DARK MATTER IN GALAXIES

Paolo Salucci (SISSA)

Dennis: Rotation Curves, Dark Matter, Nature of, Role of Baryons.

Importance of the topics but low interest from Scientific Community

Persic, M., S. P., 1988, MNRAS, 234 131

Dark and visible matter in spiral galaxies

Persic, M.; S. P., Stel, F. 1996 MNRAS, 281, 27

The universal rotation curve of spiral galaxies - I. The dark matter connection

Gentile, G.; S. P., Klein, U. 2004 MNRAS, 351, 903

The cored distribution of dark matter in spiral galaxies

S.P + 2007 MNRAS

The universal rotation curve of spiral galaxies out the virial radius II

S.P. ...... ADS reviews

Central surface brightness vs magnitude

The Realm of Galaxies

15 mag range, 4 types, 16 mag arsec-2.range

Stellar distribution L(R/RD)/LT is independent of luminosity

The light surface profile I(r) = I0exp (-R/RD).

A mass lenght-scale

luminosity independent?

1000 objects

Colo

rs a

re r

ad

ially

con

stan

t

3RD

RTF: magnitude vs log velocity @ different radii xi RD, [ xi=0.5,1,…5]

3 samples (600, 89, 78) M =ai + bi log V(xi)

No relationship ↔ V does not trace the mass

Vmax

Does the kinematics probe the mass distribution of galaxies ? Yes.

• Radial Tully Fisher

• Inner mass distribution

0.0 0.5 1.0 1.5 2.0 2.5 3.0

0

50

100

150

200

250

V

R/Rd

UGC2405

Radial TF

Slope and scatter of the TF-relations:

MB = ai + bi log V(xi)

The slope increases from -4 to -8.

No change in slope ↔ no DM or a constant fraction of DM

The minimum scatter 0.2 mag at 2.2 RD

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0-1

-2

-3

-4

-5

-6

-7

-8

-9

86 galaxies (Courteau) 967 galaxies (Mathewson)

Slo

pe

R/Rd

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

86 galaxies (Courteau) 967 galaxies (Mathewson)

sca

tter

R/Rd

MODEL

V traces the potential

DM emerges at large radii

Modelling the very inner circular velocities: light traces the mass

Phenomenology of spiral kinematics

The rotation curves 3200 coadded individual

PSS

C+06

RC slopes vary among galaxies and within them.

They indicate the presence and the amount of dark matter.

At 3 disk length scales

The URC concept

➲ @ fixed L and x=R/RD, the Cosmic Variance of V(x,L) is one order of magnitude smaller than the variations that:

➲in each galaxy, V(x) shows as x varies.

➲V(x) shows, @ each x, in galaxies of different L

3.avi

../Desktop/3.avi

The URC

Rotation curve modelling.

V d is k R➲ : from I-band photometry

➲ : from HI observations

➲

• dark halos with constant density cores

• dark halos with “cusps” (NFW, Moore)

• HI-scaling

• MOdified Newtonian Dynamics

..t4bt5b

V h a lo R

V g a s R

V tot2 V DM

2 V disk2 V gas

2

NFW Halos

Burkert Halos

cored vs cusped

VNFW fits uniquely a rotation curve

Modelling the Universal Rotation Curve

rotation velocity

stellar contribution

dark matter contribution

Stars

DM

LM

A family governed by luminosity

DM

fra

ctio

n

core radiushalo central density

luminosity

The role of the slope of the RC

Halo central density vs core radius scaling r 0 =10-23 (r0 /kpc)-1 g/cm3

dSph

B

URCWL

Virial halo masses

andHMF M h dM h A M h

1.84 dM h

HMF M h dM h dM bdM b BMF M b dM b

Christiane Frigerio Martins

Weak lensing

With a density profile we model the tangential shear

Obtain the structural free parameters.

Same results as those obtained from RCs.

Burkert profile provides excellent fit, better than NFW.

NFW

B

DM halo density: observations vs simulations

URCL

NFW

URCH

The UNIVERSAL velocity CURVE

Dark halos from simulations

Halos form hierarchically bottom-up via grav. amplifications of initial density flucts. Most

evident property: CENTRAL CUSP

NFW r s

r r s 1 r r s2

M vir43 vir u Rvir

3cvir Rvir r s 9.7 M vir 1012 M un

0.09V vir

2 GM vir Rvir

cuspy NFW density profiles disagree with observed kinematics.

comparison galaxy by galaxy and of coadded kinematics.

The cusp vs core issue

NFW HALOS

• Fit badly the RCs

• Unphysically too low stellar mass-to-light ratios

• Unphysically too high halo masses

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A test case: ESO 116-G12

gas

stars

halo

Cored halos the best fits

50 objects investigated

NFW inconsistent

Theory Obis ssw

Obs Theory

DDO 47: a decisive case

NFW

Results fromTrieste: analysis of highquality RCs

URC fits to RCs

DDO 47

Borriello & Salucci, MNRAS 323, 285 (2001)

Gentile, Tonini & Salucci, A&A 467, 925 (2007)Gentile et al., ApJ 634, L145 (2005)

DDO 47: non circular motions?

R

V (

min

or a

xis)

Triaxial halos predictions

A Universal Mass Profile Walker et al 09Dwarf Spheroidal Galaxies

LCDM Universal Rotation Curve from NFW profile and MMW theory

➲ AN INTRIGUING PROPERTY

A matter enigma

DM in early-types: weak+strong lensingDM in early-types: weak+strong lensing22 bright E/S0s at z ~ 0.2 (SLACS: Gavazzi et al. 2007)

DARK MATTER IS PRESENT IN GALAXIES

IT IS STRONGLY RELATED TO THE LUMINOUS MATTER

THERE IS A SOLID EMPIRICAL SCENARIO

We can uniquely mass model a RC

disk-halo components, known surf phot, reliable V(R) and dV/dR, resolution ~ 0.3 RD

A way out? angular momentum exchange between baryons and DM Tonini Lapi Salucci

cusp

core