What are the best constraints on theories from galaxy dynamics?

Transcription

1 What are the best constraints on theories from galaxy dynamics? TDG in MOND DM MOND Françoise Combes Observatoire de Paris Tuesday 29 June 2010 O.Tiret

2 Still most baryons are unidentified 6% in galaxies ; 3% in galaxy clusters as hot X-ray gas <18% in the Lyman-alpha forest (cosmic filaments) 5-10% in the WHIM (Warm-Hot Intergalactic Medium) K OVI lines 65% are not yet identified or localised! The maximum possible in galaxies: 10 x HI gas mass Even then 80% out of galaxies 2

3 MOND and the dark baryons Is MOND compatible with the existence of dark gas in galaxies? What fraction provides the best fit to the rotation curves? Fit of ~50 rotation curves, c=m(dark)/mhi Tiret & Combes 08, Milgrom 07 3

4 Degeneracy cold H2/a0 NGC 1560: fits with variation of a 0 ~ 1/(gas/HI) V 4 = a 0 GM Tiret & Combes

5 Our own Milky Way: Escape velocity Potential in the MONDian regime F( r ) = (GMa 0 ) 1/2 ln r ½ V esc2 = F ( - F( r ) no escape possible! But a galaxy is never totally isolated External field effect (EFE) Where g << g e << a 0 Keplerian dependence, with renormalization G Ga 0 /g e 5

6 Milky Way: effect from Andromeda Observations RAVE (Smith et al 2007) 498 < v esc < 608kms km/s g e = a 0 /100 RAVE Wu et al 2007 Simulations with the Besançon model of MW 6

7 EFE: precession Newton: no effect MOND: non-linear effect, gravitationnal torque and precession Violation of the strong equivalence principle Origin of Warps? (also Brada & Milgrom 2000, LMC/MW) 7

8 Dark matter in the MW disk, through HI flaring Kalberla et al 2007 The best fit model to account for the HI flaring is dark matter in the disk + DM ring (15-17kpc) M ~ Mo

9 Dark matter rings? DMA? (dark matter annhihilation) Or baryons? De Boer et al 2005, from g-rays Disrupted dwarf satellites Since they possess DM, the DM could also follow streams MOND rings? (Milgrom & Sanders 9 08)

10 Phantom dark matter PDM MOND forces could be interpreted in terms of Newtonion force +DM r PDM = DF MOND /4pG - r vis r PDM can be negative 10

11 Orbit of the LMC (Large Magellanic Cloud) Recent proper motions measurements with HST Reveal that the velocity of the LMC is 378km/s (SMC 302km/s) Kallivayalil et al 2006, Piatek et al km/s higher than before, close to escape First passage of LMC+SMC Origin of the Magellanic Stream? Besla et al 2007 Tidal forces, or ram-pressure stripping? Efficiency? Ruzicka et al 2008, Mastropietro

12 Stability of galaxy disks spirals and bars are the motor of evolution CDM: Spheroidal haloes stabilise the disks MOND; disks are entirely self-gravitating However, the gravity law is not linear but in M 1/2 in the MOND regime Bars grow when angular momentum is transfered accepted by spheroidal haloes 12

13 Influence of DM halo With DM halo Without DM (MOND) Tiret & Combes

14 Bar strength and pattern speed with and w/o DM DM With DM, the bar appears later, and can reform after the peanut weakening through halo AM exchange, But Wb falls off Wb Tiret & Combes

15 Bar frequency Bar frequency Almost 80% of spiral galaxies are barred today without MOND no gas Bar strength 50 Statistics of bar strength Complex problem: the presence of gas destroys the bar, and gas accretion can form another bar DM without gas DM no gas Bar strength Bar frequency Bar frequency MOND with gas Bar strength MOND+gas with DM+gas Bar strength Bar strength DM, Sa MOND, Sa with gas without gas DM DM, Sb DM, Sc Sa Sb Sc Time (Gyr) MOND MOND, Sb MOND, Sc MOND compatible with observations 15

16 Resonant rings with MOND Now with gas Observations MOND Tiret & Combes 07 16

17 Peanut formation and evolution Angular momentum exchange with the DM halo DM MOND Simulations with stars only (no gas) The peanut moves in radius due to the slowing down of the bar 17

18 Interactions of galaxies: the Antennae: MOND versus CDM Dynamical friction is much lower with MOND: mergers last much longer CDM MOND Also much longer time-scale for merging of dissipationless galaxies (Nipoti et al 2007) 18

