Where to Look for Dark Matter Weirdness

Where to Look for Dark Matter Weirdness Dark Matter in Southern California (DaMaSC) - II James Bullock UC Irvine Garrison-Kimmel, Oñorbe et al.

Collaborators Mike Boylan-Kolchin U. Maryland Miguel Rocha Shea Garrison-Kimmel Oliver Elbert Manoj Kaplinghat Annika Peter The Ohio Sate University Jose Oñorbe MPIA Heidelberg

Outline 1. Dwarf Galaxies and the Too Big to Fail Problem 2. Baryon Physics vs. Dark Matter Physics - SIDM with σ/m ~ (0.5-1) cm 2 /g can solve the problem - Feedback probably can t solve it, environment an issue. 3. Baryons + SIDM = Harder than we hoped (but fun) 4. Future directions

Smallest Dwarfs: Great DM Laboratories M? 10 6 M r? 500pc M DM M? 50 Dark Matter Dominated => Easy to interpret Very Few Stars => SN Can t Alter DM

Best-studied dwarfs are satellites of MW Simulated MW Halo Bright Satellites of the MW L>10 5 Lsun Garrison-Kimmel, JSB, Boylan-Kolchin

Biggest subhalos = brightest satellites? Image: Garrison-Kimmel

How do the masses compare? Image: Garrison-Kimmel

All bright MW dsphs (L>10 5 Lsun) 8 biggest subhalos (remove LMC/SMC analogs) 8 biggest subhalos are too dense to host ANY of MW dsph satellites Boylan-Kolchin, JSB, Kaplinghat 2011,2012

Too Big to Fail Problem 8 biggest subhalos (remove LMC/SMC analogs) 8 biggest subhalos are too dense to host ANY of MW dsph satellites Boylan-Kolchin, JSB, Kaplinghat 2011,2012

Summary of the Too Big To Fail problem: Boylan-Kolchin, JSB, Kaplinghat 2012 Expect 5-40 subhalos with Vmax >25 km/s (from 48 simulations) Garrison-Kimmel et al. in prep

Summary of the Too Big To Fail problem: Boylan-Kolchin, JSB, Kaplinghat 2012 Why nothing here? Expect 5-40 subhalos with Vmax >25 km/s (from 48 simulations) Garrison-Kimmel et al. in prep

What Can Baryons Do?? Consider a M* ~10 6 Msun dwarf galaxy What does it take to remove enough DM?

Basic Energy Argument Against SN Feedback M? 10 6 M M DM 5 10 7 M Must remove ~50 times more dark matter than mass in stars! Energy Required: > 10 55 ergs Exceeds every supernovae that has gone off coupled directly to the dark matter. Penarrubia et al. 2012; Garrison-Kimmel et al. 2013

Oñorbe et al. (in prep) Minimal change in DM density Jose Oñorbe Use P-GADGET SPH - Overcomes most standard SPH issues - Feedback of Hopkins, Quartaert, and Murray (2012) Dark Matter Only Full Hydrodynamics M* ~ 10 6 Msun Not converged numerically mdm = 1200Msun mgas = 250Msun ε dm = 40pc Z=0 Stats: Abundance Matching [GOOD] Fe/H ~ -2.5 [GOOD] Mgas/M* ~ 0.1 [OK]

Baryonic Feedback: Not so effective for M* < 10 7 Log slope density profile CORE Data CDM-only prediction Simulations with feedback CUSP Governato et al. 2012

Baryonic Feedback: Not so effective for M* < 10 7 CORE Log slope density profile M*< 10 7 Msun: very little change in DM prediction Data CDM-only prediction Simulations with feedback CUSP Governato et al. 2012

Is there a baryonic solution to Too Big to Fail? SN Feedback alone: No Why nothing here? - Not Enough Energy: hard to affect densities with < 10 6 Msun of stars (<10 4 SN) Garrison-Kimmel et al. 2013; Governato et al. 2012; Penarrubia et al. 2012 Environment: best bet - Tidal forces (extra from disk) and ram-pressure stripping provide additional sources of energy to remove DM Brooks & Zolotov 2012; Zolotov et al. 2012; Arraki et al. 2012

What s next? Extend these studies to the field (no ram-pressure or tides) Ferrero, Abadi,Navarro, Sales, & Gurovich 2012 - Examine rotation curves of field dwarfs with Mgal~10 6-7 Msun - Same problem: not dense enough - Hard to reconcile with DM halo mass function + observed lum function Abstract:... Resolving this challenge seems to require new insights into dwarf galaxy formation, or perhaps a radical revision of the prevailing paradigm.

