Chapter 12 Dark Matter - uni-wuppertal.deat-web.physik.uni-wuppertal.de/~kampert/Kosmologie... · Chapter 12 Dark Matter. Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007

Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007128

Chapter 12

Dark Matter


Baryonic Dark Matter

Brightness

Rotation Curve

expected from massassociated with light profile

measured

Brightness & Rotation Curve of NGC3198


NGC 7331

130

fit of major axis

observed radial velocities based onDoppler effect

rotation curve with individual contributions

astro-ph/9902240

Note: Here we assume applicability of Newtonian laws far beyondsolar system, i.e. the region of proven correctness.(Discussed alternative: MOdified Newtoanian Dynamics; MOND)


Gravitational Lens

131


Einstein Ring

132

Lensed Object (in background)

Lense in foreground


Einstein Ring

133


Microlensed LMC Objects

Sun

Massive Compact Halo Objects (MACHO)

light from some star in LMC

typically separated by milli-arc-sec

(not resolved)

But: amplification of light if images are not resolved:

t ! 100 days ·

√MMACHO

M!

up to ~ 0.75m


Observations

135

10 P. Tisserand et al.: Limits on the Macho content of the Galactic Halo from Eros-2

18.2

17.2

18.1

17.2

18.1 !0.5 1.0

200 2600

250 700

18.2

16

22

R

R

B

B

17.1

JD !2450000

R

(B!R)

17.1

eros

ero

s

EROS2!SMC!1sm0054m

R 18.14u0 0.52te 101.55t0 460.53

B 18.01u0 0.53te 105.85t0 458.95

5761

Fig. 6. The light curves of EROS-2 microlensing candidate EROS2-SMC-1 (star sm005-4m-5761). Also shown is the color-

magnitude diagram of the star’s CCD-quadrant and the excursion of the event.

18.5

15.5

19.5

15.5

19.5 !0.5

200 2600

2290 2410

18.5

15

21

(B!R)

R

R

B

B

16.5

16.5

JD!2450000

R

eros

ero

s

1.0

EROS2!LMC!15lm0570n

R 18.29u0 0.09te 27.51t0 2350.05

B 19.05u0 0.10te 27.50t0 2350.11

29305

Fig. 7. The light curves of EROS-2 star lm057-0n-29305 (r.a.= 79.9488 deg, dec.= !70.7741 deg). Also shown is the color-magnitude diagram of the star’s CCD-quadrant and the excursion of the event.

14 P. Tisserand et al.: Limits on the Macho content of the Galactic Halo from Eros-2

19.0

18.0

19.3

18.0

19.3 !0.5 1.0

200 2600

800 920

19.0

15

21

(B!R)

R

R

B

B

18.3

18.3

JD!2450000 eros

Rero

s

EROS1!LMC!1lm0582k

R 18.81u0 0.56te 26.60t0 858.90

B 19.03u0 0.56te 26.60t0 858.90

21915

Fig. 8. The EROS-2 light curve of EROS-1 microlensing candidate EROS1-LMC-1. The curve shows a second variation, 6.3

years after the variation observed in EROS-1. Also shown is the color-magnitude diagram of the star’s CCD-quadrant and the

excursion of the event.

20.3

18.3

20.7

18.3

20.7 !0.5 1.0

200 2600

2100 2350

20.3

15

21

(B!R)JD!2450000

R

R

B

B

18.7

18.7

eros

Rero

s

MACHO!LMC!23lm0553n

R 19.82u0 0.52te 55.70t0 2233.50

B 20.19u0 0.46te 61.10t0 2234.60

4994

Fig. 9. The EROS-2 light curve of MACHO microlensing candidate MACHO-LMC-23. The curve shows a second variation,

6.8 years after the variation seen by MACHO. Also shown is the color-magnitude diagram of the star’s CCD-quadrant and the

excursion of the event.

~ 140 days ~ 34 days

MACHOS as the major component of Galactic DM over 10-7 < MMACHO/MSun < 5 can be ruled out, i.e. fraction well below 10%

astr

o-ph

/060

7207


Intra-Cluster Gas

136

X-ray surveys of galaxy clusters allow also to estimate ΩM

Surface brightness ⇰ ρ, T profiles of Gas ⇰ Mass

Result: More matter contained in hot gas than in stars


Non-Baryonic DM

137

Expect ~ 0.25 Ωcrit

Classical candidate: Neutrinos (note: 350 νs / cm3 !)

If massive, could contribute significantly to DM

!! · h2 =!

i m!i

93 eV

t!3 He + !! + "̄e ⇰ mν < 2.05 eV

⇰ Ων < 0.07

Since mν is very small, velocity would be high, thus we call themHot Dark Matter (HDM)

Non-relativistic particles with masses in GeV scale are calledCold Dark Matter (CDM)


AXIONs

138

HDM candidate (light pseudoscalar particle; JP = 0-)(proposed because of absence of CP violation in strong interaction)

Weak interaction:τA ~ 1/mA5 > tUniverse for mA < 10 eV⇰ expect mA in range 10-6 - 10-3 eV/c2

⇰ expect abundance of 1012 - 1014 /cm3

May be observed by interaction with strong B-fields

γ-ray

B-field

AxionSun Axion LHC magnet + X-ray detect.

