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Dec. 1-8, 2010

DARK MATTER IN GALAXIES. NAME. INSTITUTE. Dec. 1-8, 2010. Overview The concept of Dark Matter Dark Matter in Spirals , Ellipticals , dSphs Dark Matter at outer radii . Global properties Direct and Indirect Searches of Dark Matter. What is Dark Matter?.

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Dec. 1-8, 2010

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  1. DARK MATTER IN GALAXIES NAME INSTITUTE Dec. 1-8, 2010

  2. Overview The conceptof Dark Matter Dark Matter in Spirals, Ellipticals, dSphs Dark Matter at outerradii. Global properties Directand IndirectSearchesof Dark Matter

  3. What is Dark Matter? In a galaxy, the radialprofileof the gravitatingmatter M(r) and thatof the sum ofallluminouscomponentsML(r) do not match. A MASSIVE DARK COMPONENT isintroducedto account for the disagreement: Itsprofile MH(r) mustobey: The DM phenomenon can beinvestigatedonlyifweaccuratelymeausure the distributionof: Luminousmatter. Gravitatingmatter.

  4. Dark Matter Profiles from N-body simulations In ΛCDM scenario the density profile for virialized DM halos of all masses of all masses is empirically described at all times by the universal NFW formula (Navarro+96,97). More massive and halos formed earlier have larger overdensitiesd. Concentration c=R200/ rsis an alternative density measure.

  5. The concentration scales with mass and redshift (Zhao+03,08; Gao+08, Klypin+10): At low z, c decreases with mass. -> Movie 1

  6. Aquarius simulations, highest resolutions to date. Results: CuspyEinasto profiles (Navarro+10). No difference for mass modelling with NFW ones with a dependent slightly on mass.

  7. The Realm of Galaxies The range of galaxies in magnitude, types and central surface density : 15 mag, 4 types, 16 mag arsec2 Centralsurfacebrightness vs galaxymagnitude Spirals : stellar disk +bulge+HI disk Ellipticals & dSph: stellar spheroid The distribution of luminous matter :

  8. SPIRALS

  9. Stellar Disks M33 - outer disk truncated, verysmoothstructure NGC 300 - exponential disk goes for at least 10 scale- lengths scale radius Bland-Hawthornet al 2005 Ferguson et al 2003

  10. Wong & Blitz (2002) Gas surfacedensities HI Flattishradialdistribution Deficiencyin centre CO and H2 Roughlyexponential Negligible mass

  11. Circularvelocitiesfromspectroscopy - Opticalemissionlines (H, Na) - Neutralhydrogen (HI)-carbonmonoxide (CO) Tracerangularspectralresolutionresolution HI 7" … 30" 2 … 10 km s-1 CO 1.5" … 8" 2 … 10 km s-1 H, … 0.5" … 1.5" 10 … 30 km s-1

  12. ROTATION CURVES (RC) Symmetriccircular rotation of a disk characterizedby • Sky coordinatesof the galaxycentre • SystemicvelocityVsys • CircularvelocityV(R) • Inclination angle •  = azimuthal angle Exampleof a recent high quality RC: Radial coordinate in unitsof RD V(R/RD) V(2) R/RD

  13. Earlydiscoveryfromoptical and HI RCs observed disk no RC followsthe disk velocityprofile Rubinet al 1980 Mass discrepancy AT OUTER RADII

  14. Extended HI kinematicstraces dark matter - - Light (SDSS) HI velocityfield • NGC 5055 SDSS Bosma, 1981 GALEX Bosma, 1981 Radius (kpc) Bosma 1979 The mass discrepancyemergesas a disagreementbetween light and mass distributions

  15. Evidencefor a Mass Discrepancy The distributionofgravitatingmatterisluminositydependent. Tully-Fisher relation existsat locallevel (radiiRi) no DM slope Yegorovaet al 2007

  16. mag. PSS 6 RD Rotation Curves Coaddedfrom 3200 individualRCs TYPICAL INDIVIDUAL RC low high

