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

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? In a galaxy, the radial profile of the gravitating matter M(r) and that of the sum of all luminous components M L (r) do not match. A MASSIVE DARK COMPONENT is introduced to account for the disagreement: Its profile M H (r) must obey: The DM phenomenon can be investigated only if we accurately meausure the distribution of: Luminous matter. Gravitating matter.

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 overdensities . Concentration c=R 200 / r s is an alternative density measure.

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

Aquarius simulations, highest resolutions to date. Results: Cuspy Einasto profiles (Navarro+10). No difference for mass modelling with NFW ones with  dependent slightly on mass.

Central surface brightness vs galaxy magnitude The Realm of Galaxies The range of galaxies in magnitude, types and central surface density : 15 mag, 4 types, 16 mag arsec 2 Spirals : stellar disk +bulge +HI disk Ellipticals & dSph: stellar spheroid The distribution of luminous matter :

SPIRALS

Stellar Disks M33 - outer disk truncated, very smooth structure NGC exponential disk goes for at least 10 scale- lengths Bland-Hawthorn et al 2005 Ferguson et al 2003 scale radius

HI Flattish radial distribution Deficiency in centre CO and H 2 Roughly exponential Negligible mass Wong & Blitz (2002) Gas surface densities

Circular velocities from spectroscopy - Optical emission lines (H  a) - Neutral hydrogen (HI)-carbon monoxide (CO) Tracer angular spectral resolution resolution HI 7" … 30" 2 … 10 km s -1 CO1.5" … 8" 2 … 10 km s -1 H , …0.5" … 1.5" 10 …30 km s -1

ROTATION CURVES (RC) Symmetric circular rotation of a disk characterized by Sky coordinates of the galaxy centre Systemic velocity V sys Circular velocity V(R) Inclination angle  = azimuthal angle Example of a recent high quality RC: Radial coordinate in units of R D V(2) V(R/R D ) R/R D

Early discovery from optical and HI RCs Rubin et al 1980

The mass discrepancy emerges as a disagreement between light and mass distributions GALEX SDSS Extended HI kinematics traces dark matter - - NGC 5055 Light (SDSS) HI velocity field Bosma, 1981 Bosma 1979 Radius (kpc)

Evidence for a Mass Discrepancy The distribution of gravitating matter is luminosity dependent. Tully-Fisher relation exists at local level (radii R i ) Yegorova et al 2007

Rotation Curves Coadded from 3200 individual RCs PSS 6 R D mag. TYPICAL INDIVIDUAL RC low high

The Concept of the Universal Rotation Curve (URC) The Cosmic Variance of the value of V(x,L) in galaxies of same luminosity L at the same radius x=R/R D is negligible compared to the variations that V(x,L) shows as x and L varies. The URC out to 6 R D is derived directly from observations How to extrapolate the URC out to virial radius? Needed -> Movie 2

Extrapolating the URC to the Virial radius Virial halo masses and V VIR are obtained - directly by weak-lensing - indirectly by correlating dN/dL with theoretical DM halo dN/dM Shankar et al 2006

An Universal Mass Distribution ΛCDM theoretical URC from NFW Observed URC profile and MMW theory NFW high low Salaucci+,2007 theory obs

Rotation curve analysis From data to mass models ➲ from I-band photometry ➲ from HI observations ➲ Dark halos with constant density cores Dark halos with cusps (NFW, Einasto) Model has three free parameters: disk mass, halo central density and core radius (halo length-scale). V tot 2 = V DM 2 + V disk 2 + V gas 2

core radius halo central density luminosity disk halo disk MASS MODELLING RESULTS fraction of DM lowest luminosities highest luminosities All structural DM and LM parameters are related with luminosity.g Smaller galaxies are denser and have a higher proportion of dark matter.

