHC...

WIMP searches

MMN

Ge, Si, NaI, LXe, …

Direct detection Indirect detection

Accelerator particle production,

eg, LHC

p, e+

+ Galactic, cluster, Universe scales…

Sun, Earth, Galactic center, clumps?

Indirect Detection: Principle

SMMG

Accumulation

+

Annihilation

Astroparticle detectors:positrons, antiprotons, antideutons

gammas, neutrinos

MN (WIMPS)

Possible final states: +-, lepton pairs, qq, WH, ZH, WW, ZZ ; Hadronisation and decay

Non dedicated experiments Need discovery at accelerators!

Still hope at LHC ?

Astrophysical origin of observed signals,eg, AMS, are hard to exclude (cf Lee SC’s talk)

2500m2500m

300m300m

50m50m

Electro-opticalElectro-opticalunderwater cableunderwater cable ~40km ~40km

Junction boxJunction box

Readout Cables Readout Cables

Shore stationShore station

anchoranchor

floatfloat

Electronics Containers Electronics Containers

~60m~60mCompass,Compass,tilt metertilt meter

hydrophonehydrophone

Optical M Optical M odulesodules

acoustic detector acoustic detector

Cerenkov Light

track

BioluminescenceK40

Light Sources

WIMPs Indirect Detection

p, e+

-

Present limits Snowmass 2013

Neutrino limit: Billard+ 2013

WIMP search: direct detection

Cf. B. Sadoulet’s talk

Usual assumptions of DM distribution in our Galaxy

Usual h ypoheiDM= 0.3 GeV/cm3, =10-3,Maxwellian distribution of velocities, vrms=270 km/s

vSun=220 km/s

?

« Simplified Model »of Matter in our Galaxy:

SMMG

/)())/(1()/(

)()(

arar

rr c

Rotation curves

a = halo core radius

Isothermal profile 2 2 0

=0 without cusp

Navarro-Frenk-White 1 3 1

Mo Moore + 1.5 3 1.5)

Used for most comparisons…

But is it the reality? Clumps? Corotation?

Galactic scale N-body simulations with Baryons

Ling+ 2009 Dark Matter Direct Detection Signals inferred from a Cosmological N-body Simulation with Baryons

Fin2 DM populations : halo DM +disk DM only measurements can tellCDM simulation at small scales might have problems

DM properties from Large Scale Structures LSS

Cf beautiful movies of G. Smoot

Planck CMB map

Primordial perturbation seeds for structure formationDM potential wells

!Density perturbations collapse into DM haloes. Small Haloes merge into bigger haloes.

Gas in DM haloes collapse in galactic disks.

Structure formation: Bottom-up Scenario

Shapes of galaxies change over time.

Due to merging of haloes

Hubble TuningFork Diagram

Before 2000: Nature of DMHot or Cold?

CDM is non-relativistic

at decoupling,

Form structures in a

Hierarchical

bottom-up scenario.

HDM relativistic at decoupling

Mean free path large

Large structures form first

Comparisons of observations with pre-2000 N-body Simulations prefer

CDM

Collaboration VIRGO 1996http://www.mpa-garching.mpg.de/~virgo/virgo/

CDM

SCDM

CDM

OCDM

Z=3 Z=1 Z=0

OMEGA = 0.3LAMBDA = 0.7 H0 = 70 km/(Mpc sec)Sigma8 = 0.9

OMEGA = 1LAMBDA = 0H0 = 50 km/(Mpc sec)Sigma8 = 0.51

OMEGA = 0.3LAMBDA = 0 H0 = 70 km/(Mpc sec)Sigma8 = 0.85

OMEGA = 0.3LAMBDA = 0H0 = 50 km/(Mpc sec)Sigma8 = 0.51

N-Body simulations: CDM

Preferred paradigm:

Most N-Body simulations use stable CDM halos as seed for structures:

structures evolve, merge and cluster

- DM halos

- cuspy density profiles,

- Triaxial halos

- central density depends on the mass of the halo.

