Post on 18-Sep-2018
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007128
Chapter 12
Dark Matter
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
Baryonic Dark Matter
Brightness
Rotation Curve
expected from massassociated with light profile
measured
Brightness & Rotation Curve of NGC3198
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
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)
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
Gravitational Lens
131
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
Einstein Ring
132
Lensed Object (in background)
Lense in foreground
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
Einstein Ring
133
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
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
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
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
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
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
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
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)
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
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
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
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
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
Direct detection techniques
ER
LightCharge
Phonons
ZEPLIN, XENONXMASS, WARP, ArDM
CRESSTCDMS EDELWEISS
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
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
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
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)
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
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
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
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)
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
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
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
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
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
!
WIMP capture in the sun
and annihilation in neutrinos
DETECT
n
"#
! + !! W + W ! " + "
Indirect Measurement
147
Preferred: Neutralino, the Lightest SUSY-particle
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
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Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
Hints from Large Scale Structure
149
Hints from Large Scale Structure
Karl-Heinz Kampert – Univ. Wuppertal Cosmology WS 2006/2007
Large Scale Structure: Simulations
150
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