A Comprehensive Assessment of the Too-Big-to-Fail Problem Arthur - PowerPoint PPT Presentation

A Comprehensive Assessment of the Too-Big-to-Fail Problem Arthur Fangzhou Jiang Advisor: Frank van den Bosch Yale University Acknowledgments: Peter Behroozi , Mike Boylan-Kolchin, Shea Garrison-Kimmel, Erik Tollerud, Andrew Hearin, Duncan Cambell Workshop on Cosmological Structures, ICTP, Trieste Friday, May 22, 15 1

Outline What is “Too Big To Fail” (TBTF) ? Semi-analytical model of dark matter subhaloes Severity of TBTF Professional Seminar, Yale University Friday, May 22, 15 2

TBTF LMC: ≈ 80km/s Formulation I: SMC: ≈ 60km/s simulation: order of 10 subhaloes with V max >25 km/s MW dSphs: V max ≤ 25 km/s “massive subhalo” formulation Formulation II: a V max gap between ≈ 60km/s and ≈ 25km/s V circ ( r 1/2 ) Wolf et al. (2010) Boylan-Kolchin et al. (2012) Workshop on Cosmological Structures, ICTP Friday, May 22, 15 3

Formulation III: Boylan-Kolchin et al. (2011) Γ = 0 1 = Γ R max : Γ = 2 the radius at which Vcirc(r) reaches Vmax subhalo density proxy Γ ≡ 1 + log(0 . 0014 V 2 . 2 max /R max ) Purcell & Zentner (2012) the most massive subhaloes are too dense ( ) to be Γ max > 1 consistent with MW dSphs ( ) Γ < 1 Workshop on Cosmological Structures, ICTP Friday, May 22, 15 4

Outline What is “Too Big To Fail” (TBTF) ? Semi-analytical model of dark matter subhaloes Severity of TBTF Workshop on Cosmological Structures, ICTP Friday, May 22, 15 5

Merger Tree (EPS) mass evolution: Jiang & van den Bosch (2014a) ⇣ m ⌘ 0 . 07 m = − A m d N ˙ Parkinson et al. (2008): d m ( m, z | M 0 , z 0 ) d m M τ dyn : log-normal unevolved subhalo mass function P ( A ) reflects variance in orbital properties & halo concentrations abundance disruption: e v m dis = m acc ( < α × r s , acc ) o l v e d : log-normal P ( α ) α = ¯ ¯ α ( m acc /M acc ) stucture evolution: mass V max = V acc × f ( m/m acc ) Penarrubia et al. (2010) V acc = g ( m acc , c acc ) For more about subhalo evolution: Jiang & van den Bosch (2014b) Zhao et al. (2009) arXiv:1403.6827 Workshop on Cosmological Structures, ICTP Friday, May 22, 15 6

Model: Accurate Halo-to-Halo Variance benchmark: Bolshoi simulation 441 M 0 = 10 13 . 5 ± 0 . 05 h � 1 M � 1986 M 0 = 10 12 . 10 ± 0 . 01 h � 1 M � model: 500 M 0 = 10 13 . 5 h � 1 M � 2000 M 0 = 10 12 . 1 h � 1 M � Jiang & van den Bosch, submitted to MNRAS Workshop on Cosmological Structures, ICTP Friday, May 22, 15 7

Outline What is “Too Big To Fail” (TBTF) ? Semi-analytical model of dark matter subhaloes Severity of TBTF Workshop on Cosmological Structures, ICTP Friday, May 22, 15 8

“Massive Subhalo” Count definition: Jiang & van den Bosch, submitted to MNRAS V acc > 30kms − 1 V max > 25kms − 1 MW has 2 MSs Wang et al. (2012): lower MW halo mass ==> significantly lower number of MSs Contemporary MW halo mass constraint: 2 M 0 ∈ [10 11 . 7 , 10 12 . 2 ] h � 1 M � Kafle et al. (2014) 10,000 realizations for each halo mass Workshop on Cosmological Structures, ICTP Friday, May 22, 15 9

V max Gap V max (estimates) for MW satellites from Kuhlen et al. (2010) Boylan-Kolchin et al. (2012) Kallivayalil et al. (2013) for MW satellites with no published V max , use MacConnachie (2012) 10000 realizations V max = 2 . 2 σ LOS , ? M 0 = 10^11.8 Msun/h 55 25 Rashkov et al. (2012) Jiang & van den Bosch, submitted to MNRAS V circ ( r | R max , V max , α ) Einasto shape parameter, typically 0.18 (Aquarius) Workshop on Cosmological Structures, ICTP Friday, May 22, 15 10

MW-consistent fraction as a function of halo mass 10,000 realizations for each halo mass N G ap ≤ 1 Jiang & van den Bosch, submitted to MNRAS (number of subhaloes in the gap ≤ 1) V max ∈ [25 , 55]kms − 1 or V max ∈ [30 , 60]kms − 1 Nu ≥ 2 (number of MC analogs ≥ 2) V max > 55kms − 1 or V max > 60kms − 1 N G ap ≤ 1 & N u ≥ 2 probability of having MW-consistent Vmax Gap: always <1% Workshop on Cosmological Structures, ICTP Friday, May 22, 15 11

Subhalo Density recap: MW-consistent <==> Γ max < 1 also can be alleviated by lowering MW halo mass sensitive to cosmology change WMAP7 ( Ω m , σ 8 ) = (0 . 266 , 0 . 801) Planck ( Ω m , σ 8 ) = (0 . 318 , 0 . 834) cosmology comes in mainly via R max Jiang & van den Bosch, submitted to MNRAS Workshop on Cosmological Structures, ICTP Friday, May 22, 15 12

Summary If TBTF is the missing massive subhaloes: MW-consistent fraction <1% for MW-size haloes (M 0 =12.0) reconcilable by lowering MW halo mass, MW-consistent fraction ≥ 10% for M 0 =11.8 not very sensitive to cosmology (WMAP7 versus Planck) If TBTF is the massive subhaloes being too dense: MW-consistent fraction <5% for MW-size haloes (M 0 =12.0) reconcilable by lowering MW halo mass, MW-consistent fraction ≈ 10% for M 0 =11.8 (WMAP7) very sensitive to cosmology: ≈ 3% for M 0 =11.8 (Planck) If TBTF is a V max Gap: MW-consistent fraction always <1%, irrespective of MW halo mass or cosmology Workshop on Cosmological Structures, ICTP Friday, May 22, 15 13

Why semi-analytical model? Why not simulations ? ELVIS: Jiang & van den Bosch, submitted to MNRAS 48 haloes M 0 = 10 12 . 08 ± 0 . 23 h � 1 M � Model: 4800 realizations of ELVIS-size haloes <==> 100 mock ELVIS suites Workshop on Cosmological Structures, ICTP Friday, May 22, 15 14