Universal Density Profilefrom N-body simulations

NFW Navarro, Frenk, White 1996

Cusp

Dark matter distribution—Density profiles

Cluster central density profile X-ray

~2000 : CDM crisis at small scales

Comparing data with N-body Simulations •cusp/core at GC•Missing galactic satellites

Galaxy profiles prefer core at center

CDM Simulations cusps(Navarro, Frenk, White 1996):

Observations favour Core profile

rotation curves

Problems at smaller scales?

Galaxy core vs cusp

Salucci & Frigerio Martins, 2009

Data prefer Burkert Core Profile

Predicted number

Observed number of luminous

satellite galaxies

Satellite galaxies are seen in Milky Way, e.g. Saggittarius, MCs

20km/s 100km/s10km/s

Too low number of visible Satellite galaxies

Alternatives to CDM

• Self-Interacting Dark Matter (Spergel & Steinhardt 2000)

• Strongly Interacting Massive Particle

• Annihilating DM

• Decaying DM (eg. Zhang XM+, Nguyen Quynh Lan in //

session)

• …

• WDM: reduce the small scale power

Norma G.Sanchez, Hector J. de Vega+… Chalonge series

DM Self-interaction constraints

DM particles might interact with themselves or other new particles, mediated by new, dark gauge bosons.

Interactions affect the structures of DM halos:

DM scatters energy and angular momentum transfers

For hard-sphere elastic scattering,

observations of the structure of galaxy clusters constraints σ /m

4.5 E-7 (t/E10 yr)-2 < /m <~ 1 cm2/g Bullet cluster

Williams & Saha 2011SL cluster analysis

< 0.02 elliptical core MS2137-23 Miralda-Escude 2002

Non neutral DM/CHAMPs

Strong constraints :

Charged (CHAMPS) or small electric or magnetic dipole moment

coupling to the photon-baryon fluid before recombination, alter the sub-degree-scale of CMB and matter power

spectrum.

Cf - Sigurdson+ , Dark-matter electric and magnetic dipole moments,

(2004);

- McDermott, H.-B. Yu, & K. M. Zurek, Turning off the lights: How dark is dark matter? (2011)

•"missing satellite problem'',

•''cusp-core problem'',

• mini-voids The sizes of mini-voids in the local universe: an argument in favor of a warm dark matter model? Tikhonov et al.

•HI determinations of velocity function profiles N-Body simulation Comparisons with Virgo results by Arecibo Legacy (ALFALFA)

“Evidence” for WDM ?

N-Body simulations: WDM

Stable WDM looks like stable CDM on scales> 10 Mpc,

- WDM create a cutoff in the matter power spectrum

At late times, the evolution of the matter power spectrum is more subtle as halos form.

Large WDM halos are virtually indistinguishable from stable CDM halos

somewhat less concentrated,

smaller halos, fluffier and less cuspy than CDM halos.

The subhalo mass function drops significantly on mass scales corresponding to that cutoff scale.

Does not solve everything

Nature of DMHot or Cold, or Warm?

CDM is non-relativistic

at decoupling, forms

structures in a hierarchical,

bottom-up scenario.

HDM is tightly bound byobservations and LSS formation

WDM?

WDM10 h/Mpc, keV

CLUES simulations, Yepes, 2010

WDM vs CDM

From Jing 2000

Density profileVelocity function

CDM vs WDM: HI velocity functions

Virgo and Anti Virgo directions

No simple feedback mechanism to explain the factor 10 depletion from CDM?

arXiv:1005.2687: Constrained Local UniversE Simulations (CLUES)

Gottloeber, Hoffman , Yepes

Velocity widths in Galaxies

Velocity widths in galaxies from 21 cm HI surveysPapastergis et al, 2011; Zavala et al., 2009NB: The red curve is for 1 keV WDM

Limits on mass of eventual WDM particles

• Stellar dynamics in MW satellites (Boyanovsky, de Vega, Sanchez

2008; de Vega and Sanchez 2009)

