Self-Interacting Dark Matter

Transcription

1 Self-Interacting Dark Matter James Bullock UC Irvine Garrison-Kimmel, Oñorbe et al.

2 Act I Motivations

3 Missing Satellites Problem (1999) Theory: N>>1000 Klypin et al. 1999; Moore et al. 1999; Kauffmann et al Observation: Nbright~10 dwarfs

4 Easy answer: only the biggest clumps have stars? Theory: N>>1000 Klypin et al Observation: Nbright~10 dwarfs

5 Does this actually work? Theory: N>>1000 Klypin et al Observation: Nbright~10 dwarfs

6 Too Big to Fail Problem (2011) Data: All bright MW dsphs (L>10 5 Lsun) Boylan-Kolchin, JSB, Kaplinghat 2011, 2012 Garrison-Kimmel et al Plotted: all halos with Vinfall > 30km/s ~15 are unaccounted for Where are these massive halos?

7 Problem Persists in Local Volume (best-fit hosts removed) (best-fit hosts removed) Garrison-Kimmel et al, 2014ab Kirby et al Conclusion: Lots more (>15) missing massive halos beyond MW/M31 virial radii.! Hard to appeal to environment as a solution to TBTF problem (c.f. Brooks & Zolotov 12)

8 Too Big to Fail Problem (2011) Data: All bright MW dsphs (L>10 5 Lsun) Why is this a big deal? 1. Mass measurements are robust - this is not about trying to measure slopes (cores vs cusps). It s a normalization problem. 2. No reason these big halos should not be forming stars. Models predict they should! 3. Galaxies of concern have very low stellar mass content (M*<10 7 Msun). Probably not enough energy available for feedback lower densities Boylan-Kolchin, JSB, Kaplinghat 2011, 2012 Garrison-Kimmel et al Governato et al. 2012; Penarrubia et al. 2012; Garrison-Kimmel et al. 2013; Madau et al. 2014; etc.

9 Most Plausible Solution Data: All bright MW dsphs (L>10 5 Lsun) Maybe Too Big to Fail halos ARE there, but something has made densities lower? Boylan-Kolchin, JSB, Kaplinghat 2011, 2012

10 LCDM Galaxy-Halo Relation Needed to Match Counts & Clustering Behroozi et al Abundance Matching Behroozi et al DM Halo Virial Mass (Msun)

11 LCDM Galaxy-Halo Relation Needed to Match Counts & Clustering Behroozi et al Abundance Matching does not match measured scaling relations DM Halo Virial Mass (Msun)

12 Observed Galaxy-Halo Relation For Disks (Tully Fisher) Tully Fisher: Data Abundance Matching: Theory See: Miller et al same z=0.5 Oh et al. 2011

13 Observed Galaxy-Halo Relation For Disks (Tully Fisher) Tully Fisher: Data Abundance Matching: Theory Oh et al Too Big to Fail halos: M*~10 6 Msun Vmax ~ 40 km/s Predict:~ 10 of these per Milky Way

14 Observed Galaxy-Halo Relation For Disks (Tully Fisher) Tully Fisher: Missing Satellites halos: ~500 per Milky Way Data Abundance Matching: Theory Oh et al Too Big to Fail halos: M*~10 6 Msun Vmax ~ 40 km/s Predict:~ 10 of these per Milky Way

15 Evidence for Cored Density Profiles cuspy CDM halos M*~ Msun galaxies - Flores & Primack 1994; - Moore et al. 1994; - de Blok & Bosma 2002; - Kuzio de Narray et al. 2006, 2008; - etc. Data THINGS survey Oh, Brook, et al M*~ Msun galaxies -Walker & Penarrubia 2011; - Agnello & Evans (2012); - Amorisco et al. (2013); - etc.

16 Observed Galaxy-Halo Relation For Disks (Tully Fisher) Tully Fisher: Data Abundance Matching: Data Theory Too Dense Oh et al. 2011

17 Observed characteristic acceleration scale for galaxies Low Density missing mass High Density, no need for DM McGaugh 2014

18 Characteristic surface density for galaxies Donato et al. (2009)

19 Scattering rate: Self- interac,ng DM = dm m v rms For simplicity: Elastic, Velocity Independent, Isotropic Interesting things may happen when For τ ~ Gyr m 1cm2 /g Spergel & Steinhardt (2000); Kochanek & White (2000); Dave et al. 2001; Feng et al. (2009); Loeb & Weiner (2011); Vogelsberger et al. (2012),

20 Scattering rate: Consider: Self- interac,ng DM = dm m v rms and constant σ/m Characteristic: - acceleration scale - surface density

21 Scattering rate: Consider: Self- interac,ng DM = dm m v rms and constant σ/m Our simulations show a weak trend with halo mass