Dark Halo Scaling Laws There exist relationships between halo structural quantiies and luminosity. Investigated via mass modelling of individual galaxies - Assumption: Maximun Disk, 30 objects -the slope of the halo rotation curve near the center gives the halo core density - extended RCs provide an estimate of halo core radiusr c r c Kormendy & Freeman (2003)  o ~ L B r c ~ L B 0.37  ~ L B 0.20 oo rcrc  The central surface density  ~  o r c =constant

The distribution of DM around spirals Using individual galaxies Gentile+ 2004, de Blok Kuzio de Naray+ 2008, Oh+ 2008, Spano+ 2008, Trachternach+ 2008, Donato+,2009 A detailed investigation: high quality data and model independent analysis

NGC Non-circular motions are small. - No DM halo elongation - ISO halos often preferred over NFW Tri-axiality and non-circular motions cannot explain the CDM/NFW cusp/core discrepancy General results from several samples including THINGS, HI survey of uniform and high quality data DDO 47

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 R D

ELLIPTICALS

Surface brightness follows a Sersic (de Vaucouleurs) law R e : the effective radius By deprojecting I(R) we obtain the luminosity density j(r): The Stellar Spheroid ESO Sersic profile

Modelling Ellipticals Measure the light profile Derive the total mass profile from Dispersion velocities of stars Planetary Nebulae X-ray properties of the emitting hot gas Combining weak and strong lensing data Disentangle the dark and the stellar components

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

The Fundamental Plane: central dispersion velocity, half light radius and central surface brightness are related SDSS early-type galaxies Fitting r ~  a I b gives: (a<2, b~0.8) → M/L not constant ~ L 0.14 From virial theorem The FP “tilt” is due to variations in: Dark matter fraction? Stellar population? Likely. Bernardi et al Shankar & Bernardi 2009 Hyde & Bernardi 2009

Stars dominate inside R e Dark matter profile unresolved Mamon & Łokas 05 Assumed Isotropy Three components: DM, stars, Black Holes Dark-Luminous mass decomposition of dispersion velocities

Weak and strong lensing SLACS: Gavazzi et al. 2007) Inside R_e, the total (spheroid + dark halo) mass increases in proportion to the radius Gavazzi et al 2007

Mass Profiles from X-ray Temperature Density Hydrostatic Equilibrium M/L profile NO DM Nigishita et al 2009

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

dSphs

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

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

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

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

Degeneracy between DM mass profile and velocity anisotropy Cusped and cored mass models fit dispersion profiles equally well However: dSphs cored distribution structural parameters agree with those of Spirals and Ellipticals Halo central density vs core radius  Walker et al 2009 Donato et al 2009

Global trend of dSph haloes Sculptor AndII Mateo et al 1998 Gilmore et al 2007

DSPH: WHAT WE KNOW PROVE THE EXISTENCE OF DM HALOS OF M SUN AND ρ 0 = g/cm 3 DOMINATED BY DARK MATTER AT ANY RADIUS MASS PROFILE CONSISTENT WITH THE EXTRAPOLATION OF THE URC HINTS FOR THE PRESENCE OF A DENSITY CORE

The stellar mass of galaxies The luminous matter in the form of stars M * is a crucial quantity. Indispensable to infer the amount of Dark Matter M*/L of a galaxy obtained via Stellar Population Synthesis models Fitted SED Dynamical and photometric estimates agree

WEAK LENSING

Weak Lensing around galaxies Critical surface density Lensing equation for the observed tangential shear Donato et al 2009

HALO MASSES ARE A FUNCTION OF LUMINOSITY Mandelbaum et al 2009

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

DETECTING DARK MATTER

Anti-proton spectrum

CONCLUSIONS The distribution of DM halos around galaxies shows a striking and complex phenomenology. This leads to essential information on: the very nature of dark matter the galaxy formation process Baryon +DM Simulations should eventually reproduce Shallow DM inner distribution, the observed relationships between the halo mass and 1) central halo density, 2) baryonic mass, 3) half-mass baryonic radius and 4) baryonic central surface density, a constant central halo surface density. Theory, phenomenology, simulations, experiments should play a balanced role in the search for dark matter and its role.