Probing Galaxy Halos with Tidal Interactions. Kyoto University Astronomy Department June 27, 2013

Transcription

1 Probing Galaxy Halos with Tidal Interactions Kyoto University Astronomy Department June 27, 2013

2 Galaxy Formation Baryons cool & collapse in dark halo potentials. White & Rees 78

3 Galaxy Formation Baryons cool & collapse in dark halo potentials. White & Rees 78 Strong feedback stops premature cooling. WR78, etc.

4 Galaxy Formation Baryons cool & collapse in dark halo potentials. White & Rees 78 Strong feedback stops premature cooling. WR78, etc. Halo spin sets disk scale. Fall & Efstathiou 80; Mo, Mao, & White 98

5 Galaxy Formation Baryons cool & collapse in dark halo potentials. White & Rees 78 Strong feedback stops premature cooling. WR78, etc. Halo spin sets disk scale. Fall & Efstathiou 80; Mo, Mao, & White 98 OR: Cold flows inject baryons and angular momentum. Dekel et al 09

6 Unresolved Issues Dwarf galaxies are less common than predicted. Some halos don t have the expected power-law cusps. How are halo and stellar mass related? What governs the angular momentum of disks? Do baryons modify dark halos?

7 Can Tails Constrain Dark Halos? As the mass and extent of the dark halo increase, tidal tails become shorter, less massive, and less striking, even under the most favorable conditions. Dubinski, Mihos, & Hernquist 96 f ' 0.03 f ' 0.06 f ' 0.11 f ' 0.19 time Dubinski, Mihos, & Hernquist (1996)

8 f ' 0.05 The ratio of the circular velocity to the escape speed correlates well with the tidal response. f ' E ' 7.2 f ' 0.09 E apple ve (R) v c (R) 2 f ' E ' 6.5 f ' 0.17 Long tails constrain potential well depth, not halo mass itself. Barnes 99 These constraints are potentially very powerful if dynamical modeling is combined with detailed observation. Springel & White 99 f ' E ' 5.1

9 Modeling Galactic Encounters Y V X X Find collisions of two normal spirals which reproduce the morphology and kinematics of an interacting system. Y V Y X

10 Modeling Galactic Encounters Y V X X Find collisions of two normal spirals which reproduce the morphology and kinematics of an interacting system. Y V Y X

11 NGC 4676: The Mice "The Mice": Colliding Galaxies NGC 4676: True-Color RGB Image

12 NGC 4676: The Mice

13 NGC 4676: The Mice

14 Encounter and Viewing Parameters Orbit p,e,µ 3 Disk Angles i 1,f 1,i 2,f 2 4 Time t 1 View q X,q Y,q Z 3 L,V Scale 2 Center X c,y c,v c 3 Total 16 This does not include the parameters for the initial galaxies!

15 NGC 4676: Parameter Correlations

16 NGC 4676: Time Scales

17 Galaxy Models: Construction Halo: NFW profile with smooth taper. h (r) / 8 < : r 1 (r + a h ) 2, r apple b h C h r e r/a h, r > b h Disk: exponential isothermal profile. d (R, z) / e R sech 2 (z/z d ) Bulge: steep-cusp profile (Jaffe 83). b (r) / r 2 (r + a b ) 2

18 Galaxy Models: Parameters 1. Stellar fraction (disk + bulge) f (M d + M b )/(M d + M b + M h )=0.2, 0.1, Halo concentration c b h /a h =4, 8, Halo:Disk scale ratio a h =1.2, 1.5, 1.875, 2.4, 3.0, 3.75, 4.8, Bulge (optional) a b /a h =0.16 M b /M d =1/3

19 Models without Bulges c = 16 f =0.2, c=8 c =4 c = 16 f =0.1, c=8 c =4 c = 16 f =0.05, c=8 c =4 ah =6.0 ah =4.8 ah =3.75 ah =3.0 ah =2.4 ah =1.875 ah =1.5 ah =1.2

20 Models with Bulges c = 16 f =0.2, c=8 c =4 c = 16 f =0.1, c=8 c =4 c = 16 f =0.05, c=8 c =4 ah =6.0 ah =4.8 ah =3.75 ah =3.0 ah =2.4 ah =1.875 ah =1.5 ah =1.2

21 Bar Instability f =0.1 c =4 a h =3.75 bulge f =0.2 c =4 a h =3.75 bulge Detect by measuring moment of inertia within 25%, 50%, 75% radii.