• High-z QSO LF (e.g. Song and Lee 2009)

• Ly-alpha forest to constrain P(k) at small scales and different

z’s (Most popular method: Narayanan et al 2000; Viel et al 2005;2008)

• Ly-a + SDSS results (Boyarsky et al 2009)

• QSO lensing ( Miranda & Maccio 2007 )

• Abundance of dwarf satellites of MW (Maccio & Fontanot 2010;

Polysensky & Ricotti, 2010)

Mass WDM ~ 1- 5 keV

A fashionable (?) candidate Sterile neutrinos

Constraints on sterile neutrinos

~2000 :Problems with CDM at small scales

Comparing data with N-body Simulations •Galactic satellites•cusp/core at GC

Problems can perhaps be solved with better resolution and additional physics in N-Body simulations (SN, AGN feedback, stellar winds…)

Ma Chung Pei, Chang, P., Zhang, 2009

Einasto vs NFW

CDM Simulations cuspsrather Einasto profiles than NFW

Missing satellites: CDM way out

• satellites do exist, but star formation suppressed (after reionization?)

• satellites orbit do not bring them to close interaction with disk, so they will not heat up the disk.

• Local Group dwarf velocity dispersion underestimated

• Galaxies may not follow dwarves

Halo substructures may be probed by -Lensing-local Milky Way structures

More faint or dark galaxies discovered

Eg, Belokurov et al, 2010

Nature of dark matter or astrophysics process?

What we know:

Comparisons of observations with N-body Simulations today

prefer Non-Hot DM

12/16/2009 70

Mandelbaum et al. (2006)

Stacked galaxy—galaxy weak lensing signal fit with various profiles.

CL0024

Tyson, Kochanski, & Dell’Antonio (1998)

Probing DM Particle properties

Progress in Gravitational Lensing

• Weak lensing

• Flexion

• Strong lensing arclets

“Weak Lensing”

Distorsion of galaxy shapes by foreground matter

without lensing Lensing effect

Weak Lensing mass reconstruction

RXJ1347.5-1145 (Bradac et al 2005)

Image ellipticity -> shear->

invert the equation

Galaxy-scale DM density profile

Generalized NFW model → Dark Matter mass

Sensitivity of detection scales by lensing

Weak lensing: < 100 kpc

Flexion: 10-100 kpc

Strong lensing: 1-10 kpc

Surface density profile measurements obtained from galaxy groups

in the COSMOS survey Leauthaud et al. 2010

Dec 2012

Galaxy-galaxy lensing

Measure the correlation of shear of the background galaxies with mass of the foreground galaxies

To achieve the galaxy-galaxy lensing signal, we need two important ingredients that we can extract from the data

1)redshift distribution of the lensed background galaxies

2)shape of the lensed background galaxies

Future Measurements of DM properties with lensing

From 100 sq deg scale at CFHT to 5000 – 20000 sq deg sky surveys

KDUST?

BigBoss-like/MS-DESI can provide 3D

WFIRST?

Euclid slide + new logo

Cosmic shear power spectra Markovic et al. 2010 Euclid-like DE space survey +Planck:

Integral effects → better than matter power spectrum

Sensitive to m_WDM < 2.5 keV

keV WDM effect around k=10 h/Mpc

Issues• Galaxy evolution alters DM halos and the matter

power spectrum .Rudd, Zentner & Kravtsov, Effects of Baryons and Dissipation on the

Matter Power Spectrum (2008);

Pedrosa,Tissera, & Scannapieco, The joint evolution of baryons and dark matter halos, (2010);

Scannapieco +, The Aquila Comparison Project: The Effects of Feedback and Numerical Methods on Simulations of Galaxy Formation, arXiv:1112.0315.

• Most of the simulations (even today) are DM-only

- DM halos extremely sensitive to the implementation of the galaxy physics in the codes.

