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Colafrancesco - Dark Matter Dectection 1


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  • 1. CTICS 2012 Jan 24th, 2012Dark Matter detection (1)Sergio ColafrancescoWits University - DST/NRF SKA Research ChairINAF - OAREmail: 1
  • 2. Dark Matter exists !Dark Matter Proof Found,Scientists Say [F. Zwicky 1933]A team of researchers has found the first direct proof for theexistence of dark matter, the mysterious and almost invisiblesubstance thought to make up almost a quarter of the universe.In this composite image, two clusters of galaxies are seen after acollision. Hot gas, seen in red, was dragged away from thegalaxies during the collision. That gas makes up more than 90percent of the mass of normal, or visible, matter. But most of themass—and thus matter—is located in the galaxy portions of theclusters, shown in blue, scientists say. In other words, the bulk ofvisible matter in the clusters has been separated from the majority 2of mass—which therefore must be dark matter.
  • 3. Dark Matter exists ! … or not !?Dark Matter Proof Found, Dark matter does not exist !Scientists Say Einstein wins again! J. Moffat and colleagues suggest that there is a good reason dark matter why has never been [F. Zwicky 1933] directly detected: It doesnt exist .A team of researchers has found the first direct proof for the J. Moffat suggests that his Modified Gravityexistence of dark matter, the mysterious and almost invisible (MOG) theory can explain the Bullet Clustersubstance thought to make up almost a quarter of the universe. observation. MOG predicts that the force ofIn this composite image, two clusters of galaxies are seen after a gravity changes with distance.collision. Hot gas, seen in red, was dragged away from the Moffat thinks that the present day expectation bygalaxies during the collision. That gas makes up more than 90 many that dark matter must exist is similar to thepercent of the mass of normal, or visible, matter. But most of the expectation by many leading scientists in themass—and thus matter—is located in the galaxy portions of the beginning of the 20th century that aclusters, shown in blue, scientists say. In other words, the bulk of "luminiferous ether" should exist. This was avisible matter in the clusters has been separated from the majority hypothetical substance, in which the waves of 3of mass—which therefore must be dark matter. light were supposed to propagate
  • 4. Dark Matter Modified GFundamental Physics - Astronomy connectionGµν=8πG(TMµν+TDMµν+ΤDEµν) F(gµν)+Gµν=8pG TMµν 3 GM  exp(− r / L)  Φ (r ) = −  1 +  4a1 R 3 4
  • 5. Multi-wavelengthMulti-messenger Multi-experiments 5
  • 6. Multi-wavelengthMulti-epoch Multi-scaleMulti-messenger Multi-experiments 6
  • 7. Outline Multi-epoch The Dark Matter Timeline The present Multi-Scale + M3 Galactic center Galactic structures Galaxy Clusters The Future The DM search challenge 7
  • 8. Outline Multi-epoch The Dark Matter Timeline The present Multi-Scale + M3 DM search at various astronomical scales • Galactic center • Galactic structures • Galaxy Clusters The Future The DM search challenge 8
  • 9. Dark Matter timeline 2T + U = 0 Coma σ V ≈ (1019 ± 360)km / s M ≈ 400 ⋅ h558 L Zwicky used the words “dunkle (kalte) Materie” dark (cold) Matter which might be regarded as the first reference to Fritz Zwicky Cold Dark Matter[Varna (Bulgaria), 1898 – Pasadena (USA), 1974] … even though not in the modern sense (!?) 9
  • 10. Dark Matter timeline1936 - Smith noticed that 1939 - Babcock noticed that thealso the Virgo cluster exhibited outer regions of M31 were rotatinga behavior suggestive of an with an unexpectedly high velocityextremely high mass. indicating a missing mass. 10
