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Insights into Dark Matter         Hints and Signals from Astrophysics         Katherine J. Mack         University of Melb...
a slice of the universe pieTuesday, 5 March 13                    2
what we know               Dark matter is:                      Massive (gravitationally attractive & clustering)         ...
what we don’t know               Fundamental nature of dark matter               How dark matter formed in the universe   ...
the evidence amasses               Rotation curves & galactic dynamics (missing mass)               Cluster dynamics (miss...
the evidence amasses               Rotation curves & galactic dynamics (missing mass)               Cluster dynamics (miss...
the evidence amasses               Rotation curves & galactic dynamics (missing mass)               Cluster dynamics (miss...
the evidence amasses               Rotation curves & galactic dynamics (missing mass)               Cluster dynamics (miss...
the evidence amasses               Rotation curves & galactic dynamics (missing mass)               Cluster dynamics (miss...
cosmological microlensing                                     ESOTuesday, 5 March 13                        10
cosmological microlensing                                      1454                                                       ...
the evidence amasses               Rotation curves & galactic dynamics (missing mass)               Cluster dynamics (miss...
WMAP 9                         SPT                         ACT                      Hinshaw et al. 2013Tuesday, 5 March 13...
the evidence amasses               Rotation curves & galactic dynamics (missing mass)               Cluster dynamics (miss...
Tuesday, 5 March 13   15
the evidence amasses               Rotation curves & galactic dynamics (missing mass)               Cluster dynamics (miss...
dark matter’s smoking gun:         the Bullet ClusterTuesday, 5 March 13                   17
dark matter’s smoking gun:         the Bullet ClusterTuesday, 5 March 13                   18
dark matter’s smoking gun:         the Bullet ClusterTuesday, 5 March 13                   19
dark matter’s smoking gun:         the Bullet ClusterTuesday, 5 March 13                   20
classes of dark matter               Annihilating DM (e.g., SUSY neutralino WIMP)               Decaying DM (e.g., axino) ...
small-scale power               Dark matter particle interactions alter structure on small               scales (smaller t...
missing satellites problem                                          Milky Way seems to have                               ...
Navarro, Frenk & White 1997         cusp/core problem                                    r -1                             ...
warm dark matter               WDM has a free-streaming scale               within which structures are smooth            ...
self-interacting DM               Has been proposed to explain cores in               galaxies and low numbers of substruc...
cosmic ray excesses               Positron excess seen at PAMELA experiment, confirmed with Fermi               Hints of e+...
cosmic ray excesses               Positron excess seen at PAMELA experiment, confirmed with Fermi               Hints of e+...
cosmic ray excesses               BUT it could be               pulsars               No directional               informa...
130 GeV line(s) in Galactic Center               Hints have been seen by the Fermi               satellite of emission aro...
future: signatures at early times               Dark matter annihilation or               decay can alter the         M.E....
outlook               Future data (Fermi, AMS, PAMELA, etc) will help pin               down anomalies               Simul...
dark matter annihilates                      altered radiation field                                                       ...
up for discussion               What does the particle physics community want from               the astronomers?         ...
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Insights into Dark Matter

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Slides from my presentation at the Joint CoEPP-CAASTRO Workshop (http://www.caastro.org/event/2013/coepp), 28 February 2013. Brief overview of the evidence for dark matter in the Universe, plus discussion of challenges, hints of possible signals, and some references for further reading.

The presentation time-slot was 30 minutes + 20 minutes discussion.

Published in: Education
  • This is awesome. First you used the exact same slide template which I used for my university project: instant connection. Then the informative content of your slides served as the glue to fuse my connected mind into a oneness with the concept. Thank you for throwing some light on the Dark Matter(s).
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Insights into Dark Matter