- DM halo morphologies and galaxy properties need resolutions: giant molecular cloud (GMC) sized regions .

But a lot of concern/work in the last 3 years.

Caveat: Strong Reliance on N-body Caveat: Strong Reliance on N-body simulations simulations

might be misleading!might be misleading!

More recent comparisons of WDM and CDM simulations.

eg Gao+, Jing+ , Yepes+ ,

- Non-linear collapse of WDM structures

N-Body simulations with baryons

Jing Y. (2005)

Baryon physics (eg.,AGN feedback) affects Matter Power

SpectrumSemboloni+ (2011)

Van Daalen+(2011)

Shale + :OWLS simulation

Consequences on WL

cosmological parameters fits

Baryon effects different from neutrino effects

Semboloni et al. 2011

Dark Matter:Dark Matter:What do we really know?What do we really know?

Or Do We Really?

DM: we know it exists!

DM: - particles that does not emit observable radiation - interacts gravitationally… - non baryonic

Alternatives to DM?

Not so many models any more, but still… some are still doubting:

eg http://www.astro.uni-bonn.de/~pavel/kroupa_SciLogs.html

Famaey & Mc Gaugh Living Reviews in Relativity, vol. 15, no. 10 2012

- MOND- Milgrom /TEVES-Beckenstein needs neutrinos to explain Bullet Cluster…

- MOG : Moffat and collaborators

Scalar-Tensor-Vector Model of gravity : “few parameters can explain away DE and DM”.

Main observational argument for alternative to DM

Local Universe: - Velocity analysis

local density ~ 0.07-0.08

- Dwarf galaxies: observed ones seem to be

Tidal dwarf galaxies not expected to be dominant with DM models but seem to be observationnally in disk of Milky Way and Andromeda

How representative is it?

Universe with Torsion

- Extension to GR:

in simplest CARTAN model :

(eg, Schucker and Tilquin)

Lambda/DE still needed but… DM reduced (to zero?)

- Difficulties with many extensions

eg Gauss theorem not valid, pathologies…

Summary: What do we know about DM?

• Astrophysical observations

existence of non baryonic Dark Matter

• N-Body simulations and Observations of LSS

existence of not-hot DM?

. Many problems with CDM simulations can be solved with

O(1keV) WDM or Baryon physics ?

• More work on baryonic N-body simulations needed!

We love CDM but need to find CDM in accelerators and DD/ID experiments!

A mysterious Dark Universe !

Graph source: Wikipedia

What we know is only 4-5 %

of the energy density of the Universe

We now measure with precision the extent of our ignorance !

cảm ơn bạn Thank you

谢谢

Towards a large South Pole Dome A Kunlun Dark Universe Survey Telescope

(KDUST) Multiprobe measurements (SNIa, Weak Lensing, BAO, Clusters) for

cosmology and ancillary science

First stage 2011-2015: 3 x 67 cms telescopes

(AST3)

- one AST3 installed in Dome A in fall 2011,

THCA contributes to one AST3 and take responsibility for SN search (need computing capability)

- Collaboration with Australia, US and France

2.5 m KPATH (Kunlun Pathfinder): 2013(?)-2017

Larger (> 4m) KDUST:

Timescale too early to define!

Antarctica Schmidt Telescopes (AST3)

Aperture ： 67 cm；FOV ： 4.2°；Wave Band ： 400nm-900nm ( i,g, r, or IR? filter for 3 telescopes );

Scale ： 1 arcsec/pixel;

Image quality ： 80 ％ energy encircled in one pixel；CCD: 9micron /pixel, 10580x10560 (95.22mm x 95.05mm image

area)；Type: STA1600；

Working mode: frame transfer readout

Focal length: 1867mm

Distorsion in the whole field: 0.012% (less than 1 pixel)

Total optical length: 2.2m

First AST3 in Dome A, some data in 2012

Dec 2011 in Dome ASummer 2011 in Xuyu

The Kunlun Dark Universe Survey Telescope

5000 sq deg down to mag 29