  17. The Conceptof the Universal Rotation Curve (URC) The CosmicVarianceof the valueof V(x,L) in galaxiesofsameluminosityL at the sameradiusx=R/RDisnegligiblecomparedto the variationsthat V(x,L) showsasx and L varies. The URC out to 6 RD isderiveddirectlyfromobservations Howto extrapolate the URC out tovirialradius? Needed -> Movie 2

  18. Extrapolating the URC to the Virialradius Shankaret al 2006 Virial halo masses and VVIR are obtained - directly by weak-lensing - indirectly by correlating dN/dL with theoretical DM halo dN/dM

  19. An Universal Mass Distribution ΛCDM theoretical URC from NFW Observed URC profileand MMW theory NFW theory low obs high obs Salaucci+,2007

  20. Rotation curve analysis From data to mass models Vtot2 = VDM2 + Vdisk2 + Vgas2 • fromI-bandphotometry • from HI observations Dark haloswithconstant density cores Dark haloswithcusps(NFW, Einasto) Modelhasthree free parameters: disk mass, halocentral density and coreradius (halolength-scale).

  21. halocentral density coreradius luminosity MASS MODELLING RESULTS highestluminosities lowestluminosities halo disk disk halo halo disk Allstructural DM and LM parameters are related withluminosity.g Smallergalaxies are denser and have a higherproportionof dark matter. fractionof DM

  22. Dark HaloScalingLaws Thereexistrelationshipsbetweenhalostructuralquantiies and luminosity. Investigated via mass modellingofindividualgalaxies - Assumption:MaximunDisk, 30 objects -the slopeof the halo rotation curve near the center givesthe halocore density - extendedRCsprovidean estimate ofhalocoreradiusrcrc • Kormendy & Freeman (2003) o o ~ LB- 0.35 rc ~ LB0.37  ~LB0.20 rc The centralsurfacedensity  ~ orc=constant 3.0 2.5 2.0 1.5 1.0 

  23. The distributionof DM aroundspirals UsingindividualgalaxiesGentile+ 2004, de Blok+ 2008  Kuzio de Naray+ 2008, Oh+  2008, Spano+ 2008, Trachternach+ 2008, Donato+,2009 A detailedinvestigation: high quality data and modelindependentanalysis

  24. DDO 47 NGC3621 Generalresultsfromseveralsamplesincluding THINGS, HI surveyofuniform and high quality data - Non-circularmotions are small. - No DM haloelongation - ISO halosoftenpreferredover NFW Tri-axiality and non-circularmotionscannotexplain the CDM/NFW cusp/corediscrepancy

  25. SPIRALS: WHAT WE KNOW AN UNIVERSAL CURVE REPRESENTS THE ALL INDIVIDUAL RCs MORE PROPORTION OF DARK MATTER IN SMALLER SYSTEMS RADIUS IN WHICH THE DM SETS IN FUNCTION OF LUMINOSITY MASS PROFILE AT LARGER RADII COMPATIBLE WITH NFW DARK HALO DENSITY SHOWS A CENTRAL CORE OF SIZE 2 RD

  26. ELLIPTICALS

  27. The Stellar Spheroid Surfacebrightnessfollows a Sersic (de Vaucouleurs) law Re : the effectiveradius • Bydeprojecting I(R) weobtain the luminosity density j(r): ESO 540 -032 Sersicprofile

  28. ModellingEllipticals Measure the light profile Derive the total mass profilefrom DispersionvelocitiesofstarsPlanetaryNebulae X-raypropertiesof the emitting hot gas Combiningweak and strong lensing data Disentangle the dark and the stellar components

  29. Line-of-sight, projected Velocity Dispersions, 2-D kinematics SAURON data of N 2974

  30. The Fundamental Plane: central dispersion velocity, half light radius and central surface brightness are related Bernardi et al. 2003 SDSS early-typegalaxies Fromvirialtheorem • Fitting r ~ aIbgives: (a<2, b~0.8) → M/L notconstant ~ L0.14 Hyde & Bernardi 2009 Shankar & Bernardi 2009 The FP “tilt” is due tovariations in: Dark matterfraction? Stellar population? Likely.

