Recent Topics on Observational
Cosmology
Naoshi Sugiyama
Division of Theoretical Astrophysics
National Astronomical Observatory, Japan
1. Introduction
2. Cosmological Parameters
3. Dark Matter
4. Structure Formation
5. Success of -CDM
§1.Introduction
-Observational CosmologyObserve the features of the present and past Universe
•Contents
baryon, electron, photon, neutrino
dark matter = unknown particles?, MACHO?
•Cosmological Parameter
, H0, q0, , age  dynamics
•Structure
galaxies, cluster of galaxies, Large Scale Structure
Cosmic Microwave Background

Extrapolate to the early Universe &
future Universe
•How was the Universe formed?
•What is the final fate of the Universe?
From the beginning to the end of the
Universe based on observations
§2.Cosmological Parameters
(1)Hubble Constant H0
Observations by HST key project
must determine distance to measure H0
Cepheid Variables by HST
calibrate 0-point of various methods < 25Mpc, 27gal
(1) Tully-Fisher relation for spiral galaxies
rotational vel. v vs absolute luminosity L
v = 220(L/L*)0.22 km/s
line width W
Sakai et al.
astro-ph/
9909269
(2) Fundamental plane of elliptical galaxies
velocity dispersion , radius r, surface brightness I
r   1.33 i -0.83
Oegerle & Hoessel 91
(3) Super Nova(SN)
light curve shape vs abs. luminosity
(4) Surface Brightness Fluctuations
flux: I=Nf (N: # of stars, f: flux of a star)
fluctuation: =N1/2f
2/I=f L/d (L:luminosity, d:distance)
Combine (Mould ApJ. 529 (00)786)
Riess, Press, Kirshner ApJ.473(96)88
Cephaid distance
HST Key
Project
Ferrarese et
al.
astro-ph
/9909134
Tully-Fisher: red, SNIa: green, SBF: blue,
Fundamental plane: cyan Ferrares et al. astro-ph/9909134
H 0  72  8km/s/Mpc
Freedman et al. ApJ, astro-ph/0012376
The biggest uncertainty is from distance to LMC
=> determine the 0 point of Cepheide
They assume
dLMC=50±3kpc
Other estimator of Cepheid 0 point
NGC 4258
7.2±0.3Mpc: orbital motion of disk
Herrnstein et al. Nature 400, 539 (99)
8.1±0.4Mpc: Cepheid
Maoz et al. Nature 401, 351 (99)
=> Cepheid has 12% error?
dLMC=44kpc? H0=80km/s/Mpc?
The devil is in the distance
©Bohdan Paczynski
(2)Cosmic Age t0
Cosmic Age Crisis?
t0=2/3H0=8.1(0.8/h)Gyr. for M =1, =0
=1/H0=12(0.8/h)Gyr. for M =0 , =0
H0=100h[km/s/Mpc]
•measurement of cosmic age
HR diagram of Globular Cluster
t0 > tGC = 11 ±1.0±1.4Gyr Cassisi et al. A&AS134(1999)103
= 13 ±2Gyr Chaboyer, talk given in Feb. 2001
high metal
low metal
Cutoff in White Dwarf Luminosity Function
t0 > tdisk = 10.5 (+2.5-1.5) Oswalt et al.
Nature382(1996)692
Universe must be almost empty or
dominated by cosmological constant
(3)Cosmological Constant 
High z Super Novae Ia Search
d L  (1  z )[ z  (1  q0 ) z 2  ] / H 0
q0   M / 2   
q0 : deceleration parameter
luminosity distance
If we measure the distance to high z objects, we can
determine q0 or /3H02
Perlmutter et al. ApJ.517 (99) 565
42 galaxies 0.18<z<0.83
0.8M  0.6  0.2  0.1
Two Loopholes:
•evolution of SN Ia
Are SNe at z~1 same as at z=0?
•Extinction by dust
light from SN may suffer significant damping by
interstellar dust
Cosmology and these systematic can be
distinguished if once we see SNe at z>1
Riess et al. astro-ph/0104455
Discovory of SNIa at z~1.7
SN 1997ff: photometrical redshift of SN, z=1.70.1
Gal, z=1.650.15
M 1/3 2/3
SNAP(Supernova/Acceleration Probe)
2000 SNe/yr. 3yr. 0.1<z<1.7
(4)Curvature of the Universe K
MK=1 (Friedmann eq.)
