“Dark Matter in Modern Cosmology”

1. “Dark Matter in Modern Cosmology” Sergio Colafrancesco

2. Summary Introduction Hystorical background and gained evidence Dark Matter candidates Motivations Dark Matter probes Types of probes Analysis of neutralino annihilations Future of Dark Matter Problems in DM probes Multi-approch of DM problem The alternative approch:modified gravity

3. Close to the plane of the Galaxy Dominating mass component Large structures Baryonic Low amount Introduction Dark Matter Scientific revolution DM Global Local

4. Hystorical background and gained evidence Radial velocities of galaxies in Coma cluster Zwicky (1933) Unexpected large velocity dispersion (бv) Mean density ~ 400 times greater Huge amount of “Dunkle Kalte Materie” (Cold Dark Matter) The problem

5. Smith (1936) Mass of Virgo cluster Unexpected high mass Excess of mass “Great mass of internebular material within the cluster” Babcock(1939) Spectra of M31 High mass to light ratio in the periphery Unexpected high rotational velocity in the outer regions Strong dust absorption

6. Rotation and surface brightness of one edge-on SO galaxy (NGC3115) Oort(1940) “Distribution of mass in this system appears to bear almost no relation to that of light” Motion of the galaxy M31 and of the Milky Way Kahn & Woltjer(1959) M31 and the Galaxy started to move apart ~ 15Gyr ago The mass of the Local Group had to be greater than the sum of galaxies masses Missing mass in the form of hot gas (T~5•105 k)

7. Rotation curve of M31 Roberts & Whitehurst (1975) High mass to light ratio in the outermost regions(› 200) No Kleperian drop-off Missing mass exist in cosmologically significant amounts

8. Confirmation of the presence of unknown matter by indipendent sources (beginning of the 1980’s) Dynamics of galaxies and of stars within galaxies Mass determinations of galaxy clusters based on gravitational lensing X-ray studies of clusters of galaxies N-body simulations of large scale structure formation

9. Solution: Non-baryonic dominating DM component The CMB contribution First detection of the CMB (1965): relic emission coming from the epoch of recombination Theory of fluctuations to explain the formation of structures Expected amplitude of the baryonic density fluctuations at the epoch of recombination COBE(1992): the amplitude of the fluctuations appears to be lower than expected

10. Dark Matter candidates Neutrinos High velocities HOT DARK MATTER No galaxy can be formed Hypothetical non baryonic particles Low velocities COLD DARK MATTER

11. Dissipationless Collisionless Cold Fluid on galactic scales and above Must behave sufficiently classically to be confined on galactic scales Search of the nature of Cold Dark Matter Astro-particle connection Properties of CDM candidates Upper and lower bounds on the mass of the particle

12. Most important candidates Light DM Sterile neutrinos Neutralinos Lightest right-handed neutrino Lightest particle of the minimal supersymmetric extension of the Standard Model (MSSM)

13. Motivations Galaxy rotation curves Dwarf galaxy mass estimators Galaxy cluster mass estimators Lensing reconstruction of the gravitational potential of galaxy clusters and large scale structures Combination of global geometrical probes of the Universe(CMB) and distance measurements (Sne) Large scale structure simulations

14. Presence, the total amount and the spatial distribution of DM in the large scale structures Inference probes Dynamics of galaxies Hydrodynamics of hot intra-cluster gas Gravitational lensing distortion of background galaxies Nature and physical properties of DM particles Physical probes Astrophysical signals of annihilation or decay Wide range of frequencies Dark matter probes Types of probes

15. Analysis of neutralino annihilations Galaxy cluster Astrophysical laboratories: Dwarf spheroidal galaxies Focus Particle: neutralino (Mχ range: few GeV to a several hundreds of GeV ) mass у-ray emission Synchrotron radiation Neutralino annihilation SED Bremsstrahlung radiation Inverse Compton Scattering (ICS) composition Neutrinos cross section

16. A general view

17. General informations Annihilation rate: R = nC (r) <s > nC (r) = nC,0 g(r) Annihilation cross section: <s > Wide range of values (theoretical upper limit <s > < 10-22 (Mχ/TeV)-2 cm3/s)

18. Particles produced Depending on physical composition Annihilation χ-χ Quarks, leptons vector bosons and Higgs bosons Decay Secondary electrons and positrons Energy losses Spatial diffusion (relevant on galactic and sub-galactic scales)

19. SED Decay:p0 g+g Continuum spectrum Gamma rays emission: Bremsstrahlung and ICS of secondary e± Coma cluster:

20. Draco dwarf galaxy:

21. Synchrotron emission of secondary e± Radio emission: Diffuse radio emission Coma cluster:

22. ICS of CMB: from microwaves to gamma-ray Secondary e± up-scatter CMB photons that will redistribuite over a wide frequency range up to gamma-ray frequencies ICS of CMB: SZ effect from DM annihilation Secondary e± up-scatter CMB photons to higher frequecies producing a peculiar SZ effect

23. Heating: Secondary e± produced heat the intra-cluster gas by Coulomb collisions The radius of the region in which DM produce an excess heating increases with neutralino mass Neutralino annihilation in nearby DM clumps produce cosmic rays that diffuse away Cosmic rays:

24. Direct and indirect probes for DM have not yet given a definite answer Some of the anomalies are not easy to explain within canonical DM models Future of Dark Matter Problems in DM probes DM that has no standard model gauge interactions

25. Multi approach of DM problem The DM induced signals are expected to be confused or overcome by other astrophysical signals Multi - frequency Multi - messenger Multi - experiment Multi approach Ideal systems

26. The alternative approach:modified gravity Mismatch between the predicted gravitational field and the observed one When effective gravitational acceleration is around or below: a~10-7 cms-2 (weak gravitational field) Newtonian theory of gravity break down?