  • 11. Dark Matter timeline 1910’s Ernst Öpik & wife Grigory KuzminLocal Dark Matter Global Dark Matter Öpik (1915) Zwicky (1933) Oort (1932, 1960) Zwicky discovered what so many scientists find when Kuzmin (1952, 1955) probing the depths of the current and accepted knowledge of the times. Eelsalu (1959) What Zwicky uncovered was considered an anomaly. Jõeveer (1972, 1974) Zwicky, who did not particularly belong to the Bahcall (1985) astronomical community, was making a claim that could overthrow present knowledge of the universe. Gilmore et al (1989) It was not the right time for the astronomical community to accept such a revolutionary idea. 11
  • 12. Dark Matter timeline1959 - Kahn & Woltjer published their 1961 - The renaissance of Dark Matter truly begandiscovery of a missing mass in the Local with the Santa Barbara Conference on the Instability ofGroup (  hot gas with T ∼ 5·105 K ) Galaxies. GalaxiesInterestingly enough, they did not cite By this time, enough research was done for theZwicky’s (1933) paper. community to see that the missing mass anomaly was not going to go away. “When... an anomaly comes to seem more than just another puzzle of normal science, the transition to crisis and to extraordinary science has begun” (Kuhn). Vera Rubin working at the Ford spectrograph (1955) 12
  • 13. Dark Matter timeline 1980 - Experimental results on the neutrino rest mass wereJim Peebles explains the secrets of galaxy formation Scott Tremaine (Tallinn 1977)1975 – By this time the majority of astronomershad become convinced that missing mass existed incosmologically significant amounts.Uncertainty on the Dark Matter nature remained !!!1977 – Rees speculated that “there are otherpossibilities of more exotic character – for instancethe idea of neutrinos with small (∼few eV) rest mass” Zel’dovich & Longair (Tallinn 1977) 13
  • 14. Dark Matter timelineA high-resolution CDM simulation with small-scale structure1980’s – The Cold Dark Matter model withaxions or other weakly interactive particles WIMPwas as an alternative to neutrino models (providingthe Hot Dark Matter). 14
  • 15. Dark Matter timeline J. Soldner 1804 A. Einstein 1911 1990’s – Dark Matter distribution in clusters can explain the gravitational lensing of background galaxies. 15
  • 16. False Alarms & Diversionary ManouvresJ. Oort (1960, 1965) believed that he had found somedynamical evidence for the presence of missing mass inthe disk of the Galaxy. If true, this would have indicatedthat some of the DM was dissipative in nature. However, 1987 – One particularly interesting dissenter:late in his life, Oort confessed that the existence of M.Milgrom. He believed that the existence of the DMmissing mass in the Galactic plane was never one of his implied that Newton’s law of gravity must be amendedmost firmly held scientific beliefs. Detailed observations, for gravitational accelerations that are very small, such(reviewed by Tinney 1999), show that brown dwarfs as the gravitational accelerations seen in a galaxy’scannot make a significant contribution to the density of outer fringes. the Galactic disk near the Sun. Bekenstein followed up Milgrom’s idea in TeVeS model 16
  • 17. Dark Matter timeline 1992-99 – Dark Matter is a main ingredient of the cosmic fluid and its effect is present in the CMB anisotropy spectrum . 17
  • 18. Dark Matter timeline 1990-2000 – Naissance of Astroparticle – Dark Matter physical connection. 18