K-K/(a0 H0)2
CMB anisotropies
Measure the Last Scattering Surface (LSS)
(z=1000)
Projection from size on LSS to angle
•Observable quantites: Cl
angular power spectrum
l: multipole 1/
•Peak location of Cl :
corresponds to sound horizon
Flat Universe
Open Universe
三角形の内角の和180度
Last Scattering
内角の和＜180度


Observer
Observer
Closed Universe
内角の和＞180度
l1/

Observer
Peak shifts to larger l (open)
smaller l (closed)
Large Scale
Small scale
Not only curvature BUT also
• Bh2
• Mh2
• n (initial power law index)
• T/S (tensor perturbation contribution)
• reionization after recombination
Boomerang(Balloon) caltech, USSB, Rome
•long duration balloon: over 10 days
altitude 35km, 1milion m3 balloon
multi band: 90, 150, 240, 400GHz
•bolometric detectors cooled to 0.3K
•high resolution: 18’, 10.5’, 14’, 13’
•high sensitivity: 140, 170, 210, 2700Ks1/2
•256hours data, 2.5% of sky
P.de Bernardls et al. Nature 404 (2000)955
A.Langee et al. astro-ph/0005004
•Peak location lpeak=197±6 (1 error)
c.f. 220 for adiabatic std =1 CDM
0.88< m+ <1.12
(95%CL)
6 parameters fit
m(0.05-2), (0-1),
h(0.5-0.8), n(0.8-1.3)
Bh2(0.013-0.025)
Flat CDM
with  (SNe Ia)
MAXIMA-I (Balloon) UCB, Minnesota
•balloon: 3 hours (2 orders worse)
•multi band: 150, 240, 410GHz
•bolometric detectors cooled to 0.1K (factor 3 better)
•high resolution: 10’
•high sensitivity: 80Ks1/2 (factor 2 better)
Confirm BOOMERANG result
Jaffe et al.
Astro-
More data coming on April 2001
• Boomerang reanalysis (astro-ph/0104460)
• MAXIMA reanalysis (astro-ph/0104459)
• DASI: interferometer at south pole (astro-ph/0104489)
Consistent with Flat, BBN Bh2 (=0.022) CDM model
§3.Dark Matter
(1) Matter Density 0 (M)
重力的に測定する必要
光っている成分： ＊= 0.004
Scaleによって違い： Large scaleほど大きい
(a) 銀河のflat rotation curve
flat rotation curve suggests the existence of
Dark Halo Component = Dark Matter
Begman, Broeils, Sanders MNRAS 249,523 (1991)
halo
disk
gas
(b) スケール依存性
N.Bhacall
astro-ph/9901076
(2) Baryon Density B
Big Bang Nucleosynthesis
•Takes place at T=1010 ~ 109K
•Function of baryon-photon number ratio
nB/n=2.68 10-8Bh2
これが大きいと反応早めに進む
 nがpへの崩壊が進んでいなかった
 nが増え、結果4Heの量が増える
D, 3Heは燃えかすなので、少なくなってしまう
Review: Tytler et al. astro-ph/0001318
反応の時間発展
h=0.65
Bh2 = 0.019±
0.0024(95%)
理論値と
観測値
DのLy-
Recent results of D-abundance
Pettini & Bowen astro-ph/0104474
QSO 2206-199
D/H=(1.65±0.35)10-5
very low value
3 Damped Lyman Alpha system (higher column
density) out of 6 measurements of D/H
D/H=(2.2±0.2)10-5
Bh2 = 0.025±0.001(1)
B << M
Non-Baryonic Dark Matter の存在！
(3) Dark Matter の候補
（A)素粒子論的候補
粒子の持つ運動エネルギーで分類
a) Cold Dark Matter (CDM)
熱浴から早い時期に離脱し運動エネルギー小
候補粒子
• 最も軽い超対称粒子(LSP)
• axion
Weakly Interacting Massive Particles (WIMPs)
いまだかつて見つかっていない
b) Hot Dark Matter (HDM)
熱浴からの離脱遅く、運動エネルギー小
候補粒子
• 質量のあるニュートリノ
必要な質量はsuper-Kamiokandeの値より
はるかに大きい
  [3m / 93.84 eV]h
2
Super-Kはm2 ~ 10-3 eV2    103 h 2
CDMとHDMの違いは
宇宙の構造形成に大きく影響する
(B) 天体的候補
•BBNを満足させるにはPrimordial Black Holeのみ
•Haloの成分だけなら通常の天体でも可能？
Massive Compact Halo Object (MACHO)
(4) MACHO
The MACHO Project: Microlensing Results from 5.7
Years of LMC Observations :ApJ.542(2000)281
What they have done
•toward LMC: 5.7yr data
•1.19107stars13~17events
•variability of 34~230days
fit
amplification
What they have found
•expected from usual stars:2~4events
MACHO exist
0.4
7
•optical depth   1.2 0.3 10
1/2 compare to the previous result
•inconsistent with LMC/LMC-disk self lensing
•consistent with halos of Milky Way or LMC
•If they are halo events, MACHO is:
20% halo fraction for standard halo model
8~50% halo fraction with 95% CL
100% MACHO halo is ruled out with 95%CL
mass:0.15~0.9M
total 6~131010M within 50kpc
mass of MACHO
Fraction of MACHO
standard halo model
What is MACHO?
