Dark Matter and/or MOND in Giant Ellipticals

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1 Dark Matter and/or MOND in Giant Ellipticals NGC 4636 & NGC 1399 Ylva Schuberth Tom Richtler, Michael Hilker, Boris Dirsch 1 July 2010 / Strasbourg Y. Schuberth (AIfA) Strasbourg 1 / 16

2 Outline 1 Globular Clusters as Dynamical Tracers 2 Jeans Models 3 NGC 1399 & NGC NGC 4636 and MOND 5 NGC 1399 and MOND 6 Conclusions & Questions Y. Schuberth (AIfA) Strasbourg 2 / 16

3 Globular Clusters as Dynamical Tracers Traditional Tracers in Giant Ellipticals No neutral gas no HI 21 cm rotation curves No ongoing star formation no Hα rotation curves High central surface brightness optical spectroscopy BUT limited to the central parts (steep luminosity proles) Y. Schuberth (AIfA) Strasbourg 3 / 16

4 Globular Clusters as Dynamical Tracers Traditional Tracers in Giant Ellipticals No neutral gas no HI 21 cm rotation curves No ongoing star formation no Hα rotation curves High central surface brightness optical spectroscopy BUT limited to the central parts (steep luminosity proles) Discrete Dynamical Tracers Planetary Nebulae (PNe) Globular Clusters (GCs) Y. Schuberth (AIfA) Strasbourg 3 / 16

5 Globular Clusters as Dynamical Tracers Traditional Tracers in Giant Ellipticals No neutral gas no HI 21 cm rotation curves No ongoing star formation no Hα rotation curves High central surface brightness optical spectroscopy BUT limited to the central parts (steep luminosity proles) Discrete Dynamical Tracers Planetary Nebulae (PNe) Globular Clusters (GCs) Aim: Use observed σ los (R) to obtain mass prole from Jeans models Comparison to Xray based mass estimates But: Large number of velocities required to obtain σ los (R) Y. Schuberth (AIfA) Strasbourg 3 / 16

6 Globular Clusters as Dynamical Tracers Globular Cluster Systems of Giant Ellipticals Large numbers of GCs (up to 10 4 ) Spatially extended systems Bimodal colour distribution predominantly old stellar populations two subpopulations with dierent metallicities: blue (metalpoor) & red (metalrich) GCs Y. Schuberth (AIfA) Strasbourg 4 / 16

7 Globular Clusters as Dynamical Tracers Globular Cluster Systems of Giant Ellipticals Large numbers of GCs (up to 10 4 ) Spatially extended systems Bimodal colour distribution predominantly old stellar populations two subpopulations with dierent metallicities: blue (metalpoor) & red (metalrich) GCs Blue GCs spatially more extended higher velocity dispersion Red GCs more concentrated towards host galaxy lower velocity dispersion Y. Schuberth (AIfA) Strasbourg 4 / 16

8 Globular Clusters as Dynamical Tracers Observational Methods 1 Wideeld Photometry Galaxy luminosity prole GC number density proles (for both populations) Candidate selection for spectroscopy 2 Long slit spectroscopy Galaxy velocity dispersion prole Υ 3 Multiobject spectroscopy with masks GC velocities Y. Schuberth (AIfA) Strasbourg 5 / 16

9 Jeans Models The spherical nonrotating Jeans Equation: d ( l(r) σr(r) 2 ) + 2 β(r) l(r) σ 2 dr r r(r) = l(r) G M(r) r 2 l(r) spatial distribution of tracer population σ(r) radial velocity dispersion. β(r) anisotropy parameter. β 1 σ θ 2 σ 2 r M(r) total enclosed mass (M(r) = M + M dark ) Y. Schuberth (AIfA) Strasbourg 6 / 16

10 Jeans Models The LineofSight Velocity Dispersion For constant β, the solution to the Jeans Eqn. reads: l(r) σ 2 r(r) = G R r l(r ) M(r ) 1 r 2 ( ) r 2β dr. The projected velocity dispersion is given by: [ N(R) σlos 2 (R) = 2 lσr 2 r r 2 R dr β lσ 2 ] 2 R2 r r r 2 R dr. 2 Mass Anisotropy Degeneracy The prole σ los (R) can be nearly invariant between changes in the mass prole M(r) and the anisotropy parameter β(r). R r Y. Schuberth (AIfA) Strasbourg 7 / 16

11 NGC 1399 & NGC 4636 NGC 1399: Centre of Fornax (D 19 Mpc) NGC 4636: Outskirts of Virgo (D 17.5 Mpc) (DSS images: kpc) Y. Schuberth (AIfA) Strasbourg 8 / 16

12 NGC 1399 & NGC 4636 NGC 1399: 1 Xrays Ikebe et al. (1996) Paolillo et al. (2002) 2 Photometry Dirsch et al. (2003) 3 GC dynamics Richtler et al. (2004) (468 GC velocities) Richtler et al. (2008) MOND Schuberth et al. (2010a) (700 GC velocities) NGC 4636: 1 Xrays Jones et al. (2002) Loewenstein & Mushotzky (2003) Johnson et al. (2009) 2 Photometry Dirsch et al. (2005) 3 GC dynamics Schuberth et al. (2006) (172 GC velocities) Schuberth et al. (2010b) (460 GC velocities) Y. Schuberth (AIfA) Strasbourg 9 / 16

13 NGC 1399 & NGC 4636 NGC 1399: At centre of Fornax cluster Very extended GC system ( 250 kpc) Complex Xray halo morphology `nested' DM halo? Y. Schuberth (AIfA) Strasbourg 10 / 16