  • 19. The Dark Matter Scenario: timeline 2010 Missing mass Rotation N-body simulations Lensing CMB Cosmology Astronomy Dynamics curves 1977 Thermal relicsParticle Astro Particle (Lee & Weinberg) TodayPhysics Physics 1984 Indirect DM search idea ν - mass (SIlk Beyond the SM & Srednicki) !? theo. & exp. 1985 SUSY DirectSUSY DM experiments AXION (Goodman & Witten) Sterile ν ∆ m 2ν 19
  • 20. The Present“The Present and the bubbles of Time" - Oil and acrylic on thin cardboard (B. D’Aleppo) 20
  • 21. Dark Matter Scenario: motivations WMAP 21
  • 22. DM & CMBGeneric ΛCDM WMAP 7yr h 2Ω DM = 0.1123 ± 0.0035 0.222 ≤ Ω DM ≤ 0.236 22
  • 23. DM distribution in cosmic time Dark Matter grows increasingly clumpy as it collapses under gravity. The map stretches halfway back to the beginning of the universe 23
  • 24. DM relic density n σV ≈ H x WIMPsin thermal equilibrium 3 ⋅ 10 − 27 cm − 3 s − 1 Freeze-out Ω χ h ≈ 2 σV A 24
  • 25. Formation of DM halos 25
  • 26. DM: the most palpable proof 26
  • 27. DM: the most palpable proof 27
  • 28. DM properties: 5 basic Very weak e.m. interactions Dissipationless no radiative coolingDark Matter DM self-interaction only at No constraint on the Collisionless high ρ and short relative D space of possibilities MX > 1 keV thermal Cold MX smaller non-thermal No DM discreteness Fluid on galactic scales Upper bound M X ≤ 10 70 − 71 eV DM confined Classical on galactic scales Lower bound M χ ≥ 10 − 22 eV 28
  • 29. DM candidates “Fuzzy” CDM Lower possible end of CDM Bosons with M∼10-22 eV Chaplygin Gas DM-DE common origin P=-A/ρ Non-thermal production Axions µ eV < Maxion < m eV Experimental limits NeutrinosDark Matter Warm DM 0.0005 < Ων h2< 0.0076 Massive neutrinos acceptable Sterile ν with mν ∼ 10-100 keV Light (MeV) DM Spin = 0 supersymmetric particle Gravitinos 1 MeV < MLDM < 4 MeV SUSY DM Elusive: only e± 511 keV line Neutralinos Neutralinos Kaluza-Klein excitations Extra dimension L-KK (r-parity) particle: stable Sneutrinos MKK ∼1 TeV Axinos Branons String theory brane fluctuations Mbranon > 100 GeV Q-balls Mirror Matter Ordinary matter in mirror world Split-SUSY Dissipative & complex chemics MWIMP WIMPzillas Produced at the end of Inflation M > 1013 GeV PBHs BHs @ quark-hadron transition MPBH ∼Mhorizon(T=102MeV) > M 29
  • 30. Viable DM candidates Neutralinos Light (MeV) DM Sterile ν’s Unstable 3 ⋅ 10 − 27 cm − 3 s − 1Ω χh ≈2 σV A Radiative decay: line0.09 ≤ ΩInDM h 2 ≤ 0.13 models, all Standard Model supersymmetry particles have partner particles with the same quantum numbers but spin differing by 1/2. Since ν → ν + γ s α the superpartners of the Z boson (zino), the photon (photino) and the neutral higgs (higgsino) have the same quantum numbers, they can mix to form four eigenstates of the mass operator called "neutralinos". In many models the lightest of the four neutralinos turns out to be the lightest supersymmetric particle (LSP). 30
  • 31. Viable DM candidates Neutralinos Light (MeV) DM Sterile ν’s Unstable 3 ⋅ 10 − 27 cm − 3 s − 1Ω χh ≈2 σV A Radiative decay: lineScalar ≤ (spin=0)2 ≤ 0.13 may be DM candidates, provided they annihilate 0.09 Ω DM h particlessufficiently strongly through new interactions, such as those induced by a newlight neutral spin-1 boson U. The corresponding interaction is stronger than weak νs → να + γinteractions at lower energies, but weaker at higher energies. Annihilation crosssections of (axially coupled ) spin-1/2 DM particles, induced by a U vectoriallycoupled to matter, are the same as for spin-0 particles. In both cases, the crosssections (σannVrel/c) into e+e− automatically include a v2dm suppression factor,needed to avoid an excessive production of γ-rays from residual DM annihilations.Spin-0 DM particles annihilating into e+e− have been claimed to be responsible forthe bright 511 keV γ-ray line observed by INTEGRAL from the galactic bulge. 31