Beyond Cold Dark Matter? Warm Dark Matter: Self-interacting Dark Matter: CDM WDM CDM SIDM Lovell et al. 2011 Vogelsberger et al. 2011 m dm kev /m dm 1cm 2 /g Lovell et al. 2011 Vogelsberger et al. 2011, 2012; Rocha et al. 2012; Peter et al. 2012; Spergel & Steinhardt (2000)

Simula'ng Self- interac'ng DM Scattering rate: = dm m v rms For now: Elastic, Velocity Independent, Isotropic Interesting things happen when H 0 m 1cm2 /g Miguel Rocha Annika Peter Manoj Kaplinghat

Rocha et al. 2012 IdenGcal large- scale structure Λ+CDM Λ+SIDM σ/m = 1 cm 2 /g

Rocha et al. 2012 Λ+CDM Λ+SIDM σ/m = 1 cm 2 /g

Rocha et al. 2012 SIDM: Rounder, lower- density cores. (substructure counts minimally affected) Λ+CDM Λ+SIDM σ/m = 1 cm 2 /g

Density Cold Dark Matter SIDM Makes Cored Halos SIDM: σ/m=1cm 2 /g Rocha et al. 2012 radius

SIDM Makes 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. 2012 radius radius Isothermal velocity profile creates core.

Fully cosmological zoom of isolated dwarf halo: Vmax~35km/s CDM SIDM: σ/m=0.5cm 2 /g SIDM: σ/m=1cm 2 /g SIDM: ~ 500 pc cores w/ densities ~0.1 Msun/pc 3 - Both values match dsph observations (Strigari et al. 08; Walker & Penarrubia 12) Mass resolution: 1200 Msun (DM) Force resolution: 40 pc Elbert et al., in preparation

SIDM with σ/m=(0.5-1)cm 2 /g Solves Too Big To Fail Problem SIDM: σ/m=0.5cm 2 /g CDM UrsMin Draco Leo I SIDM: σ/m=1cm 2 /g Elbert et al., in preparation.

Galaxy Clusters as a Probe of SIDM?

Less than cuspy cluster cores? Newman,Treu, Ellis, & Sand

Cosmological Sim of a Galaxy Cluster: 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.

Cosmological Sim of a Galaxy Cluster: 10 15 Msun CDM SIDM σ/m=0.1 cm 2 /g ρcore ~ 3.10 6 M sun /kpc 3 SIDM σ/m=0.5cm 2 /g SIDM σ/m=1cm 2 /g Rocha et al., in prep.

SIDM σ/m=0.5cm 2 /g ρcore ~ 3.10 6 M sun /kpc 3 Newman,Treu, Ellis, & Sand

What Do Baryons Do??

SIDM vs. CDM (no baryonic component) 10 0 10 1 Final CDM halo (10 Gyr) Initial CDM halo 0 Gyr 0.0 Gyrs Baryon10.0 Potential Gyrs 10 Gyr CDM Density [M /pc 3 ] 10 2 10 3 Initial CDM halo Run with SIDM for 10 Gyr Galaxy (grown slowly) 10 4 Elbert et al., in preparation 10 3 10 4 Radius [pc]

SIDM vs. CDM (no baryonic component) Density [M /pc 3 ] 10 0 10 1 10 2 10 3 CDM SIDM 0.0 Gyrs 10.0 Gyrs Initial CDM halo Velocity Dispersion [km/s] 200 180 160 140 120 100 80 SIDM CDM 0.0 Gyrs 10.0 Gyrs 60 10 4 10 3 10 4 Radius [pc] 10 0 10 1 Radius [kpc] Elbert et al., in preparation

e.g. Blumenthal et al. 1986 Simulating Baryonic Contraction 10 0 10 1 Galaxy (grown slowly) Final CDM halo 0 Gyr Baryon Potential 10 Gyr CDM Density [M /pc 3 ] 10 2 10 3 Initial CDM halo 10 4 Elbert et al., in preparation 10 3 10 4 Radius [pc]

