Dark Matter in Dwarf Galaxies

Transcription

1 Maryland Center for Fundamental Physics & Joint Space-Science Institute May 2010 Advances in Theoretical and Observational Cosmology Dark Matter in Dwarf Galaxies Stacy McGaugh University of Maryland

2 Maryland Center for Fundamental Physics & Joint Space-Science Institute May 2010 Advances in Theoretical and Observational Cosmology Collaborators Rachel Kuzio de Naray (UCI) David Stark (UNC) Joe Wolf (UCI) Matthew Zagursky (Hawaii) Clemens Trachternach (R-U Bochum) Matt Walker (Cambridge) Rob Swaters (NOAO) Erwin de Blok (Cape Town) Jim Schombert (Oregon) Thijs van der Hulst (Groningen) Mario Mateo (Michigan) Ed Olzewski (Arizona) Bob Sanders (Groningen) R-J Dettmar (R-U Bochum)

3 Maryland Center for Fundamental Physics & Joint Space-Science Institute May 2010 Advances in Theoretical and Observational Cosmology Outline Dark Matter Distribution in Spirals and Dwarfs Baryonic Tully Fisher Relation (BTFR) & Halo Baryons Correlated Deviations from the BTFR among ultrafaints David St. Hubbins: It's such a fine line between stupid, and clever.

4 UGC 2885 NGC 2403 Leo I 100 kpc 10 kpc V c = 300 V c = 134 NGC DDO WLM 5 kpc 2 kpc 500 pc / σ 0 =9 M13 20 pc V c = 72 V c = 38 σ 0 =6

5 Rotation curves of spirals Rotation curves and late type disks (Sd, Sm, Irr) Kuzio de Naray et al. (2006, 2008, 2009); Trachternach et al. (2009)

6 Dynamical Figure mass-to-light 4b ratio within optical disk M/L increases as the characteristic system surface brightness decreases. McGaugh & de Blok (1998) There is a critical scale at which the mass discrepancy appears: Σ 1000 M pc 2 McGaugh (2004) Disk central surface brightness

7 NGC 2403 HSB UGC 128 LSB Same global Mb,V de Blok & McGaugh (1996) Tully & Verheijen (1997) Very different mass distributions

8

9 The halo-only rotation curves of all spirals are strikingly similar (McGaugh et al. 2007) ~600 resolved points from 60 galaxies with σv/v < 5% & R > 1 kpc. log V h = 1 2 log R ρ = R M pc 3 = 1.27 R GeV cm 3

10 The halo-only rotation curves of all spirals are strikingly similar (McGaugh et al. 2007) ~600 resolved points from 60 galaxies with σv/v < 5% & R > 1 kpc. log V h = 1 2 log R ρ = R M pc 3 = 1.27 R GeV cm 3

11 The halo-only rotation curves of all spirals are strikingly similar (McGaugh et al. 2007) ~600 resolved points from 60 galaxies with σv/v < 5% & R > 1 kpc. log V h = 1 2 log R ρ = R M pc 3 = 1.27 R GeV cm 3

12 observed ridge-line

13 Enclosed halo mass M = (200 M pc 2 )R 2 McGaugh et al. 2007

14 Enclosed halo mass M = (200 M pc 2 )R 2 Data are consistent with a [nearly] universal halo. Strigari et al. (2008) McGaugh et al. 2007

15 Strigari et al. (2008) M(300 pc) = M

16 Enclosed halo mass M = (200 M pc 2 )R 2 Data are consistent with a [nearly] universal halo. M(300 pc) = M Strigari et al. (2008) McGaugh et al. 2007

17 Enclosed halo mass M = (200 M pc 2 )R 2 Data are consistent with a [nearly] universal halo. Walker et al. (2010) MW dsph M31 dsph LSB disks Walker et al. (2009) Kalarai et al. (2009) Kuzio de Naray et al.

18 Walker et al. (2010) Velocity log V h = 1 2 log R Mass M = (200 M pc 2 )R 2 Acceleration g h 1 km 2 s 2 pc 1

19 Maryland Center for Fundamental Physics & Joint Space-Science Institute May 2010 Advances in Theoretical and Observational Cosmology Dark Matter Distribution in Spirals and Dwarfs Data are consistent with quasi-universal halo Unifies results of Strigari et al. (2008), Donato et al. (2009), & Gentile et al. (2009). All implicitly contained in McGaugh et al. (2007). Baryonic Tully Fisher Relation (BTFR) & Halo Baryons

20 Global Relation: Tully-Fisher Relation Stars only M =Υ L McGaugh (2005) Pizagno et al.

21 Global Relation: Baryonic Tully-Fisher Stars plus gas Mb = M + Mgas line: log M b = 4 log V f +1.7 (McGaugh 2005) Implies no other substantial reservoirs of baryonic mass.

22 Line-widths Bothun et al. (1985) Sakai et al. (2000) McGaugh et al. (2000) Gurovich et al. (2010) Trachternach et al. (2009)

23 Resolved rotation curves McGaugh (2005) Stark et al. (2009) Trachternach et al. (2009)

24 f*: stellar fraction residual form BTFR Anderson & Bregman (2010)

25 Spirals Clusters BTFR: M b = AVc 4 A = 45 ± 10 M km 4 s 4 Cluster data: Giodini et al. (2009) M = B V 3 B 500 = M km 3 s 3 Spiral data: McGaugh et al. (2005) gas disks Gas dominated disks: Stark et al. (2009) Trachternach et al. (2009) Local dwarfs Local dwarf data: Walker et al. (2009) M*/L as per Mateo et al. (1998) V c = 3σ McGaugh et al. (2010)

26 cosmic f b =0.17 f d = M b f b M 500 f = M f b M 500 Where are these baryons? Detected baryon fraction increases monotonically with mass Star formation peak conversion efficiency M M = 4π 3 ρ critr 3 M 500 = V for H 0 = 72 V c = f V V 500 ; assume f V =1.1 McGaugh et al. (2010)

27 Maryland Center for Fundamental Physics & Joint Space-Science Institute May 2010 Advances in Theoretical and Observational Cosmology Baryonic Tully Fisher Relation (BTFR) & Halo Baryons Disks obey BTFR with M b = AV 4 c Most halo baryons are missing Correlated Deviations from the BTFR among ultrafaints

28 Residuals of dwarf Spheroidals from Baryonic Tully-Fisher Relation McGaugh & Wolf (2010) gas disks Spirals Local dwarfs Classical dwarfs Ultrafaint dwarfs M31 dwarfs Leo T (contains gas) Local dwarf data: Wolf et al. (2010) Kalirai et al. (2009; M31) M*/L as per Mateo et al. (1998) & Martin et al. (2008) F b = M b AV 4 c

29 dsph BTFR residuals correlate with Luminosity Shape Size Distance ( r D ) 3 F T,D = M m Metallicity Tidal Susceptibility

30 Reinoization Does not simultaneously explain spirals Does not explain correlations of BTFR residuals

31 Dwarfs whose stars have little time to adjust to changes in the potential suffer the largest deviations and have more elliptical shapes. Suggests a role for tides.

32 Maryland Center for Fundamental Physics & Joint Space-Science Institute May 2010 Advances in Theoretical and Observational Cosmology Correlated Deviations from the BTFR among ultrafaints Deviations correlate with luminosity, size, [Fe/H], shape, distance, and tidal susceptibility Disfavors stochastic models - probably not just a cut-off from reionization or feedback Tides appear to play some role.