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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 and Luminous Matter . 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 and LuminousMatter. 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 is empirically described at all times by the universal (NFW) profile (Navarro+96,97). More massive halos and those formed earlier have larger overdensitiesd. Object today virialized: mean halo density inside Rvir= 100 ϱc Concentration c=Rvir/ rs

  5. The concentration scales with mass and redshift (Zhao+03,08; Gao+08, Klypin+10): At z=0, c decreases with mass. -> Movie 1

  6. Aquarius simulations, highest mass resolution to date. Density distribution: still a cuspy profile but similar to the Einasto Law Navarro+10 No difference, for mass modelling, with the NFW one. density and circular velocity for an halo of 1012 MSUN V=const

  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 Dwarfs Spirals : stellar disk +bulge+HI disk Ellipticals & dSph: stellar spheroid The distribution of luminous matter :

  8. SPIRALS

  9. Stellar Disks M33verysmoothstructure 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 GAS DISTRIBUTION HI Flattishradialdistribution Deficiency in the 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 EXEMPLE OF HIGH QUALITY RC V(R/RD) R/RD

  13. Earlydiscoveryfromoptical and HI RCs observed disk no RC followsthe disk velocityprofile disk 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 in Galaxies The distributionofgravitatingmatter, unlike the luminousone, isluminositydependent. Tully-Fisher relation existsat locallevel (radiiRi) no DM Yegorovaet al 2007

  16. mag Salucci+07 6 RD Rotation Curves Coaddedfrom 3200 individualRCs TYPICAL INDIVIDUAL RCs OF INCREASING LUMINOSITY Low lum high lum

  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 Extrapolationof URC out tovirialradiusbyusing -> Movie 2

  18. Extrapolating the Universal Curve to the VirialRadius Mh Shankaret al 2006 Mandelbaumet al 2006 Virial halo masses Mh and VVIR are obtained - directly by weak-lensing analysis - indirectly by correlating dN/dL with theoretical DM halo dN/dM

  19. An Universal Mass Distribution ΛCDM URC Observed URC 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 (Burkert) Dark haloswithcusps(NFW, Einasto) The mass modelhas 3 free parameters: disk mass, halocentral density and core radi radius (halolength-scale). NFW Burkert

  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 ofhalocoreradiusrc • Kormendy & Freeman (2004) 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 NFW Burkert gas gas B disk B disk Generalresultsfromseveralsamplesincluding THINGS, HI surveyofuniform and high quality data • - Non-circularmotions are small. • - No DM haloelongation • - ISO/Burkerthalospreferredover NFW • Tri-axiality and non-circularmotionscannotexplain the CDM/NFW cusp/corediscrepancy gas disk

  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 Surfacebrightnessofellipticalsfollows 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 Dispersionvelocitiesofstars or PlanetaryNebulae 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 SDSS early-typegalaxies Bernardi et al. 2003 Fromvirialtheorem Hyde & Bernardi 2009 Fitting gives: a=1.8 , b~0.8) then: FP “tilt” due tovariationswithσ0of: Dark matterfraction? Stellar population?

  31. Dark-Luminous mass decomposition of dispersion velocities • Not an unique model: example a giant elliptical with reasonable parameters RESULTSThe spheroid determines the aperture dispersion velocity Stars dominate inside ReMore complications when:presence of anisotropiesdifferent halo profile (e.g. Burkert) 1011 Two components: NFW halo, Sersic spheroid Assumed isotropy Mamon& Łokas05 Dark matterprofileunresolved

  32. Weakand strong lensing SLACS: Gavazzi et al. 2007) Gavazzi et al 2007 Inside Re, the total (spheroid + dark halo) mass increasesproportionallyto the radius UNCERTAIN DM DENSITY PROFILEI

  33. Mass ProfilesfromX-ray Nigishitaet al 2009 Temperature Density M/L profile NO DM HydrostaticEquilibrium • CORED HALOS?

  34. The mass in stars in galaxies The luminousmatterin the formofstarsM*is a fundamentalquantity. Itoftenplays a role in inferring the propertiesofDark Matter M*/L ofa galaxyobtainedvia Stellar PopulationSynthesismodels Fitted SED Dynamical and photometricestimatesagree Shankar & Bernardi 2009

  35. 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

  36. dSphs

  37. 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

  38. 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 STELLAR SPHEROID

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

  40. Mass profiles of dSphs Jeans’ models provide the most objective sample comparison • Jeans equation relates kinematics, light and underlying mass distribution • Make assumptions on the velocity anisotropy and then fit the dispersion profile n(R) PLUMMER PROFILE DENSITY PROFILE Results point to cored distributions Gilmoreet al 2007

  41. Degeneracy between DM mass profile and velocity anisotropy Cusped and cored mass models fit dispersion profiles equally well Walkeret al 2009 However: dSphscoredmodelstructuralparametersagreewiththoseofSpirals and Ellipticals σ(R) km/s Halocentral density vs coreradius NFW+anisotropy = CORED Donato et al 2009

  42. Global trend of dSph haloes UNIQUE MASS PROFILE ? Mateoet al 1998 Gilmoreet al 2007 • Sculptor AndII M ~ the SAME in alldwarfspheroidals Strigariet al 2008

  43. 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

  44. WEAK LENSING

  45. Weak Lensing around galaxies • Criticalsurface density Lensingequationfor the observedtangentialshear NFW B SAME VALUES FOUND FROM THE URC Donato et al 2009

  46. MODELLING WEAK LENSING SIGNALS Lenses: 170 000 isolatedgalaxies, Sources : 30 M SDSS galaxies NFW 0.1 0.1 tar tar Mandelbaumet al 2009 • HALO MASS FUNCTION OF LUMINOSITY EXTENDED HALOS EXIST DENSITY PROFILE: NFW/BURKERT HALO MASSES: exceed the stellar masses more than the cosmologicalvalue correlate with the mass of the stellar components tHALOS EXTEND OUT TO VIRIAL RADII ar

  47. GALAXY HALOS: WHAT WE KNOW Mass correlates with luminosity URC mass profile Mh(r) = F(r/Rvir, Mvir) valid for S, dSph, LSB, to check 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, KF, 2004

  48. DETECTING DARK MATTER

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