  • 32. Viable DM candidates Neutralinos Light (MeV) DM Sterile ν’s Unstable 3 ⋅ 10 − 27 cm − 3 s − 1 Ω χh ≈ 2The term sterile A neutrino was coined by Bruno σV DecayPontecorvo who hypothesized the existence of the 0.09 ≤ Ω DM h 2 ≤ 0.13right-handed neutrinos in a seminal paper (1967), inwhich he also considered vacuum neutrino oscillationsin the laboratory and in astrophysics, the leptonnumber violation, the neutrinoless double beta decay,some rare processes, such as μ → e γ, and several Radiative decay: lineother questions that have dominated the neutrino ν s → να + γphysics for the next four decades. Most models of theneutrino masses introduce sterile (or right-handed)neutrinos to generate the masses of the ordinaryneutrinos via the seesaw mechanism. 32
  • 33. Viable DM candidatesNeutralinos Light (MeV) DM Sterile ν’s M a lD Unstable g ic olo Radiative decay: line sm Co o N νs → να + γ Excluded by BBN WMAP (95%) SNe Excluded by BBN e- anomalous magnetic moment Bremsstrahlung in-flight annihilation 33
  • 34. Hunt for the DM particleDM exists: we feel its (gravitational) presenceDM is mostly non-baryonic: we must think of a specific search strategyDM is very elusive: we must consider un-ambiguous evidence Crucial Probes are required ! 34
  • 35. Dark Matter probes Above-the-ground Under-ground 35
  • 36. DM direct searchχ δ = 30o vsun= 230 km/s χ vorb = 30 km/s Elastic interaction on nucleus, typical χ velocity ~ 250 km/s χ χ ER ~ 10-30 keV 36
  • 37. DM direct search 37
  • 38. The first hint There is evidence for a modulation in the DAMA data at 8.2 σ. Compatible with what would beGran Sasso (Italy) expected from some dark matter particles in some galactic halo models. 38
  • 39. Some of the latest results: CDMS II 2 events in the observed signal region. Based on background estimate, the probability of observing two or more background events is ~23%.Ahmed et al. arXiv:0912.3592v1 39
  • 40. Some of the latest results: CoGeNT 40
  • 41. Some of the recent results: CRESST-II [arXiv:1109.0702] 41
  • 42. DM direct search: criticalitiesExperimental techniques Astrophysics Effect of substructures Assume a local DM density on the local DM density and a DM halo structure [Kamionkowski & Koushiappas 2008] 42
  • 43. DM search @ accelerators“Well, either we’ve found the Higgs boson,or Fred’s just put the kettle on.”  CERN - Geneva 43
  • 44. LHC vs. direct detection experimentsAccelerator searches for DM are particularly promising …but even if WIMPs are found at the Large Hadron Collider(LHC), it will be difficult to prove that they constitute the bulkof the DM in the Universe. 44
  • 45. DM - Astrophysical probes INFERENCE PHYSICAL + +Virial Theorem Annihilation DecayHydro Equilibrium X+ X→ π 0, ± , p,... X → xi + γGravitational lensing X + X → e ± , µ ± ,τ ± ,ν i 45
  • 46. DM - Astrophysical search INFERENCE PHYSICAL AL UCI AL R I T C R UC + NO CVulnerable against: Virial TheoremMOND: Modified Newtonian Dynamics Annihilation Decay Testable against:TeVeS : Tensor-Vector-Scalar Hydro Equilibrium X + X → π 0, ± , p,... X → xi + γOrdinary matter feels a transformed metric Electromagnetic signals Gravitational lensing X + X → e ± , µ ± ,τ ± ,ν i DM illuminates thru its interaction 46
  • 47. DM - Astrophysical searchClean and unbiased location in the sky  Best Astrophysical LaboratoriesNO YESClear and specific SED in the e.m. spectrum  Most specific e.m. signals 47
