challenges for the standard cosmology tom shanks durham university
TRANSCRIPT
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?