14 NGC 1399 & NGC 4636 NGC 1399: At centre of Fornax cluster Very extended GC system ( 250 kpc) Complex Xray halo morphology `nested' DM halo? GC results No signs for `onset' of Fornax cluster DM halo component NGC 1399 blue GC population `contaminated' by GCs stripped from neighbours Y. Schuberth (AIfA) Strasbourg 10 / 16

15 NGC 1399 & NGC 4636 NGC 1399: At centre of Fornax cluster Very extended GC system ( 250 kpc) Complex Xray halo morphology `nested' DM halo? NGC 4636: In low density environment Very rich GC system Very Xray bright: extremely DM dominated?? GC results No signs for `onset' of Fornax cluster DM halo component NGC 1399 blue GC population `contaminated' by GCs stripped from neighbours Y. Schuberth (AIfA) Strasbourg 10 / 16

16 NGC 1399 & NGC 4636 NGC 1399: At centre of Fornax cluster Very extended GC system ( 250 kpc) Complex Xray halo morphology `nested' DM halo? GC results No signs for `onset' of Fornax cluster DM halo component NGC 1399 blue GC population `contaminated' by GCs stripped from neighbours NGC 4636: In low density environment Very rich GC system Very Xray bright: extremely DM dominated?? GC results Missing mass problem. But not as severe as claimed in Xray studies With Xray abundance gradient: results agree Only 2 bright, blue GCs have `odd' velocities Y. Schuberth (AIfA) Strasbourg 10 / 16

17 NGC 1399 & NGC 4636 NGC 1399: GC velocities NGC 4636: GC velocities (GCs in vicinity of NGC 1404 removed) ( kpc) Y. Schuberth (AIfA) Strasbourg 11 / 16

18 NGC 4636 Mass proles NGC Isotropic models: β = 0 V circ [km s 1 ] MOND (Fraternali et al.) MOND (Famaey & Binney) NFW Burkert Stars (Newtonian) R [kpc] Stellar M/L: Υ,R = 5.8 NFW: r s = 100 kpc, ϱ s = M pc 3 Burkert halo: r 0 = 10 kpc, ϱ 0 = M pc 3 Y. Schuberth (AIfA) Strasbourg 12 / 16

19 NGC 4636 Mass proles σ los [km s 1 ] Stars NGC 4636 MOND NFW Burkert Stars (Newtonian) R [kpc] Blue GCs Isotropic models: β = 0 Stellar M/L: Υ,R = 5.8 NFW: r s = 100 kpc, ϱ s = M pc 3 Burkert halo: r 0 = 10 kpc, ϱ 0 = M pc 3 Y. Schuberth (AIfA) Strasbourg 12 / 16

20 NGC 1399 Mass proles NGC Isotropic models: β = V circ [km s 1 ] Richtler '08 NFW (red GCs & stars) McNeil (2010): PNe MOND Fraternali et al MOND Famaey & Binney Stars (Newtonian) R [kpc] Stellar M/L: Υ,R = 5.5 NFW (Richtler et al. 08): r s = 50 kpc, ϱ s = M pc 3 NFW (Red GCs & stars): r s = 30 kpc, ϱ s = M pc 3 Y. Schuberth (AIfA) Strasbourg 13 / 16

21 NGC 1399 Mass proles NGC Isotropic models: β = V circ [km s 1 ] Richtler '08 NFW (red GCs & stars) McNeil (2010): PNe MOND Fraternali et al MOND Famaey & Binney Stars (Newtonian) R [kpc] Stellar M/L: Υ,R = 5.5 NFW (Richtler et al. 08): r s = 50 kpc, ϱ s = M pc 3 NFW (Red GCs & stars): r s = 30 kpc, ϱ s = M pc 3 Y. Schuberth (AIfA) Strasbourg 13 / 16

22 NGC 1399 Mass proles NGC Isotropic models: β = V circ [km s 1 ] Richtler '08 NFW (red GCs & stars) McNeil (2010): PNe MOND Fraternali et al MOND Famaey & Binney Stars (Newtonian) R [kpc] Stellar M/L: Υ,R = 5.5 NFW (Richtler et al. 08): r s = 50 kpc, ϱ s = M pc 3 NFW (Red GCs & stars): r s = 30 kpc, ϱ s = M pc 3 Y. Schuberth (AIfA) Strasbourg 13 / 16

23 NGC 1399 Mass proles 500 NGC 1399 Isotropic models: β = Stellar M/L: Υ,R = 5.5 V circ [km s 1 ] Richtler '08 NFW (red GCs & stars) McNeil (2010): PNe MOND Fraternali et al MOND Famaey & Binney Stars (Newtonian) R [kpc] NFW (Richtler et al. 08): r s = 50 kpc, ϱ s = M pc 3 NFW (Red GCs & stars): r s = 30 kpc, ϱ s = M pc 3 Y. Schuberth (AIfA) Strasbourg 13 / 16

24 Conclusions NGC 4636 appears to be MONDian NGC 1399 might be MONDian, mass models strongly depend on the treatment of 'interlopers' in the velocity data. More detailed modelling required, including dierent choices for µ(x) Y. Schuberth (AIfA) Strasbourg 14 / 16

25 Question(s):Truncated dynamically hot systems? NGC 4636: GC number density drops o at 40 kpc [Dirsch et al. 2005] NGC 1399 Xray halo: 3 components, β models have extreme exponents [ Paolillo et al. (2002) & Scharf et al. (2005)] Y. Schuberth (AIfA) Strasbourg 15 / 16

26 Thank You! Y. Schuberth (AIfA) Strasbourg 16 / 16