  1. 1. Insights into Dark Matter Hints and Signals from Astrophysics Katherine J. Mack University of Melbourne www.ph.unimelb.edu.au/~kmack : @AstroKatieTuesday, 5 March 13 1
  2. 2. a slice of the universe pieTuesday, 5 March 13 2
  3. 3. what we know Dark matter is: Massive (gravitationally attractive & clustering) Cold (slow-moving) Collisionless (passes through itself and other matter) Dark (does not emit or absorb light) Non- (or weakly-) interacting (no detected non- gravitational interactions with other particles)Tuesday, 5 March 13 3
  4. 4. what we don’t know Fundamental nature of dark matter How dark matter formed in the universe Whether dark matter has any non-gravitational interaction with standard model particles Whether dark matter has any non-gravitational interaction with itselfTuesday, 5 March 13 4
  5. 5. the evidence amasses Rotation curves & galactic dynamics (missing mass) Cluster dynamics (missing mass) Strong & weak gravitational lensing (missing mass / halo shapes / substructure) Gravitational microlensing (smooth distribution of mass) CMB acoustic peaks (DM/baryon ratio) Matter power spectrum & structure formation (DM/baryon ratio) Cluster collisions (missing mass / collisionless matter)Tuesday, 5 March 13 5
  6. 6. the evidence amasses Rotation curves & galactic dynamics (missing mass) Cluster dynamics (missing mass) Strong & weak gravitational lensing (missing mass / halo shapes / substructure) Gravitational microlensing (smooth distribution of mass) CMB acoustic peaks (DM/baryon ratio) Matter power spectrum & structure formation (DM/baryon ratio) Cluster collisions (missing mass / collisionless matter)Tuesday, 5 March 13 6
  7. 7. the evidence amasses Rotation curves & galactic dynamics (missing mass) Cluster dynamics (missing mass) Strong & weak gravitational lensing (missing mass / halo shapes / substructure) Gravitational microlensing (smooth distribution of mass) CMB acoustic peaks (DM/baryon ratio) Matter power spectrum & structure formation (DM/baryon ratio) Cluster collisions (missing mass / collisionless matter)Tuesday, 5 March 13 7
  8. 8. the evidence amasses Rotation curves & galactic dynamics (missing mass) Cluster dynamics (missing mass) Strong & weak gravitational lensing (missing mass / halo shapes / substructure) Gravitational microlensing (smooth distribution of mass) CMB acoustic peaks (DM/baryon ratio) Matter power spectrum & structure formation (DM/baryon ratio) Cluster collisions (missing mass / collisionless matter)Tuesday, 5 March 13 8
  9. 9. the evidence amasses Rotation curves & galactic dynamics (missing mass) Cluster dynamics (missing mass) Strong & weak gravitational lensing (missing mass / halo shapes / substructure) Gravitational microlensing (smooth distribution of mass) CMB acoustic peaks (DM/baryon ratio) Matter power spectrum & structure formation (DM/baryon ratio) Cluster collisions (missing mass / collisionless matter)Tuesday, 5 March 13 9
  10. 10. cosmological microlensing ESOTuesday, 5 March 13 10
  11. 11. cosmological microlensing 1454 MEDIAVILLA ET AL. Vol. 706 α=0.01 α=0.05 α=0.1 Lensing of background quasars by galaxies can give insight into galaxy mass distributions α=0.15 α=0.2 α=0.25 Constraints can be placed on fraction of mass in compact α=0.3 α=0.5 α=1 sources (stars) Constraint: α < 10% Figure 2. Example of magnification maps for the case κ = γ = 0.45. From top to bottom and from left to right, maps correspond to α = 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.50, 1.00. Mediavilla et al. 2009 2. OBSERVED MICROLENSING MAGNIFICATIONS AND For some of the image pairs (∼30% of the sample) there MACRO-LENS MODELS are mid-IR flux ratios available. Except for one system, SDSS J1004+4112 (where image C is probably affected by extinction, We collected the data, ∆m (see Equation (4)), examining all ´ G´ mez-Alvarez et al. 2006), they are in very good agreement o the optical spectroscopy5 found in the literature (see Table 1). In with the emission-line flux ratios (see Table 2). The average most cases, the microlensing magnification or the scaling of the difference between mid-IR and emission line flux ratios is onlyTuesday, 5 March 13 emission line ratio with respect to the continuum ratio are di- 11
  12. 12. the evidence amasses Rotation curves & galactic dynamics (missing mass) Cluster dynamics (missing mass) Strong & weak gravitational lensing (missing mass / halo shapes / substructure) Gravitational microlensing (smooth distribution of mass) CMB acoustic peaks (DM/baryon ratio) Matter power spectrum & structure formation (DM/baryon ratio) Cluster collisions (missing mass / collisionless matter)Tuesday, 5 March 13 12
  13. 13. WMAP 9 SPT ACT Hinshaw et al. 2013Tuesday, 5 March 13 13
  14. 14. the evidence amasses Rotation curves & galactic dynamics (missing mass) Cluster dynamics (missing mass) Strong & weak gravitational lensing (missing mass / halo shapes / substructure) Gravitational microlensing (smooth distribution of mass) CMB acoustic peaks (DM/baryon ratio) Matter power spectrum & structure formation (DM/baryon ratio) Cluster collisions (missing mass / collisionless matter)Tuesday, 5 March 13 14
  15. 15. Tuesday, 5 March 13 15
