Viktor Zacek, Université de Montréal

DARK MATTER

Lake Louise Winter Institute

February 2007

Part I

Lecture I

• Astronomical evidences for Dark Matter

• Dark Matter and the Dynamics of the Universe

• Present knowledge of the matter content of the Universe

• Dark Matter and structure formation

Lecture II

• Dark Matter candidates (MOND, neutrinos, axions, …)

• Neutralino interactions with Matter

• Status of indirect search experiments

• Status of direct search experiments

• Future directions

The Universe is infinite

and cyclic !

(Anaximander)

The Uiverse is finite, static and ever lasting.

(Aristoteles)

The Universe is a big rectangular box with Egypt at the center.

(the Egyptians)The Universe is a gigantic

vortex! (Aristophanes)

If God th

e Almighty would only have

consulted m

e before creation, I w

ould

have proposed something simpler.

(A.de Rujula)

The World was created on October

22, 4004BC at 6 o’clock in the evening.

(Bishop Ussher 1650)The visible Universe is only a fraction of the total Universe, it is 13.7 billion years old, with flat geometry and most of its mass is non-baryonic

(WMPA March 2006)

THE DARK MATTER PROBLEM - FIRST INDICATIONS

• Studies kinetic energies of 8 galaxies of the Coma Cluster

finds velocities are much larger than expected

apparently Coma cluster contains 200 x more mass than is visible in form of galaxies

The “hidden mass” problem becomes a “key problem” of modern cosmology

Fritz Zwicky, 1937

Doppler shift of star light and of HI distribution

Mhalo > 10 x (Mlum + Mgas)

2

2 )(

r

rGM

r

vrot

M(r) mass within r

M increses linearly for vrot = ct.

for large r halos of galaxies start to overlap

DARK MATTER & GALACTIC ROTATION CURVES

rv

1

Vera Rubin, 1974

2MASS two Micron All Sky Survey

DARK MATTER IN OUR MILKY WAY

G

rvrM rot

2

)(

…only 5-10% of matter visible!

DM 0.3 mp/cm3

1kpc = 3.259 103 Ly

VIRGOHI21: A GALAXY OF DARK MATTER ! (50 M Ly)

Visible spectrumRF-hydrogen emission

1000 x more Dark Matter than hydrogen!

M 0.1 MMW

(Feb. 2005)

DARK MATTER AROUND OTHER GALAXIES

Abell 2029

a cluster of thousands of galaxies

surrounded by gigantic clouds of hot gas

T 106 K

MTot> 10 Mvis

Size of Local group 2.2 MLy

MW & M31 dominate Local Group

Enormous gravit. pull between the two galaxies

Invisible mass > 10 x MMW

Local group at fringe of Virgo cluster

V= 3x105 km/h

v 1.6x106 km/h

Size of Virgo cluster 50MLy

Local group pulled towards Virgo cluster

invisible mass > 10 x Mvis

Virgo Cluster pulled towards

an invisible “Great Attractor”

v 2 x 106 km/h

DARK MATTER AT LARGER SCALES

Virgo cluster

DARK MATTER AT AT LARGE SCALES

Gravitational lensing

provides evidence of large masses between source and MW

recently 3D reconstruction of clusters of Dark Matter

HST CL0024+1654

Mdark>50 Mvis

THE BULLET CLUSTER IE0657-56 (3.4 109 LY)

M. Markewitch et al: HST, Magellan, Chandra (August 2006)

High velocity merger of clusters of galaxies 4500 km/s

108K

Mdark > 49 Mvis

Ekin + Epot = Etot

m

M

R

« Friedmann equation »

M = mass of Universe

R = radius of Universe

m = mass of a border

galaxy

adds to gravitation!

Energy density of vacuum

v = c2/8G

totERcmR

GMmR

m )

6

1(

2222

.

DARK MATTER & DYNAMICS OF THE UNIVERSE

R

mMGEpot

)3

4( 3R

R

mGE v

vpot

2

2R

mEkin

attractive repulsive

2)

6

1(

2

2222

. mckERcm

R

GMmR

mtot

RcmR

MmG

dR

dEF pot 2

2 3

1 k : curvature of space!

k = 0: flat

k > 0: closed

k < 0 open

(Robertson-Walker metric)

THE FRIEDMANN EQUATION

gTc

GRgR

4

8

2

1A. Einstein:

H0= 72 km s-1Mpc-1 (today!)

v = H0R Hubbles law!

v = c2/8G

Friedmann equation

2

22

2

)(3

8)(

R

kcGtH

R

RV

)()()( tRtHtR

HUBBLES LAW & CRITICAL DENSITY

G

Hc

8

3 2

“critical density” k = 0 (for =0)

2)

6

1(

2

2222

. mckERcm

R

GMmR

mtot

tot > 1 closed U.

tot < 1 open U.

tot = 1 flat, euclidean, critical U.

mtot

Mass parameter m = 0/ c =v/c 0: present day value

THE CRITICAL DENSITY

today:

c = 1.9 10-26 kg/m3

1proton/m3

= 0

...but lum 0.01 ( 1!)

G

Hc

8

3 2

HOW TO MEASURE ?

