Challenges for the Standard
Cosmology
Tom Shanks
Durham University
New Age of Precision Cosmology?
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Boomerang + WMAP CMB experiments
detect acoustic peak at l=220(≈1deg)
 Spatially flat, CDM Universe (de
Bernardis et al. 2000, Spergel et al 2003,
2006)
SNIa Hubble Diagram requires an
accelerating Universe with a  term
CDM also fits galaxy clustering power
spectrum (e.g. Cole et al 2005)
WMAP 3-Year CMB Map
WMAP 3-Year Power Spectrum
Universe comprises:
~72% Dark Energy
~24% CDM
~4% Baryons
(Hinshaw et al.
2003, 2006, Spergel
et al. 2003, 2006)
2dF QSO Power Spectrum
CDM Input Spectrum
Hubble Volume 1
500h-1Mpc
50h-1Mpc
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Observed QSO
P(k) agrees with
CDM Mock QSO
Catalogue from
Hubble Volume
Outram et al 2003
And yet…….
Astrophysical Problems for CDM
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Too much small scale power in mass distribution?
Mass profile of LSB galaxies less sharply peaked than
predicted by CDM (Moore et al, 1999a)
Instability of spiral disks to disruption by CDM subhaloes (Moore et al, 1999b)
Observed galaxy LF is much flatter than predicted by
CDM - even with feedback (Cole et al, 1999).
CDMMassive galaxies form late vs. “downsizing”
Slope of galaxy correlation function is flatter than
predicted by CDM mass  anti-bias  simple
high peaks bias disallowed (eg Cole et al, 1998)
LX-T relation  galaxy clusters not scale-free?
CDM Mass Function v Galaxy LF
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CDM haloes
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(from Benson et al 2003)
CDM halo mass
function is steeper
than faint galaxy LF
Various forms of
feedback are
invoked to try and
explain this issue
away
Gravitational
galaxy formation
theory becomes a
feedback theory!
No evolution seen for z<1 early-types
Wake et al
(2007)
Brown et al (2007)
Observe “downsizing” - but CDM predicts late epoch of galaxy
formation and hence strong dynamical evolution in the range 0<z<1.
Fundamental Problems for CDM
CDM requires 2 pieces of undiscovered physics!!!
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makes model complicated+fine-tuned
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 is small - after inflation, /rad ~ 1 in 10102
Also, today ~ Matter - Why?
To start with one fine tuning (flatness) problem and end
up with several - seems circular!
 anthropic principle ?!?
CDM Particle - No Laboratory Detection
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Optimists  like search for neutrino!
Pessimists like search for E-M ether!
Fundamental Problems for CDM
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Even without , CDM model has fine tuning since
CDM ~ baryon (Peebles 1985)
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Baryonic Dark Matter needed anyway!
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Nucleosynthesis  baryon ~ 10 x star
Also Coma DM has significant baryon component
Coma cluster dark matter
Coma galaxy cluster gas
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Coma contains hot
X-ray gas (~20%)
X-ray map of Coma
from XMM-Newton
(Briel et al 2001)
If M/L=5 then less
plausible to invoke
cosmological
density of exotic
particles than if
M/L=60-600!
H0 route to a simpler model
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X-Ray gas becomes Missing Mass in Coma.
In central r<1h-1Mpc:Virial Mass  61014h-1Mo
Mvir/MX =15h1.5
X-ray Gas Mass 41013h-2.5Mo
• Thus Mvir/MX=15 if h=1.0, 5 if h=0.5, 1.9 if h=0.25
3 Advantages of low H0
Shanks (1985) - if Ho<30kms-1Mpc-1 then:
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X-ray gas becomes Dark Matter in Coma
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Inflationary baryon=1 model in better agreement
with nucleosynthesis
• Light element abundances  baryonh2<0.06
• baryon 1 starts to be allowed if h0.3
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Inflation+EdS => =1 => Globular Cluster Ages of
13-16Gyr require Ho<40kms-1Mpc-1
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But the first acoustic peak is at l=330, not l=220
Escape routes from CDM
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Galaxy/QSO P(k) - scale dependent bias - abandon
the assumption that galaxies trace the mass!
SNIa Hubble Diagram - Evolution
WMAP - cosmic foregrounds?
• Epoch of Reionisation at z~10
• Galaxy Clusters - SZ inverse Compton
scattering of CMB
• Galaxy Clusters - lensing of CMB
The 2dF QSO Redshift Survey
23340 QSOs observed
2dF QSO Lensing
SDSS Galaxy Groups and Clusters in 2QZ NGC area
Strong QSO-group lensing
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(But see Hoekstra et al 2003)
Strong anticorrelation between
2dF QSOs and
foreground galaxy
groups (Myers et al
2003)
If caused by
lensing
magnification…
then high group
masses M ≈1
and/or anti-bias
b~0.2
QSO-group/galaxy lensing
Myers et al 2003, 2005, Mountrichas & Shanks 2007
CMB Lensing - CDM
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Lensing smoothing
functions computed
for various models
including standard
CDM model linear and nonlinear (Seljak 1996)
CMB Lensing - CDM
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Standard model
predicts only small
lensing effects on
CMB (Seljak, 1996)
But standard model
also predicts much
smaller lensing
effect than
observed with
confirmed 2QZ
QSOs……..
Implications for CMB Lensing
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CMB lensing
smoothing
functions, ()/
Only one that
improves WMAP fit
is ()=constant
(black line)
Requires massr-3
or steeper
Also requires antibias at b~0.2 level
Foregrounds move 1st peak
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WMAP z~10
Reionisation +
QSO lensing effects
of galaxies and
groups from Myers
et al (2003, 2005)
 l=330  l=220
Need SZ for 2nd
peak
 other models can
be fine-tuned to fit
WMAP first peak?
Shanks, 2007, MNRAS, 376, 173 (see also Lieu + Mittaz, 2005, ApJ, 628, 583)
SZ effect decreases with z!
T
WMAP SZ
at 94GHz
Z=0.02
Coma cluster
Z~0.1
172 Abell Clusters
(arcmin)
Lieu et al
2006, ApJ,
648, L176
Bielby +
Shanks 2007
astro-ph/
0703407
Z~0.2
235 Abell Clusters
Z~0.4
38 OVRO/BIMA
Clusters
Conclusions
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CDM gains strong support from WMAP, SNIa, P(k)
But assumes “undiscovered physics” + very finelytuned + problems in many other areas eg “downsizing”
To move to other models need to abandon assumption
that galaxies trace mass
QSO lensing  galaxy groups have more mass than
expected from virial theorem
Lensing (+reionisation) of CMB may give escape route
to simpler models than CDM
SZ CMB contamination - extended, z dependent?
Fine tuning CMB foregrounds - may allow Baryon =1,
low H0 model……plus others?