19 Merger induced starbursts degeneracy CDM: dynamical friction on DM particles very efficient mergers in one passage MOND: with the same angular momentum, merger will require many passages Starburst at each passage when minimal approach Number of "merger/sb" can be explained both ways Di Matteo et al

20 Simulations of the Antennae Degeneracy: starburst at each pericenter? Tidal tails can form at each pericenter, but much longer at the last one 20

21 Dynamical friction Analytically, with the small perturbations hypothesis, the dynamical friction is predicted stronger with MOND than in the equivalent Newtonian system with dark matter Ciotti & Binney 2004 (CB04), Nipoti et al 2008 However simulations show DF less efficient in galaxy interactions In CDM, a lot of particles acquire E and AM, and DF concept applicable In MOND, a small number of particles in the outer parts acquire big quantities (no analytical treatment) Nipoti et al 2007, Tiret & Combes

22 Globular clusters in dwarfs, wide binaries.. Globular clusters in dwarf galaxies should spiral inwards in a Hubble time in CDM The existence in Fornax of 5 GC without any stellar nuclear cluster is a challenge for both CDM and MOND (Sanchez-Salcedo et al 06) Exitence of wide-binaries of stars in dwarf spheroidal is also a challenge for CDM models They should have tighten due to dynamical friction againt CDM particles (Hernandez & Lee 2008) 22

23 DF in wide binaries A challenge for CDM -dr/dt (pc/myr) DM density around a star < 10 Gyr Log (Radius of binary, pc) Radius (pc) Compute for 1Mo/pc 3 of DM And DV = 5km/s Hernandez & Lee 08 23

24 DM in Globular Clusters themselves? MOND radius Scarpa & Falomo 2010 Velocity dispersions in the outer parts converge towards a constant The best GC analysed (wcen are suspect to be dwarf galaxies Others have EFE effects? Pal 14 compatible with MOND (Gentile et al 2010) 24

25 Formation of Tidal Dwarf Galaxies Exchange of AM is within the disk: much easier with MOND to form TDG In DM, requires very extended DM distribution (Bournaud et al 03) 25

26 TDG in N5291 HI ring Head-on collision simulation Bournaud et al

27 Dynamics of the TDGs With MOND, Gentile et al 2007 All inclinations= 45, from simulations (Bournaud et al 07) dark H 2 27

28 Compatible also with no DM In fact, the inclination could be more edge-on (65-90 ) The radial HI distribution is unknown If 45, either cold H2, or MOND can explain (Milgrom 07) TDG rotation curves accounted for without any DM 28

29 Dark matter in Ellipticals Planetary Nebulae: Romanowsky et al 2003 Dearth of dark matter??.. Visible matter (isotropic) isothermal (isotropic) 29

30 Anisotropy of velocities = 1 s 2 q/s 2 r, -, 0, 1 circular, isotropic and radial orbits Radius The observation of the velocity profile is somewhat degenerate and cannot lead to the dark matter content univocally 30

31 Dwarf spheroidals: degeneracy without proper motions

32 SIM: 200 velocities in 3D Strigari et al 2007

33 DM profile from satellites SDSS, 2500 deg 2, 3000 satellites Mb=-16, -18 (galaxies 14) Removal of interlopers s v =120km/s at 20kpc and 60km/s at 350kpc (Prada et al 2003) Declines agree with r ~r -3 of NFW (CDM profile) s v within 100kpc varies as L 0.3, quite close to TF relation In average 2 satellites per galaxy, and 0.2 interlopers See also McKay et al (2002) s ~L 0.5 from 1225 SDSS satellites M 260 in agreement with lensing results But flat velocity dispersion recovered (as if r ~r -2 ) 33

34 Satellites in SDSS Klypin & Prada 2009 Statistical satellites Only 1 or 0 for each galaxy 34

35 Tiret et al 2007 Test of the SDSS satellites 2 types of CDM CDM1: NFW cusp CDM2: as required by rotation curves DV Km/s PN satellites Radius (kpc) 35

36 Tully Fisher Equivalent Asterisk: Lenses (Hoekstra et al 2002) s~l TF normal spirals (Verheijen 2001) 120kpc s~l kpc s~l 0.5 Prada et al (2003) 36

37 Conclusion Bars and disk stability: good tests, but degrees of freedom Pattern speed of the bars Galaxy interaction and merging: very different dynamical friction rate, and merging frequency Required: raise the degeneracy Tidal Dwarf Galaxies: very promising Wide binaries (or GC) in dwarf galaxies Dwarf spheroidals with SIM proper motions 37