22 Stability Tests (Models w/o Bulges) c = 16 f =0.2, c=8 c =4 c = 16 f =0.1, c=8 c =4 c = 16 f =0.05, c=8 c =4 ah =6.0 ah =4.8 ah =3.75 ah =3.0 ah =2.4 ah =1.875 ah =1.5 ah =1.2

23 Stability Tests (Models w/ Bulges) c = 16 f =0.2, c=8 c =4 c = 16 f =0.1, c=8 c =4 c = 16 f =0.05, c=8 c =4 ah =6.0 ah =4.8 ah =3.75 ah =3.0 ah =2.4 ah =1.875 ah =1.5 ah =1.2

24 Encounter Survey Common parameters: Orbital eccentricity: e =0 (parabolic) Pericentric separation: p =2a h Disk angles: (i 1, 1) =(0, 0) (i 2, 2) = (71, 60) With bulges 27 experiments sampling range of stable models. Without bulges 5 experiments matching runs with bulges.

25 Encounter Survey (Models w/ Bulges) c = 16 f =0.2, c=8 c =4 c = 16 f =0.1, c=8 c =4 c = 16 f =0.05, c=8 c =4 ah =4.8 ah =3.75 ah =3.0 ah =2.4 ah =1.875 ah =1.5 ah =1.2

26 Encounter Survey (Models w/o Bulges) c = 16 f =0.2, c=8 c =4 c = 16 f =0.1, c=8 c =4 c = 16 f =0.05, c=8 c =4 ah =4.8 ah =3.75 ah =3.0 ah =2.4 ah =1.875 ah =1.5 ah =1.2

27 Legacy Model c = 16 f =0.2, c=8 c =4 c = 16 f =0.1, c=8 c =4 c = 16 f =0.05, c=8 c =4 ah =4.8 ah =3.75 ah =3.0 ah =2.4 ah =1.875 ah =1.5 ah =1.2

28 c = 16 f =0.2, c=8 c =4 c = 16 f =0.1, c=8 c =4 c = 16 f =0.05, c=8 c =4 ah =4.8 ah =3.75 ah =3.0 ah =2.4 ah =1.875 ah =1.5 ah =1.2

29 c = 16 f =0.2, c=8 c =4 c = 16 f =0.1, c=8 c =4 c = 16 f =0.05, c=8 c =4 ah =4.8 ah =3.75 ah =3.0 ah =2.4 ah =1.875 ah =1.5 ah =1.2

30 c = 16 f =0.2, c=8 c =4 c = 16 f =0.1, c=8 c =4 c = 16 f =0.05, c=8 c =4 ah =4.8 ah =3.75 ah =3.0 ah =2.4 ah =1.875 ah =1.5 ah =1.2

31 Quantifying Tidal Response Define disk material which reaches a distance from its parent galaxy d>10 1 as belonging to a tidal feature (cf SW99). f tidal M tidal /M d Feature classification measure two angles: Particle at Apocenter Companion at Pericenter cos P < 0 cos P > 0 cos a < 0 tail tail a cos a > 0 ambig bridge P

32 f =0.2, c =4, a h =3

33 f =0.1, c =4, a h =1.875

34 f =0.1, c =4, a h =1.875 d>6 1

35 f =0.1, c = 16, a h =3.75

36 Tidal Response: Correlations

37 Escape Parameters SW99 correlate tidal response with the ratio of escape to circular velocity, using apple ve (R) 2 E v c (R) evaluated at R =2 1 I prefer an equivalent parameter: v c(r) p 2 (R) = r 2 E Note that for Keplerian rotation, and for galaxies. =1 < 1

38 Tidal Response vs Escape Parameter

39 Results Compared Springel & White (1999)

40 Comparing Tidal Morphology f =0.1 c =4 a h =3 t = A ij A ij B ij + C f =0.1 c =8 a h =3 t = B ij r.a.d. P ij A ij B ij P ij A ij + B ij

41 Comparing Tidal Morphology f =0.1 c =4 a h =3 t = A ij A ij B ij + C f =0.1 c =8 a h =2.4 t =2.75 B ij r.a.d. P ij A ij B ij P ij A ij + B ij

42 Finding Good Matches f =0.1, c =4, a h =3 t = f =0.1, c =8, a h =2.4

43 Best Matches: All Models w/ Bulges f =0.2 f =0.1 f =0.05

44 Morphological Equivalences c = 16 f =0.2, c=8 c =4 c = 16 f =0.1, c=8 c =4 c = 16 f =0.05, c=8 c =4 ah =4.8 ah =3.75 ah =3.0 ah =2.4 ah =1.875 ah =1.5 ah =1.2

45 Conclusions Escape parameter roughly correlated with tidal response (SW99). Bulges have little direct effect on tidal features (SW99). SW99 did not study bulge-stabilized galaxies, and somewhat underestimated halo effects in limiting tidal tails. Bridges (tails) dominate tidal response at low (high) inclination. Halo concentration and disk scale appear degenerate. Next Model-matching with a range of galaxy models.

46 Thank You!