does dark matter really exist?
DESCRIPTION
Does dark matter really exist?. Benoit Famaey Oxford University 11.03.2005, FNRS contact group. DM in clusters DM in galaxies CDM cosmology Milky Way model MOND MOND in the MW Tully-Fisher relation. HSB & LSB galaxies Giant elliptical galaxies Baryonic DM in clusters? - PowerPoint PPT PresentationTRANSCRIPT
Does dark matter Does dark matter really exist?really exist?
Benoit FamaeyBenoit Famaey
Oxford UniversityOxford University
11.03.2005, FNRS contact group11.03.2005, FNRS contact group
OutlineOutline
I.I. DM in clustersDM in clusters
II.II. DM in galaxiesDM in galaxies
III.III. CDM cosmologyCDM cosmology
IV.IV. Milky Way modelMilky Way model
V.V. MONDMOND
VI.VI. MOND in the MWMOND in the MW
VII.VII. Tully-Fisher relationTully-Fisher relation
VIII.VIII. HSB & LSB galaxiesHSB & LSB galaxies
IX.IX. Giant elliptical Giant elliptical galaxiesgalaxies
X.X. Baryonic DM in Baryonic DM in clusters?clusters?
XI.XI. No-DM cosmology and No-DM cosmology and lensinglensing
XII.XII. Theoretical physicsTheoretical physics
XIII.XIII. ConclusionsConclusions
DM in galaxy clustersDM in galaxy clusters
1933 : Zwicky, Coma cluster1933 : Zwicky, Coma clusterK+U/2 = 0K+U/2 = 0with K ≈ 3M<vwith K ≈ 3M<v22
rr>/2>/2 and U ≈ -GM and U ≈ -GM22/(2 Mpc)/(2 Mpc) M/MM/Mvisvis ≈ 20 ≈ 20
Gravitational lensing: Gravitational lensing: i ≈ [4GM i ≈ [4GMclustercluster/c/c22 (d (dclustercluster
-1-1 - d - dsourcesource-1-1)])]1/21/2
DM in individual galaxiesDM in individual galaxies
VVcc(R) ≈ (GM(R)/R)(R) ≈ (GM(R)/R)1/21/2
VVcc ≈ cst ≈ cst M(R) M(R) R R (R) (R) R R-2-2
dark halo dark halo
NGC 3198NGC 3198
DM distribution from DM distribution from CDM cosmologyCDM cosmology
Supernovae data Supernovae data accelerating Universe accelerating Universe + WMAP + WMAP « concordance » « concordance » CDM modelCDM modelFlat Universe Flat Universe = 1 = 1
mattermatter = 0.3 and = 0.3 and = 0.7 = 0.7
Primordial nucleosynthesisPrimordial nucleosynthesis baryons baryons ≈ 0.04 ≈ 0.04 DM non-baryonic DM non-baryonic + cold (CDM) i.e. massive particles such as + cold (CDM) i.e. massive particles such as neutralino ~ 1 TeV to grow hierarchical neutralino ~ 1 TeV to grow hierarchical structure structure
High resolution simulations of High resolution simulations of clustering CDM halos clustering CDM halos (e.g. Diemand et al. (e.g. Diemand et al. 2004)2004)
Central cusp Central cusp r r--
with with > 1 > 1 Milky Way model Milky Way model (Klypin et al. 2002)(Klypin et al. 2002)
Milky Way model from gas dynamicsMilky Way model from gas dynamics
HI 21-cm (l,v) diagramsHI 21-cm (l,v) diagrams
Circular orbit at radius R:Circular orbit at radius R:
VVrr = [V = [Vcc(R)/R - V(R)/R - Vcc(R(R00)/R)/R00] R] R0 0 sin lsin l
Enveloppe: terminal velocity curveEnveloppe: terminal velocity curve
VVrr = sign(l) V = sign(l) Vcc(R(R00sin l) - Vsin l) - Vcc(R(R00) sin l) sin l
Bissantz et al. (2003)Bissantz et al. (2003) : potential from : potential from COBE near-IR luminosity density including COBE near-IR luminosity density including bar and spiral structure in disk with bar and spiral structure in disk with spatially constant M/Lspatially constant M/L
Fit M/L and Ω in potentials of bar and of Fit M/L and Ω in potentials of bar and of spiral to gas dynamicsspiral to gas dynamics
Provides good fit to microlensingProvides good fit to microlensing
No DMNo DM Milky Way provides good fits to gas Milky Way provides good fits to gas dynamics and microlensing within 5 kpcdynamics and microlensing within 5 kpc
But VBut Vcc(R(R00) = 185 km/s instead of 220 km/s) = 185 km/s instead of 220 km/s
DM haloDM halo
= 1/2 V= 1/2 V∞∞22 ln(r ln(r22 + r + rcc
22))
Negligible contribution inside 5 kpcNegligible contribution inside 5 kpc
NOTNOT cuspy if cuspy if mass inside 5 kpc shifted from baryons to mass inside 5 kpc shifted from baryons to DM, non-circular motions in (l,v) vanish DM, non-circular motions in (l,v) vanish (even shallow halo smoothes bumps)(even shallow halo smoothes bumps)
MOND
Milgrom (1983) :
Works for a0 = 1.2 X 10-8 cm s-2 ≈ cH0/2π ≈ c(/3)1/2
Bekenstein-Milgrom equations