Count all the components of the Universe!

Luminous matter, stars

DM from galaxies and their rotation curves

DM in clusters of galaxies

DM inferred from x-ray clouds around clusters of galaxies

DM from large scale flows of galaxies

DM by gravitational lensing

+ Measure the geometry of the Universe!

Courtesy CERN

n + p D

p + D 3He

n + D T

T + p 4 He3He + n 4HeD + D 4HeHe + T 7Li

…well understood

no elements A = 5 / 8

heavy elements @ T ~ 106 y

Yi = fct( b, T, n, n , …)

light el. abund. consistent over O(9)

B FROM BIG BANG NUCLEOSYNTHESIS

b = 0.04 0.007

m ~ 0.2-0.3 Galaxy kinematics

Hot X-ray gas

Lensing

Velocity flows

Rotation curves

CURRENT EVIDENCE FOR m

SN Type Ia Redshift

m = 0.3, = 0.7

CURRENT EVIDENCE FOR

2003

…AND THERE IS A COSMIC COINCIDENCE ?!

~ m just now??

INFLATION* : tot = 1

* Phase change @T 10-35s with x 1050 flat space

tot FROM GEOMETRY OF THE UNIVERSE

WMAP 2001

Image of early Universe imprinted on temp. anisotropy of CMB

300 ky after BB photons decouple from matter T 6000 K

T/T 10-5

THE ANISOTROPY OF THE COSMIC MW BACKGROUND

before decoupling: plasma oscill./ of photon-baryon “liquid” sound waves CMB: snap shot of sound waves when rad. decoupled Today light red shifted by 1/1000 3K Smallness of T/T visible Universe once causally connected Inflation!

Image of quantum fluctuation at 1019 GeV

Expansion in spherical harmonics of CMB temp. field

Multipole development angular scale l number of cycles in the sky = / l

lpeak = 200 / tot

lpeak = 197 6 (0.90)

Baryon density small: b

Curvature of Universe: tot

“Cosmic variance”

(only one Universe)

Angular diameter of the moon

WMAP RESULTS: Other :

tot = 1.02.02 Inflation : tot = 1

b = 0.04 0.004 BBN: b = 0.039

m = 0.27 0.04 clusters of galaxies, grav. lensing

hot x-ray gas : m = 0.3

= 0.73 0.04 SN1a –redshift : = 0.7

H0 = 714 km/sec/Mpc Hubble: H0 =72 4

km/sec/Mpc

T0= 13.7 0.02 Gyr Hubble: 11 Gyr

DM & DEVELOPMENT OF STRUCTURE

• BB creates DM + ord. Matter

• DM decouples early

• Clumps

• Ordinary matter flows in

• Galaxies form

• Galaxies trace DM distribution

DO GALAXIES TRACE THE DM DISTRIBUTION ?

COSMOS EVOLUTION SURVEY: (Jan. 2007)

- First large scale 3D reconstruction of DM distribution

-Hubble Space Telescope: largest picture mosaic ever 1.40 x 1.40

- Distance by red shifts: ESO VLT (Chile), Magellan (Chile), Subaru (Hawaii), CHT (Hawaii)

--X-ray mapping of gas in galaxies: XMM Newton

- 0.5 M background galaxies for DM reconstruction by gravitational lensing

Near infra red HST

DM > six times more abundant than ordinary matter

Growing clumpiness of DM & ordinary matter flowing in

3.5 By ago

5 By ago

6.5 By ago

3 slices of red shift

60 M Ly

100 M Ly

Growing clumpiness of DM & ordinary matter flowing in

Next: Large Synoptic Survey Telescope (2013)

8.4 m diameter mirror

30 Tbyte/night

Google participates in organizing data analysis (New Scientist Jan. 2007)

SLOAN DIGITAL SKY SURVEY

- SDSS I completed Jan. 2005

- SDSS II until 2008

- maps cube of 6x109 Ly sides

WHAT IS THE STRUCTURE AT LARGE SCALE

Baryonic matter @T=225s (BBN) cannot clump to form voids (200MLy) filaments & superclusters

…structures thinned out by Hubble expansion

Assume DM decouples earlier @ T < TBBN and interacts weakly

• longer time to develop structure

• clumps earlier

• baryons fall into troughs

WHAT KIND OF MATTER CAN EXPLAIN LSS?

• galaxy formation

• Large scale structure

• Dark Matter

3 problems solved:

LARGE SCALE STRUCTURE & DM SPEED

HOT DM

COLD DM

• relativistic• e.g. massive ’s• before decoupling structures washed out• superclusters form first

• non relativistic• extremely weak interaction w. baryonic matter• clump on small scale• bottom-up model

• galax. in correct mass range (10-3 < MW < 104)

(ruled out by WMAP)

cdm-hdm1-princeton.mpeg

LARGE SCALE STRUCTURE

k

kikx kPek

xx

2)()(

)()(

The larger the scale we average the more uniform becomes the Universe!

Best fit:

b=5%

dm=25%

=70%

85% of gravitationally bound matter is non-baryonic !

Density of luminous matter 1% !

THE WHOLE PICTURE!