  • 48. Viable DM candidates: signals Neutralinos Light (MeV) DM Sterile ν’s M Annihilating MeV DM a lD Radiative decay: line ic • Continuum: HXR/γ-rays νs → να + γ og • Line: e± annihilation ol sm Co o Ms N 511 keVInverse Compton scattering Bremsstrahlung π 0 MχSynchr. Bremsstrahlung 48
  • 49. Viable DM candidates: signalsNeutralinos Sterile ν’s Annihilation Radiative decay: line νs → να + γ Neutralino density profile ~ (nχ · nχ) ~ ρ2DM Sterile ν density profile ~ nχ ~ ρDM 49
  • 50. Viable DM candidates: signals Neutralinos Sterile ν’s Annihilation Radiative decay: line νs → να + γ DM annihilation flux DM decay flux 1 ρ DM ( r ) 2 1 ρ DM ( r )F ∝ 2 2 〈σ V 〉 Astro physics F ∝ 2 〈 Γ rad 〉 DL Mχ DL Mv  dE × [ f ann ( E ; χ )]  Particle physics [ ]  dE  × Eγ ( M v )    dν   dν  50
  • 51. Dark Matter halo structure 51
  • 52. DM halo profile: constraints Galaxies Galaxy Clusters• No evidence for a density cusp at r < 0.2 kpc• NGC2976: η =0.27 at r < 1.8 Kpc [Simon et al. 2003] η ! l. 2003] on alal et a η• Inner steeper profile ? s [D i nt tra [Gnedin & Primack 2003] NFW ons BH ? n oc [Sand et al. 2002] MS2137-23 Cluster η1T η2T A2029 0.5 2 NGC 6822 A1689 1.3 1.6 [Weldrake et al. 2002] A1835 0.9 1.1 MS1358 1.8 1.8 [Bautz & Arabadjis 2002] 52
  • 53. DM density universal profile Galaxies Clusters DwarfsNumerical simulations (CDM)Different groups obtained similar results[Navarro et al. 2003, Reed et al. 2003, …]Analytical fittingGeneral DM profile 53
  • 54. DM halo: smooth + clumps + BHsCluster of galaxies [CPU 2006] [Berezinsky et al. 2006] dSph Galaxy 54
  • 55. Imagine a …Galaxy Cluster of galaxies 55
  • 56. An astronomer’s viewGalaxy Cluster of galaxies 56
  • 57. A cosmologist’s viewGalaxy Cluster of galaxies 57
  • 58. An Astroparticle Physicist’s viewGalaxy Cluster of galaxies 58
  • 59. Theoretical description[Colafrancesco et al. 2006 A&A 455, 21–43] 59
  • 60. DM halo profileWe consider the limit in which the mean DM distributioncan be regarded as spherically symmetricand represented by the parametric radial density profile Two schemes are adopted to choose the function g(x) , with x=(r/a)Scheme 1Assume that g(x) can be directly inferred as the function setting the universalshape of DM halos found in numerical N-body simulations. We are assuming,hence, that the DM profile is essentially unaltered from the stage preceding thebaryon collapse, which is – strictly speaking – the picture provided by thesimulations for the present-day cluster morphology. [NFW 2004] [Diemand 2005] 60
  • 61. DM halo structureScheme 2 The other extreme scheme is a picture in which the baryon infall induces a large transfer of angular momentum between the luminous and the dark components of the cosmic structure, with significant modification of the shape of the DM profile in its inner region. Baryons might then sink in the central part of DM halos after getting clumped into dense gas clouds (see El-Zant et al. 2001), with the halo density profile in the final configuration found to be described by a profile with a large core radius (see, e.g., Burkert 1995):Once the shape of the DM profile is chosen, the radial density profile g(x)is fully specified by two parameters: i) length-scale a ii) normalization parameter ρ.It is useful to describe the density profile model by other two parameters:the virial mass Mvir and concentration parameter cvir. 61
  • 62. DM halo structureConcentration parameter We introduce the virial radius Rvir of a DM halo of mass Mvir as the radius within which the mean density of the halo is equal to the virial overdensity Δvir times the mean background density We assume that the virial overdensity can be approximated by an expression appropriate for a flat cosmology [Colafrancesco et al.’94,’97; Bryan & Norman ’98, …] The concentration parameter is then defined as with r−2 the radius at which the effective logarithmic slope of the DM profile is −2. • x−2 = 1 for the N04 profile • x−2 = 2−γ for D05 • x−2 = 1.52 for the Burkert profile 62