  16. 16. the evidence amasses Rotation curves & galactic dynamics (missing mass) Cluster dynamics (missing mass) Strong & weak gravitational lensing (missing mass / halo shapes / substructure) Gravitational microlensing (smooth distribution of mass) CMB acoustic peaks (DM/baryon ratio) Matter power spectrum & structure formation (DM/baryon ratio) Cluster collisions (missing mass / collisionless matter)Tuesday, 5 March 13 16
  17. 17. dark matter’s smoking gun: the Bullet ClusterTuesday, 5 March 13 17
  18. 18. dark matter’s smoking gun: the Bullet ClusterTuesday, 5 March 13 18
  19. 19. dark matter’s smoking gun: the Bullet ClusterTuesday, 5 March 13 19
  20. 20. dark matter’s smoking gun: the Bullet ClusterTuesday, 5 March 13 20
  21. 21. classes of dark matter Annihilating DM (e.g., SUSY neutralino WIMP) Decaying DM (e.g., axino) Warm DM (WDM) (e.g., sterile neutrino) Self-interacting DM (SIDM) (particle + dark sector force) Axion DM (e.g., QCD axion / string axion) MACHO DM (e.g., primordial black holes)Tuesday, 5 March 13 21
  22. 22. small-scale power Dark matter particle interactions alter structure on small scales (smaller than galaxies, clusters) Look at: Lyman-alpha forest, substructures, satellites...Tuesday, 5 March 13 22
  23. 23. missing satellites problem Milky Way seems to have fewer satellite galaxies than expected in CDM simulations Caveats: MW may not be typical Baryonic effects might account for dearth (see Madau et al. 2008 e.g. Brooks et al. 2013)Tuesday, 5 March 13 23
  24. 24. Navarro, Frenk & White 1997 cusp/core problem r -1 r -3 Inner profiles of galaxies observed to flatten out (to a constant-density “core”) Self-interacting & warm dark matter models sometimes invoked BUT could be solved with baryon physics Supernova feedback can expel gas from galaxy non- adiabatically This can flatten the DM cusp into a core Pontzen & Governato 2012Tuesday, 5 March 13 24
  25. 25. warm dark matter WDM has a free-streaming scale within which structures are smooth “Erases” small-scale structure in the matter power spectrum Invoked for substructures, satellites Constrained by Lyman-alpha forest measurements BUT: core size - mass relation Bode, Ostriker & Turok 2001 doesn’t hold upTuesday, 5 March 13 25
  26. 26. self-interacting DM Has been proposed to explain cores in galaxies and low numbers of substructures Yoshida et al. 2000 in dark matter halos Effects: fewer substructures smoother structure cored inner density profiles Currently being tested with cluster collision modellingTuesday, 5 March 13 26
  27. 27. cosmic ray excesses Positron excess seen at PAMELA experiment, confirmed with Fermi Hints of e+ + e- spectrum feature; no antiproton excess 3 TeV DM with high cross-section proposed as explanation Cirelli 2012Tuesday, 5 March 13 27
  28. 28. cosmic ray excesses Positron excess seen at PAMELA experiment, confirmed with Fermi Hints of e+ + e- spectrum feature; no antiproton excess 3 TeV DM with high cross-section proposed as explanation 3 TeV DM particle annihilating into τ+τ− with cross section 2 · 10−22 cm3/ sec Cirelli 2012Tuesday, 5 March 13 28
  29. 29. cosmic ray excesses BUT it could be pulsars No directional information available Pulsars are known to produce electron/positron pairs Grasso et al. 2009Tuesday, 5 March 13 29
  30. 30. 130 GeV line(s) in Galactic Center Hints have been seen by the Fermi satellite of emission around 130 GeV from the Galactic Center Best fit actually two lines Su & Finkbeiner 2012 Line emission could be a “smoking gun” of DM annihilation -- hard to make with astrophysics BUT signal significance currently low & some observational uncertainties remainTuesday, 5 March 13 30
  31. 31. future: signatures at early times Dark matter annihilation or decay can alter the M.E.DE.A. code M.Valdés, CE, A.Ferrara, MNRAS, 2011 evolution of the intergalactic medium heating Energy injection heats & injected particle ionizes gas Lyman photons ionization Signals may be seen in Image from talk by Carmello Evoli • MEDEA follows every particle from TeV down to eV energies in a continuous way. redshifted 21cm line of • Previous works have considered electrons up to keV only (e.g. J.M.Shull & M.E. van Steenberg, APJ, 1985; S.Furlanetto & S.J.Stoever,!MNRAS, 2010). neutral hydrogen giovedì 26 aprile 12Tuesday, 5 March 13 31
  32. 32. outlook Future data (Fermi, AMS, PAMELA, etc) will help pin down anomalies Simulations and modelling needed to check on possible inconsistencies / hints More accurate modelling of DM+baryon physics (to make DM identification possible) (→Alan Duffy) Cosmological models that include dark matter physics (to see effects at early times) (→me+group)Tuesday, 5 March 13 32
  33. 33. dark matter annihilates altered radiation field dark matter halos heat at early times themselves altered small-scale power altered Pop III / change in IGM dark stars evolution (heating/ ionization) change in SMBH production from direct collapse / altered H2 abundance quasistars DRAGONS (Dark-ages Reionization And Galaxy Formation Simulation) 21cm global 21cm power signal spectrumTuesday, 5 March 13 33
  34. 34. up for discussion What does the particle physics community want from the astronomers? What kind of signal would convince us we’ve seen dark matter particle physics? Should we still be considering dark matter alternatives / modified gravity?Tuesday, 5 March 13 34

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