Challenges for the Standard Cosmology

Tom Shanks

Durham University

New Age of Precision Cosmology?

• 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

• Observed QSO P(k) agrees with CDM Mock QSO Catalogue from Hubble Volume

• Outram et al 2003

500h-1Mpc 50h-1Mpc

CDM Input Spectrum

Hubble Volume 1

And yet…….

Astrophysical Problems for CDM

• 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 sub-haloes (Moore et al, 1999b)

• Observed galaxy LF is much flatter than predicted by CDM - even with feedback (Cole et al, 1999).

• CDMMassive 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

• 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!

(from Benson et al 2003)

CDM haloes

No evolution seen for z<1 early-types

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.

Wake et al (2007)

Fundamental Problems for CDM CDM requires 2 pieces of undiscovered physics!!!

• makes model complicated+fine-tuned• 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• Optimists like search for neutrino!• Pessimists like search for E-M ether!

Fundamental Problems for CDM

• Even without , CDM model has fine tuning since CDM ~ baryon (Peebles 1985)

• Baryonic Dark Matter needed anyway!• Nucleosynthesis baryon ~ 10 x star

• Also Coma DM has significant baryon component

Coma cluster dark matter

Coma galaxy cluster gas

• 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

• X-Ray gas becomes Missing Mass in Coma. In central r<1h-1Mpc:-

Virial Mass 61014h-1Mo

Mvir/MX =15h1.5

X-ray Gas Mass 41013h-

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:

• X-ray gas becomes Dark Matter in Coma

• Inflationary baryon=1 model in better agreement with nucleosynthesis

• Light element abundances baryonh2<0.06• baryon 1 starts to be allowed if h0.3

• Inflation+EdS => =1 => Globular Cluster Ages of 13-16Gyr require Ho<40kms-1Mpc-1

• But the first acoustic peak is at l=330, not l=220

Escape routes from CDM

• 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• Strong anti-

correlation 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(But see Hoekstra et al 2003)

QSO-group/galaxy lensing

Myers et al 2003, 2005, Mountrichas & Shanks 2007

CMB Lensing - CDM

• Lensing smoothing functions computed for various models including standard CDM model - linear and non-linear (Seljak 1996)

CMB Lensing - CDM

• 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

• CMB lensing smoothing functions, ()/

• Only one that improves WMAP fit is ()=constant (black line)

• Requires massr-3 or steeper

• Also requires anti-bias at b~0.2 level

Foregrounds move 1st peak • 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!

WMAP SZat 94GHz

Bielby + Shanks 2007astro-ph/ 0703407

Lieu et al 2006, ApJ,648, L176

Z=0.02 Z~0.1

Z~0.2 Z~0.4

172 Abell Clusters

235 Abell Clusters 38 OVRO/BIMAClusters

Coma cluster

(arcmin)

T

Conclusions

• CDM gains strong support from WMAP, SNIa, P(k)

• But assumes “undiscovered physics” + very finely-tuned + 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?