  • 63. DM halo structureSince the first numerical results with large statistics became available (Navarro etal. 1996, 1997), it has been realized that, at any given redshift, there is a strongcorrelation between cvir and Mvir, with larger concentrations found in lighter halos.This trend may be intuitively explained by the fact that mean overdensities in halosshould be correlated with the mean background densities at the time of collapse,and in the hierarchical structure formation model small objects form first, when theUniverse was indeed denser.The correlation between cvir and Mviris relevant at two levels:• when discussing the mean density profile• when including substructures[Bullock et al][ENS] 63
  • 64. DM Halo structureFor a given shape of the DM halo profile we fit of the parameters Mvir and cviragainst the available dynamical constraints for the Coma cluster.We consider bounds on the cluster total mass at large radii and on densityprofile in its inner region.• Redshift-space caustics (Geller 1999)• HE condition (Hughes 1989)• Velocity moments of a tracer population (Binney & Mamon 1982) [Colafrancesco et al. 2006 A&A 455, 21–43] 64
  • 65. DM Halo structure Sub-structuresρDM ρ2DM 65
  • 66. DM Halo structureTo discuss substructures in a cluster,analogously to the general picture introducedabove for DM halos, we label a subhalo through • virial mass Ms • concentration parameter cs.• The subhalo profile shape is considered here to be spherical and of the same form as for the parent halo.• The distribution of subhalos in a DM halo is taken to be spherically symmetric. symmetric 66
  • 67. DM Halo structureThe subhalo number density probability distribution can then be fully specifiedthrough Ms, cs and the radial coordinate for the subhalo position r. The sub-halo mas function is [Diemand 2005] A(Mvir) is derived imposingThe quantity Ps(cs) is a log-normal distribution in concentration parametersaround a mean value set by the substructure mass.The 1σ deviation Δ(log10 cs) around the mean in Ps(cs), is assumed to beindependent of Ms and of cosmology, and to be, numerically, Δ(log10 cs) = 0.14 ps(r) is the spatial distribution of substructures within the cluster. (with a’>a) and normalized as: 67
  • 68. DM annihilation distributionFor any stable particle species i, generated promptly in the annihilation orproduced in the decay and fragmentation processes of the annihilationyields, the source function Qi(r, E) gives the number of particles per unit time,energy and volume element produced locally in space:Npairs(r) is obtained by summing the contribution from the smooth DM componentand the contributions from each subhalo 68
  • 69. DM annihilation distributionΔ2Ms gives the average enhancement in the source due to a subhalo of mass Ms,Δ2 is the sum over all contributions weighted over the subhalo MF times Ms 69
  • 70. Viable DM candidates: signals Neutralinos Sterile ν’s Annihilation Radiative decay: line νs → να + γ DM annihilation flux DM decay flux 1 ρ DM ( r ) 2 1 ρ DM ( r )F ∝ 2 2 〈σ V 〉 Astro physics F ∝ 2 〈 Γ rad 〉 DL Mχ DL Mv  dE × [ f ann ( E ; χ )]  Particle physics [ ]  dE  × Eγ ( M v )    dν   dν  70
  • 71. Outline Multi-epoch The Dark Matter Timeline The present Multi-Scale + M3 Galactic center Galactic structures Galaxy Clusters The Future The DM search challenge 71
  • 72. THANKSfor your attention ! 72