  31. Dark-Luminous mass decomposition of dispersion velocities Stars dominate inside ReDark matterprofileunresolved Assumed IsotropyThree components: DM, stars, Black Holes Mamon& Łokas05

  32. Weakand strong lensing SLACS: Gavazzi et al. 2007) Gavazzi et al 2007 Inside R_e, the total (spheroid + dark halo) mass increases in proportionto the radius

  33. Mass ProfilesfromX-ray Nigishitaet al 2009 Temperature Density M/L profile NO DM Hydrostatic Equilibrium

  34. ELLIPTICALS: WHAT WE KNOW A LINK AMONG THE STRUCTURAL PROPERTIES OF STELLAR SPHEROID SMALL AMOUNT OF DM INSIDE RE MASS PROFILE COMPATIBLE WITH NFW AND BURKERT DARK MATTER DIRECTLY TRACED OUT TO RVIR

  35. dSphs

  36. Dwarf spheroidals: basic properties • Low luminosity, gas-free satellites of Milky Way and M31 • Large mass-to-light ratios (10 to 100 ), smallest stellar systems containing dark matter Luminosities and sizes of Globular Clusters and dSph Gilmoreet al 2009

  37. Kinematics of dSph • 1983: Aaronson measured velocity dispersion of Draco based on observations of 3 carbon stars - M/L ~ 30 1997: First dispersion velocity profile of Fornax (Mateo)2000+: Dispersion profiles of all dSphs measured using multi-object spectrographs Instruments: AF2/WYFFOS (WHT, La Palma); FLAMES (VLT); GMOS (Gemini); DEIMOS (Keck); MIKE (Magellan) 2010: full radial coverage in each dSph, with 1000 stars per galaxy

  38. Dispersion velocity profiles Wilkinson et al 2009 dSph dispersion profiles generally remain flat to large radii

  39. Mass profiles of dSphs • Jeans equation relates kinematics, light and underlying mass distribution • Make assumptions on the velocity anisotropy and then fit the dispersion profile Results point to cored distributions Jeans’ models provide the most objective sample comparison

  40. Degeneracy between DM mass profile and velocity anisotropy Cusped and cored mass models fit dispersion profiles equally well However: dSphscoreddistributionstructuralparametersagreewiththoseofSpirals and Ellipticals Halocentral density vs coreradius Walkeret al 2009 Donato et al 2009

  41. Global trend of dSph haloes • Sculptor AndII Mateoet al 1998 Gilmoreet al 2007

  42. DSPH: WHAT WE KNOW PROVE THE EXISTENCE OF DM HALOS OF 1010 MSUN AND ρ0 =10-21 g/cm3 DOMINATED BY DARK MATTER AT ANY RADIUS MASS PROFILE CONSISTENT WITH THE EXTRAPOLATION OF THE URC HINTS FOR THE PRESENCE OF A DENSITY CORE

  43. The stellar mass ofgalaxies The luminousmatterin the formofstarsM*is a crucialquantity. Indispensabletoinfer the amountof Dark Matter M*/L ofa galaxyobtainedvia Stellar PopulationSynthesismodels Fitted SED Dynamical and photometricestimatesagree

  44. WEAK LENSING

  45. Weak Lensing around galaxies • Criticalsurface density Lensingequationfor the observedtangentialshear Donato et al 2009

  46. Mandelbaumet al 2009 HALO MASSES ARE A FUNCTION OF LUMINOSITY

  47. GALAXY HALOS: WHAT WE KNOW Mass correlates with luminosity URC mass profile Mh(r) = F(r/Rvir, Mvir) valid for S, dSph, LSB, checking for E Unique mass profile Mh(r) = G(r) Unique value of halo central surface density Mandelbaum,+ 06 Walker+ 2010 Salucci+ 2007 Walker+ 2010 Donato et al. 2009

  48. DETECTING DARK MATTER

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