Non Baryonic Nature of Dark Matter 4 arguments MACHOs Where are the dark baryons? Phys 250-13 Non Baryonic 1
Map of the territory dark matter and energy clumped H 2? gas baryonic dust VMO? MACHOs Primordial Black Holes thermal nonbaryonic Quintessence exotic particles Other dimensions? non-thermal Light Neutrinos WIMPs Axions Wimpzillas Phys 250-13 Non Baryonic 2
Argument 1 1. Dark matter appears to be non-baryonic <= Effective vs. b Ω appears to be much higher than conventional primordial nucleosynthesis Not undermined by recent cosmic microwave background + Supernova results Independent of Inflation! 1 0.1 Vel Corr. b=1 Baryon Invent. Cluster Evol. Dipole b=1 Power spectrum Cosmological Tests Supernovae + CMBR Ω eff Primordial Nucleosynthesis 0.01 Phys 250-13 Non Baryonic 3 0.001 10 100 1000 1e+04 1e+05 1e+06 Scale (kpc)
Argument 2 2. We need non baryonic dark matter for structure formation Comparison of CMB T/T and large scale Order of magnitude of T/T is natural with non baryonic dark matter and adiabatic fluctuations! CDM Extrapolation flat universe ν only baryonic CMB at z 1000 Large scale structure Phys 250-13 Non Baryonic 4
Arguments 3-4 3. Implausible efficiency of hiding baryons e.g. Baryonic content of clusters: X-ray temperature + dimension => total mass X-ray luminosity + dimension => mass of baryons Baryonic fraction between 10 and 20% (h/.65) -1.5 If totally baryonic, we would need to hide >75% of baryons in MACHOs/black holes Dark baryons are probably still in ionized gas 36 ROSAT clusters S Ettori, A.C Fabian astro-ph/9901304 4. Massive Compact Halo Objects (MACHOs) do not appear to form the halo of our galaxy! Important news! Phys 250-13 Non Baryonic 5 A Copernican revolution in the making?
The basic idea you are here MACHOs Massive Compact Halo Objects Milky Way Degeneracy between mass, distance and velocity x L * * * * * * * * * Large Magellanic Cloud=LMC 3 main collaborations CfPA MACHO, EROS, OGLE + new groups and M31 Clear demonstration of microlensing ( x) x( L x) L dx t mx( L x) 2 v L Phys 250-13 Non Baryonic 6
MACHOs No small LMC/SMC duration events => Dark Matter Brown Dwarfs Puzzling long duration LMC events Degeneracy between velocity,distance and mass We do not know where the lenses are! Even if distributed as halo: MACHO Group result: fraction 20% 8% fraction 50% 95% CL Mass is 0.5 M sun : Stars! Old white dwarfs? Looking for them with HST (high proper motion). Ibata et al Astro-ph/0002138. 10%? Initial Mass Function? Also compatible with no MACHO and puffed up LMC <= tidal interactions with the Milky Way The few lenses whose positions are known are in the host galaxies, not in the halo! Long duration events (2) towards SMC Not enough events in SMC compared to LMC Basis for exclusion plot from EROS 2nd generation: EROS II, OGLE II, SuperMachos,Stellar Interferometric Mission Phys 250-13 Non Baryonic 7
What Dark Matter cannot be Non ionized gas Gunn Peterson Astr. Phys. J. 142(1965) 1633 No trough Totally ionized gas y parameter CMBR X ray extragalactic background Dust Infrared radiation H snowballs Would evaporate Very Massive Objects Very fast supernovae, large black holes gobbling up metals to prevent contamination IR DIRBE observations Phys 250-13 Non Baryonic 8
Where are the Dark Baryons? Accounting Fukugita, Hogan, Peebles: Astro-ph/9712020 Astroph. J (1998) z 0: missing a factor of 2 with respect to Nucleosynthesis Most uncertain High redshift: z 3 Phys 250-13 Non Baryonic 9 Estimation from absorption + UV ionizing flux from quasars+ correction for local density Which fasten recombination and decreases ionizing fraction
Warm Hot Gas Davé, Cen, Ostriker et al Astro-ph/0007217 4 phases - diffuse δ<1000 T<10 5 K - condensed δ>1000 T<10 5 K - Hot T>10 7 K - Warm-Hot 10 5 K <T<10 7 K Heated by shocks. Low density contrast δ 30 around dense objects, filaments Falling Evolution of temperature understood Similar for different simulations 30-40% at low redshift Depends on resolution Cooling α ρ 2 feedback Parallel Tree Smooth Particle Hydrodynamics Contrary to previous estimates (e.g. Wu,Fabian,Nusser 1999, Pen 1999) compatible with the soft x-ray extragalactic background Previous authors where assuming virialization Phys 250-13 Non Baryonic 10
Detection of the Hot Warm gas Very challenging Emission May have been detected by ROSAT Wang& McCray : T 2x10 6 K Correlation with galaxies Soltan et al 96 Filaments Scharf et al Excellent prospect for XMM: imaging of filament CHANDRA? Absorption in cooler regions e.g. O VI in UV (STIS HST) 10% 50% e.g. Tripp and Savage Astrophys J. 542 (2000) Astro-ph/0004135 90% Phys 250-13 Non Baryonic 11