Perhaps White Dwarf (WD)!
•New cooling model of WD Hansen ApJ.520(99)680
much bluer than we thought if there is H-atmosphere

H2 provide strong opacity in infrared forcing the
radiation out in the blue
•We had been looking for wrong ones.
•In HDF, faint blue, fast moving object!
Ibata et al ApJ524 (1999)L95
He-atmosphere
1kpc
Hansen
H-atmosphere 2kpc
blue
red
MACHO is at most 50% of halo fraction
•MACHO=M is unlikely
If White Dwarf, the amount is constrained by
gamma-ray from distant sources (z=0.034)
Freese, et al. astro-ph/0002058
WD<(1-3)10-3h-1
Particle Dark Matter is still necessary!
§4. Structure Formation
Interaction between components
CMB
photon
Thomson
gravity
Scatt
electron
dark matter
baryon gravity
dark halo of galaxy
stars,
galaxy
gas
large scale
structure
Two important epochs
•matter-radiation equality epoch
zeq=60000(h/0.5)2, 1012s, 104K
before: radiation dominant
after: matter dominant
•recombination
zeq=1300, 1013s, 103K
before: highly ionized
after: neutral, transparent
Evolution
1) Before Equality epoch
Inside sound horizon:
photon & baryon = tightly coupled
 acoustic oscillations
dark matter: minor component
 cannot evolve
2) After Equality epoch
Inside horizon:
dark matter: major component
 evolve by self-gravity
ln 
 DM
 DM
 Baryon
recomb
Jeans cross equality
ln(1/(1+z))
ln 
 DM
 DM
 Baryon
recomb
Jeans cross equality
ln(1/(1+z))
3) After Recombination
photon & baryon: decoupled
photon: free stream to us
 CMB
baryon: grow (catch up with dark matter)
 Large Scale Structure
ln 
 DM
 DM
 Baryon
recomb
Jeans cross equality
ln(1/(1+z))
ln 
 DM
 DM
 Baryon
recomb
Jeans cross equality
ln(1/(1+z))
Dark Matter: equality epoch
CMB: recombination epoch
If dark matter has large kinetic energy:
small scale fluct are erased by random motion
Massive Neutrino: Hot Dark Matter
Specific Scale & Observational Quantities
•Matter Density Fluctuations
Horizon Scale at matter-radiation equality epoch
Power Spectrum P(k) k; wave number
Information
0h: horizon scale at matter-radiation equality epoch
measured in [h-1Mpc]
Initial Power Spectrum: very large scale
Nature of dark matter: cutoff on small scale
LSS cluster galaxies
P(k)
Horizon
at
equality
k
CDM
high 0h
CDM
k 3 ln k
low 0h
Initial
power HDM
high 0h
1
large scale
k[hMpc-1]
small scale
Observations
(1) Matter Density Fluctuations
Galaxy Redshift Survey
Past:
CfA, Las Campanas Redshift Survey, QDOT, …
on going and future:
2dF (100,000 galaxies out of 200,000),
Sloan Digital Sky Survey, 2MASS, DEEP,
PSCz,...
Shape of the power spectrum
0h=0.2-0.3 (Peacock & Dodds 1994)
if h=0.7 (HST), 00.3
Amplitude of the power spectrum
COBE normalization & Clusters
 low density (Eke et al 1996, Kitayama, Suto 1997)
low neutrino mass: m<0.6eV (Fukugita, Liu, NS 2000)
Eke, Cole,
Frenk 1996
2dF vs. APM
2dF (Peacock et al.)
2dF Galaxy Redshift Surevey
Mh=0.200.03, B/M=0.150.07
if h=0.7 (HST), 00.3
Peacock et al. astro-ph/0105500
Loop hole
bias: Do galaxies really trace the mass?
Direct measurement of underling gravitational field
Peculiar Velocity Field
Weak Gravitational Lensing
Weak gravitational lensing
Measuring cosmic shear field:
distortion of the galaxy images by lensing
Witteman et al.
