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!