22 Act II Simulation Results

23 Plan 1. SIDM sims with constant σ/m - Galaxy: Vmax ~ 150 km/s (Milky Way scale) - Dwarf: Vmax ~ 40 km/s (Too Big to Fail Halo) - Cluster: Vmax ~ 1500 km/s (Constraints on σ/m?) 2. What about baryons? - Baryons matter for SIDM too - Coupling is significant, but potentially predictive - Might provide a way forward in explaining dark matter/baryon conspiracies

24 Λ+CDM Rocha et al Λ+SIDM 2 σ/m = 1 cm /g

25 SIDM: Rounder, lower- density cores. (substructure counts minimally affected) Λ+CDM Rocha et al Λ+SIDM 2 σ/m = 1 cm /g

26 SIDM Makes Low-Density, Cored Halos Density Cold Dark Matter SIDM: σ/m=1cm 2 /g Rocha et al radius

27 SIDM Makes Low-Density, Cored Halos Density Cold Dark Matter Velocity Dispersion SIDM: σ/m=1cm 2 /g SIDM: σ/m=1cm 2 /g Cold Dark Matter Rocha et al radius radius

28 How SIDM Halos Evolve Velocity Dispersion start heat flow Radius

29 How SIDM Halos Evolve isothermal constant density core! later (quasi-stable) Velocity Dispersion start heat flow Radius

30 How SIDM Halos Evolve unstable start Velocity Dispersion heat flow Radius

31 How SIDM Halos Evolve unstable start Velocity Dispersion soon core cools down - loses pressure support - collapses Radius

32 How SIDM Halos Evolve core collapse unstable start Velocity Dispersion heat flow soon core cools down - loses pressure support - collapses - heats up again - repeat Radius

33 Usually, this is what happens later (stable state) Velocity Dispersion start heat flow Radius

34 SIDM 1 Milky Way size halo Rocha et al CDM Milky Way size halo Substructure is about the same. SIDM rounder & less dense.

35 Fully cosmological zoom of isolated Milky Way: Vmax~150 km/s Cold Dark Matter SIDM: σ/m=1cm 2 /g Core properties (Burkert): * radius (kpc) 100 *

36 Fully cosmological zoom of isolated Dwarf: Vmax~ 40 km/s CDM! σ/m=0.5 cm 2 /g σ/m=1 cm 2 /g σ/m=10 cm 2 /g Elbert et al., in prep

37 Fully cosmological zoom of isolated Milky Way: Vmax~ 40 km/s Can solve Too Big To Fail: with σ/m > 0.5 cm 2 /g CDM! σ/m=0.5 cm 2 /g σ/m=1 cm 2 /g σ/m=10 cm 2 /g Elbert et al., in prep

38 Fully cosmological zoom of isolated Milky Way: Vmax~ 40 km/s Can solve Too Big To Fail: with σ/m > 0.5 cm 2 /g CDM! σ/m=0.5 cm 2 /g σ/m=1 cm 2 /g σ/m=10 cm 2 /g Have runs for σ/m=50 cm 2 /g that look OK at Vmax~30 km/s. - mild core collapse. - similar to σ/m=1cm 2 /g - hard to rule even this out! Elbert et al., in prep

39 Fully cosmological zoom of isolated Milky Way: Vmax~ 40 km/s CDM σ/m=1 cm 2 /g σ/m=10 cm 2 /g Elbert et al., in prep

40 Cosmological Sim of a Galaxy Cluster: Vmax~1500 km/s Mv=10 15 Msun CDM SIDM σ/m=0.1 cm 2 /g SIDM σ/m=0.5cm 2 /g SIDM σ/m=1cm 2 /g Rocha et al., in prep.

41 Cluster Shapes: death of SIDM greatly exaggerated CDM SIDM 0.1 SIDM 1 σ/m = 0 σ/m = 0.1 cm 2 /g σ/m = 1 cm 2 /g Miralda-Escude 2000: over-estimated the effect. ~ Peter et al. 2012

42 What about cluster densities?

43 Cosmological Sim of a Galaxy Cluster: Vmax~1500 km/s CDM SIDM σ/m=0.1 cm 2 /g ρcore ~ M sun /kpc 3 SIDM σ/m=0.5cm 2 /g SIDM σ/m=1cm 2 /g Rocha et al., in prep.

44 Newman et al. 2013

45 SIDM σ/m=0.5cm 2 /g 2 /g! ρcore SIDM SIDM SIDM SIDM SIDM Newman,Treu, Ellis, & Sand

46 SIDM σ/m=0.5cm 2 /g! ρ core ~ M sun /kpc 3 CDM SIDM CDM SIDM CDM (r=10 kpc) ρ(10kpc) ~ 10 7 M sun /kpc 3 CDM SIDM CDM SIDM CDM SIDM Newman,Treu, Ellis, & Sand