Nature 405, 143 (00)

2
~  P(k )
1.2
M
~ 
1.2
M
2
8
References
Bacon D., Refregier A., Ellis. R., 2000, MNRAS, 318, 625
Kaiser N., Wilson G., Luppino G.~A., 2000, ApJ astro-ph/0003338
Maoli R., et al., 2001, A\&A, 368, 766
Van Waerbeke L., et al., 2000, A\&A, 358, 30
Van Waerbeke L., et al., 2001a, A\&A in press
Wittman D.~N., et al., 2000, Nature, 405, 143
Pirzkal et al., 2001, A&A in press, (astro-ph/0102330)
Van Waerbeke L., et al., 2001a, A\&A in press, astro-ph/0101511
Canada-France-Hawaii Telscpoe,
6.5 sq. deg. Field, ~40hours data
•
8 M0.6 =
+0.04
0.43 - 0.05
• M=0.3, =0.7, 8=0.9 CDM is consistent
M
§5.Success of -CDM
Low density adiabatic CDM:
0=0.3, =0.7, H0=70km/s/Mpc
succeed remarkably well
•distant SNe
•H0 from HST key project
•CMB anisotropies
•Cosmic Age
•Large Scale Structure of the Universe
matter power spectrum P(k):
shape parameter =0h=0.2~0.3
amplitude at 8h-1Mpc:8
•Is CDM real?
•What is CDM?
•Why and how does universe have ?
CDM is just a big trick
or reality?
5-1 CDM crisis on small scales?
CDM is still the most favorite dark matter candidate
BUT
Some modification is needed
Problems of CDM model:
structure formation on < 1Mpc
CDM predicts
• an overly dense core in the centers of gal and clusters
• an overly large number of halos within Local Group
• triaxial halos
Moore et al. ApJ Lett. 1998
High Resolution Simulations of CDM
  1/(r1.4(1+(r/rc)1.4) (Moore et al. ApJ.Lett 1998)
  r-1.4 in the center
Rotation Curve of galaxies
  1/(1+(r/rc)2) (de Blok & McGaugh MNRAS 1997)
  const. in the center
Klypin et al.
in 0.5h-1Mpc
ApJ 522(99)82
in 0.4h-1Mpc
Klypin et al.
ApJ 522(99)82
Self-interacting cold dark matter
(Spergel and Steinhardt PRL 84(2000)3760)
Consider
•self-interaction dark matter
•large scattering cross-section
•negligible annihilation or dissipation
•1kpc to 1Mpc mean free path
XX=8.110-25cm2 (mx/GeV)(Mpc/)
>1Mpc  no effect
<1kpc  too spherical cluster cores
Predictions:
(1)centers of halos are spherical
(2)dark matter halos have cores
(3)substructure in inner regions rapidly suppressed
Problems?
1) innermost regions of DM halos in massive clusters
are elliptical (Miralda-Escude astro-ph/0002050)
• gravitational lensing observations
XX<3.210-26cm2 (mx/GeV)
 >25Mpc: ruled out?
2) produce too large and too round cores
(Yoshida et al. astro-ph/0006134)
• numerical Simulations
Smaller
cross-section
triaxial/small core
Larger
cross-section
round/large core
3) too small velocity dispersion of Elliptical Galaxies
(Gnedin & Ostriker astro-ph/0010436)
4) appropriate particle candidates?
Particles with a conserver global charge (hidden
baryon number?) interacting through a hidden
gauge group (hidden color?)
Warm Dark Matter (WDM)
keV mass particles ~ cutoff at Mpc scale
RC  0.2( X h 2 / 0.15)0.15 ( g X / 1.5) 0.29 (mX / 1keV) 1.15 Mpc
Colin et al. ApJ 542(2000)622
Bode, Ostriker, Turok, astro-ph/0010389
Problem: hard to form small objects
• reionization before z>5: mX > 1.2keV
• Ly-alpha Forest: mX > 750eV
Barkana, Haiman, Ostriker astro-ph/0102304
Narayanan et al. astro-ph/0005095
5-2 Dark Energy
What is ?
Quintessence (Steinhardt et al.)
Motivation:
avoid fine tuning problem of 
•5th element:,baryon, dark matter, 
•Scalar Field works as an effective 
Should be: w=p/<0 (=-1 for )
=(dQ/dt)2/2+V(Q)
p=(dQ/dt)2/2-V(Q)
=>slow evolution of Q field
Naturalness requires
• as if radiation before matter-radiation euality
•attractor solution
Zlatev et al.
PRL82(1888)
896
Influence on Cosmology
= a-3(1+w)
works as “weak” 
•effects on CMB anisotropies:
change the matter-radiation equality epoch
•Constraint from high z SNe
modify the acceleration/deceleration
We have hope to determine the equation of state
w by SNe (at z~1) and/or CMB (z~1000)

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