MOND in the Milky Way
Inside 5 kpc a>a0 MOND = Newton
Fhalo = Vc2/r (1+rc
2/r2)-1
If FMOND = Vc2 /r and
(x) = x/(1+x) Then FMOND - FNewton= Vc
2/r (1+Vc2/ra0)-1
At R0, Fhalo/(FMOND - Fnewton) = 0.95
(Famaey & Binney 2005)
Tully-Fisher relation
• Deep MOND regime – when (x)~x
• At large r always enter deep MOND
HSB & LSB galaxies
(Sanders & McGaugh 2002)
LSB:
HSB:
Giant elliptical galaxiesGiant elliptical galaxies
Radial velocities of Planetary Nebulae Radial velocities of Planetary Nebulae (Romanowsky et al. 2003) (Romanowsky et al. 2003) up to very large radii up to very large radii in NGC 821, NGC 3379 and NGC 4494in NGC 821, NGC 3379 and NGC 4494
Quasi-Keplerian fall !! Quasi-Keplerian fall !! Quasi no-DM, but merger of disks !!Quasi no-DM, but merger of disks !! Very high accelerations, very small Very high accelerations, very small
discrepancy in MOND discrepancy in MOND (Milgrom & Sanders (Milgrom & Sanders 2003)2003)
Baryonic DM in clusters Baryonic DM in clusters of galaxies?of galaxies?
MOND predicts that baryonic matter has to be found in the cores
(ok since visiblevisible<< baryons)baryons)
No-DM cosmology and No-DM cosmology and lensinglensing
Needs relativistic Needs relativistic theory of MONDtheory of MOND
Early Universe not in Early Universe not in MOND regime if MOND regime if aa00=cst =cst
Results for CMB of Results for CMB of McGaugh (1999)McGaugh (1999) confirmed by WMAP confirmed by WMAP (McGaugh 2004)(McGaugh 2004)
Gravitational lensing: Gravitational lensing: GR implies strong GR implies strong correlation between correlation between visible and DM visible and DM distributions in lenses distributions in lenses
Kochanek (2002)Kochanek (2002) argued in favour of argued in favour of modified gravitymodified gravity
Theoretical physicsTheoretical physics Conformal gravityConformal gravity
(Mannheim & Kazanas 1989, (Mannheim & Kazanas 1989, Edery et al. 2003)Edery et al. 2003)
FFtot tot = F + = F + 00cc22/2/2No dark energyNo dark energyNot exactly MONDNot exactly MOND
Less deflection for null Less deflection for null geodesicsgeodesics
Nonsymmetric gravityNonsymmetric gravity (Moffat 2004)(Moffat 2004)
gg = g = g(()) + g + g[[]] Non-abelian effectsNon-abelian effects of of
quantum gravity inspired quantum gravity inspired from QCD from QCD (Deur 2003)(Deur 2003)
Relational gravityRelational gravity (Roscoe 2004)(Roscoe 2004)
Theory that does not Theory that does not accept empty space-accept empty space-time as a solutiontime as a solution
Effect of the vacuumEffect of the vacuum (Milgrom 1999)(Milgrom 1999)
in in -Universe, -Universe, has an has an effect on inertia at effect on inertia at accelerations ~ c accelerations ~ c 1/2 1/2
(~a(~a00)) TeVeSTeVeS (Bekenstein 2004)(Bekenstein 2004)
g’g’= e= e-2-2(g(g+U+UUU))-e-e22UUUU
ConclusionsConclusions
OROR GR is THE correct theory of gravitation GR is THE correct theory of gravitation
THEN dark matter must exist THEN dark matter must exist BUT strong coupling with visible matter BUT strong coupling with visible matter (Tully-Fisher, bumpy rotation curves, (Tully-Fisher, bumpy rotation curves, lack of DM in giant ellipticals, lensing…)lack of DM in giant ellipticals, lensing…)
detecting a neutralino detecting a neutralino end of the mystery ! end of the mystery !
OROR amazing observational successes of amazing observational successes of MOND are the peak of an iceberg, i.e. the MOND are the peak of an iceberg, i.e. the correct gravitational theorycorrect gravitational theory
Must make proper dynamical models of Must make proper dynamical models of galaxies within MOND (simulate spiral galaxies within MOND (simulate spiral structure) structure) + CMB, large-scale structure predictions, + CMB, large-scale structure predictions, gravitational waves astrophysics with gravitational waves astrophysics with relativistic theories such as TeVeSrelativistic theories such as TeVeS
See if we can also eliminate the “dark See if we can also eliminate the “dark energy” AND… energy” AND… understand the link with the rest of physics understand the link with the rest of physics (quantum gravity?)(quantum gravity?)