47 What Do Baryons Do??

48 Baryonic Contraction Elbert et al., in prep CDM (no galaxy) 20 kpc SIDM (no galaxy) 20 kpc

49 Baryonic Contraction Elbert et al., in prep CDM (no galaxy) 20 kpc SIDM (no galaxy) Grow MW disk potential 20 kpc

50 CDM (no galaxy) Baryonic Contraction Elbert et al., in prep CDM 20 kpc SIDM (no galaxy) Grow MW disk potential SIDM 20 kpc

51 Shape of SIDM halos very much altered by baryons (more so than even CDM)! Halo shape constraints on SIDM become much more difficult! SIDM seems to couple more tightly to galaxy potential than CDM (potentially testable observationally) Baryonic Contraction Grow MW disk potential See also: Kaplinghat et al Elbert et al., in prep CDM SIDM

52 Baryonic Contraction Elbert et al., in prep CDM Dense Galactic Center in both cases SIDM See also: Kaplinghat et al. 2013

53 SIDM + baryons CDM + baryons Density [M /pc 3 ] no galaxy 0 Gyr Solid: SIDM 10 Gyr 3 kpc Dash: 10 Gyr CDM 6 kpc 10 Gyr 1.5 kpc 10 Gyr no disk 10 4 Elbert et al., in preparation Radius [pc] See also: Kaplinghat et al. 2013

54 SIDM + baryons CDM + baryons Density [M /pc 3 ] no galaxy galaxy 0 Gyr Solid: SIDM 10 Gyr 3 kpc Dash: 10 Gyr CDM 6 kpc 10 Gyr 1.5 kpc 10 Gyr no disk Elbert et al., in preparation Radius [pc]

55 SIDM + baryons CDM + baryons Density [M /pc 3 ] galaxy 0 Gyr Solid: SIDM 10 Gyr 3 kpc Dash: 10 Gyr CDM 6 kpc 10 Gyr 1.5 kpc 10 Gyr no disk 10 4 Elbert et al., in preparation Radius [pc]

56 SIDM + baryons CDM + baryons Density [M /pc 3 ] light galaxy (LSB) galaxy 0 Gyr Solid: SIDM 10 Gyr 3 kpc Dash: 10 Gyr CDM 6 kpc 10 Gyr 1.5 kpc 10 Gyr no disk 10 4 Elbert et al., in preparation Radius [pc]

57 SIDM + baryons CDM + baryons Density [M /pc 3 ] dense galaxy galaxy light galaxy (LSB) 0 Gyr Solid: SIDM 10 Gyr 3 kpc Dash: 10 Gyr CDM 6 kpc 10 Gyr 1.5 kpc 10 Gyr no disk 10 4 Elbert et al., in preparation Radius [pc]

58 SIDM + baryons CDM + baryons Density [M /pc 3 ] dense galaxy light galaxy (LSB) galaxy dense galaxy infall produces some core collapse 0 Gyr Solid: SIDM 10 Gyr 3 kpc Dash: 10 Gyr CDM 6 kpc 10 Gyr 1.5 kpc 10 Gyr no disk 10 4 Elbert et al., in preparation Radius [pc]

59 SIDM + baryons CDM + baryons Density [M /pc 3 ] dense galaxy galaxy light galaxy (LSB) 0 Gyr Solid: SIDM 10 Gyr 3 kpc Dash: 10 Gyr CDM 6 kpc 10 Gyr 1.5 kpc 10 Gyr no disk Dense galaxy: SIDM halos are denser than CDM LSB galaxy: SIDM halos are less dense than CDM 10 4 Elbert et al., in preparation Radius [pc]

60

61 Ways forward with SIDM σ/m at V~1000 km/s σ/m at V~100 km/s σ/m at V~10 km/s

62 Ways forward with SIDM σ/m at V~1000 km/s σ/m at V~100 km/s σ/m at V~10 km/s Cluster Shapes? - uncertain role of baryons shape constraints very hard - c.f. Kaplinghat et al. 2013; Elbert et al., in prep. Cluster Mergers? - Yes! Stay tuned, but don t believe published constraints - σ/m < 10 cm 2 /g? Will Dawson + Stacy Kim +. UC Davis, Ohio State, UC Irvine, Caltech/JPL, Harvard

63 Ways forward with SIDM σ/m at V~1000 km/s σ/m at V~100 km/s σ/m at V~10 km/s Core Densities, Shapes, etc. HARD for systems at V ~100 km/s - Very hard regime because of uncertain role of baryons - Need to do more realistic simulations SIDM (no galaxy) SIDM

64 Ways forward with SIDM σ/m at V~1000 km/s σ/m at V~100 km/s σ/m at V~10 km/s Smallest DM-dominated dwarfs V~10 km/s remain great laboratories - TBTF solved for σ/m = cm 2 /g - Core sizes/densities possibly prefer σ/m ~ 1 cm 2 /g - Need more statistics - Role of feedback in affecting SIDM densities needs work

65 End. Thanks.

66

67 Observed Galaxy-Halo Relation For Disks (Tully Fisher) Tully Fisher: Sarah Miller et al z~1 Data Abundance Matching: Theory Too Dense