CAST experiment@ CERN


WIMPs

139

Weakly Interacting Massive Particle (generally preferred candidate)

May be detected directly by elastic WIMP-nucleus scattering; recoil of nucleus then detected by ionisation a/o by phonons

Highly sensitive semi-conductor counters may be used orbolometers at cryogenic temperatures (T < 1 K)

Erecoil =mT · mX

(mT + mX)2· mXv2(1! cos!) cV =

!Q

!T!

!T

!D

"3

mX mT

θ

example: V= 1 cm3 Si crystal;Erecoil = 6 keV ⇰ ΔT = 10-5 K; can be measured

!T =Erecoil

V · cV (T )

Basic Principles

A deposited energy E will produce a temperature rise !T:

!T =E

C(T )e"t

# , # =C(T )

G(T )

C(T) = heat capacity of absorberG(T)=thermal conductance link between the absorber and the reservoir at T0

T0

G(T)

Temperaturesensor

AbsorberC(T)

WIMP

E

Normal metals: the electronic part of C(T) ~ T, and dominates C at low T

Superconductors: the electronic part is ~ exp(-Tc/T), Tc = SC transition temperature

negligible compared to lattice contributions for T<<Tc


Direct detection techniques

ER

LightCharge

Phonons

ZEPLIN, XENONXMASS, WARP, ArDM

CRESSTCDMS EDELWEISS


WIMPs

141

Expected event rate R:

R = NT

!φ(E) · σ(E)dE

# of targetatoms

flux of DM particles

cross section

Typical rates: events/day/kg ~ 1 - 10-7

Thus, background is the problem !

Possible signature by velocityof Earth around Sun(seasonal modulation)

30 km/s


The DAMA experiment

At LNGS (3800 mwe)

9 x 9.7 kg low activity NaI crystals,

each viewed by 2 PMs (5-7 pe/keV)

QF on I: ~ 8%

background level: ~1-2 events/kg/d/keV

Ethreshold ! 2 keVe ! 25 keVr

End of data taking 2002

PSD: statistical analysis of

pulse time constant

=> limit from 1996

100 ns 500 ns

Nuclear recoils Electron recoils

PLB 509 (2001)


The DAMA Signal

Annual modulation analysis:

-> 7 annual cycles:

107800 kg x days

-> positive signal (6.3 ! CL)

Studied variations of:

T, P(N2), radon, noise,

energy scale, efficiencies,

n-background,

"-background

A cos [#(t-t0)]; t0 = 152.5 d; T = 1yr

Day 1 = Jan 1, 1995; A = 0.0192 +/- 0.0031 c/d/kg/keV

A = 0.0195 +/- 0.031 ev/d/kg/keVA = -0.0009 +/- 0.0019

ev/d/kg/keV

astro-ph/0307403,Riv. N. Cim. 26, 2003


CDMS detectors

Q inner

Q outer

A

B

D

C

Rbias

I bias

SQUID array Phonon D

Rfeedback

Vqbias

380! x 60! aluminum fins

(300 nm thick)

Absorber: 250 g Ge or 100 g Si crystal1 cm thick x 7.5 cm diameterT-sensor: photolithographic patterned thin Al+W films

Measure ionization in low-field (~volts/cm)

with segmentedcontacts to allow

rejection of events near outer edge

passive

tungsten

grid

4144 (4 x 1036) QETs

250 !m x 1 !m W(35 nm thick)


CDMS Background Discrimination

Use phonon risetime and charge to phonon delay for discrimination of surface events (’betas’)

surface events

gammas

neutrons

Ionization yield alone: ! Rejects >99.9% of gammas, >75% of ‘betas’

Ionization+phonon timing:! Rejects >99.9999% of gammas, >99% of ‘betas’

Ionization Yield

Phon

on d

elay

[µs]

Time [µs]

Ampl

itud

e

phonon delay


Where do we stand?

~ 0.2 event/kg/day

Most advanced experimentsstart to test the predicted SUSY parameter space

One evidence for a positive WIMP signal

Not confirmed by other experiments

1998

2006


!

WIMP capture in the sun

and annihilation in neutrinos

DETECT

n

"#

! + !! W + W ! " + "

Indirect Measurement

147

Preferred: Neutralino, the Lightest SUSY-particle


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Hints from Large Scale Structure

149

Hints from Large Scale Structure


Large Scale Structure: Simulations

150

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Chapter 12 Dark Matter - uni-wuppertal.deat-web.physik.uni-wuppertal.de/~kampert/Kosmologie... · Chapter 12 Dark Matter. Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007