Baryons + SIDM 10 0 10 1 Galaxy (grown slowly) Final SIDM halo Final CDM halo halo 0 Gyr 0 Gyr Baryon 10 Gyr Potential CDM 10 Gyr 10 Gyr CDMSIDM Density [M /pc 3 ] 10 2 10 3 Initial halo Initial CDM halo 10 4 Elbert et al., in preparation 10 3 10 4 Radius [pc]

Baryons + SIDM 10 0 10 1 Galaxy (grown slowly)!! Final SIDM halo Final CDM halo halo 0 Gyr 0 Gyr Baryon 10 Gyr Potential CDM 10 Gyr 10 Gyr CDMSIDM Density [M /pc 3 ] 10 2 10 3 Initial halo Initial CDM halo 10 4 Elbert et al., in preparation 10 3 10 4 Radius [pc]

Baryons make SIDM predictions complicated Density [M /pc 3 Density [M /pc 3 ] 10 10 0 0 10 10 1 1 10 10 2 2 10 10 3 3 Galaxy (grown slowly) 0 Gyr 0 Gyr 0 Gyr SIDM + contraction 10 Gyr CDM Baryon 10 Gyr Potential CDM Final SIDM halo 10 Gyr SIDM 10 Gyr 10 Gyr CDMSIDM CDM + contraction Final CDM halo halo 10 Gyr SIDM, no potential Initial Initial halo Initial CDM halo SIDM (No galaxy) 10 10 4 4 Elbert et al., in preparation 10 10 3 3 10 10 4 4 Radius [pc]

SIDM + Baryons = Hard (~CDM + Baryons) 250 SIDM + contraction Velocity Dispersion [km/s] 200 150 100 50 CDM + contraction SIDM (No galaxy) Initial 10 0 10 1 Radius [kpc] 0 Gyr 10 Gyr CDM 10 Gyr SIDM 10 Gyr SIDM, no potential Elbert et al., in preparation

SIDM + Baryons = Hard (~CDM + Baryons) Size of SDM core will relate to baryonic distribution 250 SIDM + contraction Velocity Dispersion [km/s] 200 150 100 50 CDM + contraction SIDM (No galaxy) Initial 10 0 10 1 Radius [kpc] 0 Gyr 10 Gyr CDM 10 Gyr SIDM 10 Gyr SIDM, no potential Elbert et al., in preparation

Smallest Dwarfs: Great DM Laboratories M? 10 6 M r? 500pc M DM M? 50 Dark Matter Dominated => Easy to interpret Very Few Stars => SN Can t Alter DM

The Local Volume is the Next Frontier Observation Theory Masses of LG dwarfs Evan Kirby et al., in prep Simulating Local Groups... Garrison-Kimmel et al., in prep

ELVIS [Exploring the Local Volume In Simulations] Garrison-Kimmel, Boylan-Kolchin, JSB

1. The Too Big to Fail Problem Take-Aways Satellites of MW have lower dark matter densities than expected. - Where are the most massive/dense subhalos? 2. Possible solutions - SN Feedback? Not enough stars to do it. - Any Baryonic process? Could be environmental - test w/ obs of isolated dwarfs - Dark Matter physics? - SIDM with σ/m ~ 0.5-1 cm 2 /g can do it. 3. Where to look for DM weirdness? Baryon-dominated systems are interesting in SIDM but HARD Dark matter dominated dsph s in the Local Field may be the best bet.

The Local Volume Looks Problematic too ELVIS Garrison-Kimmel et al. 2013b Expect ~30-100 dense galaxies with Vmax>30 km/s!

Massive Galaxy Cluster: 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 SIDM: substructure affected at factor of ~2 level max Rocha et al., in prep. Subhalo mass (M sun )

Dark Matter Phenomenology: Substructure CDM SIDM (dashed) # of MW satellites > 20 WDM m s = 6 KeV Horiushi et al. WDM: - Solves Too Big To Fail by removing offending subhalos all together. Problem: - For models that solve the TBTF: not enough subhalos to explain known satellite count - Same models also struggle to explain Ly-alpha forest clumping CDM SIDM WDM

Expect: 0.01 Supernova per solar mass of stars. Req. more energy than sum of all supernovae in this galaxy! Slightly more energy input unbinds the halo all together (fine-tuning problem) # of SN worth of energy Garrison-Kimmel et al. 2013a Energy Required