Gas Accretion & Non-Equilibrium Phenomena in the Outskirts of Galaxy Clusters

Transcription

1 Gas Accretion & Non-Equilibrium Phenomena in the Outskirts of Galaxy Clusters 2.4Msec Chandra XVP observation of A133 Accelerated Expansion R200 Core of the Perseus Cluster Gravity R500 Daisuke Nagai Yale University SnowCluster workshop - March 18, 2015 In collaboration with C. Avestruz, E. Lau, K. Nelson (Yale), A. Vikhlinin (Harvard CfA), A. Kravtsov (U.Chicago), I. Zhuravleva (Stanford), E. Churazov, E. Komatsu, X. Shi (MPA), S. Borgani, E. Rasia (Trieste)

2 Era of Precision Cluster Cosmology X-ray Cluster Cosmology Vikhlinin et al (also Allen+08, Mantz+10) - A. Mantz s talk Local (z<0.1) sample of 49 clusters + 37 high-z clusters from the 400d X-ray selected cluster sample Planck Cosmological Constraints from CMB vs. Cluster counts Planck 2015 N. Aghanim s talk Ω DE KEY: Robust Mass Proxy Yx (excluding cluster cores) σ 8 =0.813(Ω M /0.25) ±0.013(stat)±0.024(sys) w 0 =-0.991±0.045(stat)±0.039(sys) Ω DE =0.740±0.012 Possible Solutions: Cluster mass calibration is biased by 45% Planck CMB results may be biased Sum of the neutrino masses is ~0.2eV Combination of the above Systematics, Systematics, Systematics (1) Mass Calibration & (2) Selection Function Problem: Cluster Astrophysics

3 Weighing the Giants Chandra a few 100 ksec Rsp R200m R200c R500c Suzaku Ultra-deep Chandra >2Msec Planck SZ Unlike stars, galaxy clusters don t have a well-defined edge. So, we need to define the enclosed mass (M ) within a sphere of radius R, within which the average density is times the critical or mean reference background mass density of the Universe. M D 4 3 pr3 D (Dr crit) ref In this talk, I will consider four radii: =500c, 200c, 200m, splash back. R500c: R200c: R200m: Rsp = 1: 1.4: 3: 4 Working Definition of Cluster Outskirts: r>r500

4 X-ray+SZ measurements of cluster outskirts 30: :00: :00.0 SUZAKU X-ray Key Project r200 bkg. cluster Perseus Urban et al E N Planck Coma Planck Collaboration 42:00: :00.0 W IC :00: : :00: :30: kpc 30 arcmin 655 kpc 30: :00.0 3:20: : : kpc Recent X-ray and microwave observations have detected the hot gas in outskirts of galaxy clusters

5 Suzaku+Planck measurements of cluster outskirts Entropy profiles of 11 nearby relaxed clusters Walker et al Gas density from Suzaku Pressure from Planck Gas fraction profile in Perseus cluster? Cosmic Baryon Fraction Expected Gas Fraction K/K(0.3r200)? f gas = M gas M tot Theoretical Expectation K P/n 5/3 =T/n 2/3 r 1.1 Simionescu et al from Suzaku s = logk specific entropy P = Kr 5/3 for monoatomic gas PUZZLES: Observed entropy and gas fraction profiles are strongly inconsistent with theoretical expectations

6 Theoretical Prediction of the ICM Entropy Profile Santa Barbara Cluster Comparison Project (Frenk et al. 1999) Non-radiative simulations with M200c=10 15 Msun and Tx=5keV ROBUST 8Mpc UNCERTAIN r200c (=2.7Mpc) ROBUST PREDICTION: Gas entropy profile increases monotonically at large radii. also Voit et al. 2003

7 Omega 500 Simulation Project High-Resolution N-body+Gasdynamics Cosmological Simulation with Adaptive Refinement Tree (ART) code on Yale s OMEGA HPC Cluster Box size = 500h -1 Mpc, DM particle mass 10 9 h -1 M, Peak Spatial Resolution 3.8 h -1 kpc Kaylea Nelson Erwin Lau Camille Avestruz 500h -1 Mpc zoom-in cosmological hydrodynamical simulations of 65 galaxy clusters with M 500 > 3x10 14 h -1 M in WMAP5 cosmology (Nelson et al. 2014, ApJ, 782, 107) Focus on non-radiative run with electron-proton equilibration process with the Spitzer rate Full Omega500 runs with radiative cooling and star formation (with or without AGN) are underway Check baryonic effects with 16 clusters with cooling and star formation (Nagai et al. 2007)

8 Universal Entropy Profile? Omega 500 Cluster Simulation Project Mean Entropy Profiles of 65 simulated clusters at z=0 and their progenitors 10 z =0.0 z =0.5 z =1.0 z = z =0.0 z =0.5 z =1.0 z =1.5 S/S200c 1 S/S200m 1 Lau, Nagai, Avestruz, Nelson, Vikhlinin, submitted to ApJ (astro-ph/1411,5361) Rsp accretion shock r200c r/r 200c r/r 200m Gas entropy profile is more universal when halos are defined with respect to the mean density than the critical density. Alignment of accretion shocks at R shock R sp = 1.4R 200m

9 Mass Accretion breaks Universality S/S200m 10 1 z =0 0.0 apple 200m apple apple 200m apple apple 200m apple apple 200m r/r 200m Faster accretion Mass Accretion Rate between z=0 and 0.5 (Diemer & Kravtsov 2014) Accretion rate changes location of accretion shock Accretion shock penetrates deeper for faster accreting clusters because of their higher momentum flux

10 How well does gas trace DM? Gas-to-DM density ratio Radial Gas Velocity Dashed: DM Solid: Gas Infall Region outflow inflow Gas inflow is slower than that of DM Gas density does NOT trace DM density perfectly Gas lags behind DM near the location of accretion shocks

11 Missing Cluster Astrophysics #1 Cluster outskirts are very clumpy Mock Chandra X-ray simulation of a ΛCDM cluster (from N07 CSF run) clumps filaments R500 Nagai & Lau 2011 Observed profile affected by gas clumping True profile Avestruz, Lau, Nagai, Vikhlinin, 2014, ApJ, 791, 117 Hydrodynamical simulations predict that most of the X-ray emissions from cluster outskirts (r>r500=0.7r200) arise from infalling groups from the filaments

12 SZ+X-ray Observations of Pressure Profiles in Cluster Outskirts ROSAT: 31 galax clusters at z= Eckert+12 Suzaku: PKS Walker+12 ROSAT data Corrected for clumping Not corrected for clumping Corrected for clumping X-ray r<r500 Arnaud+10 (XMM) Hydro r>r500 Borgani+04 (SPH) Nagai+07 (AMR) Piffaretti+09 (SPH) Lapi+12 (analytical) SZ and X-ray observations provide complementary views of cluster outskirts; i.e., SZ signal is less sensitive to gas clumping, but affected by non-thermal pressure, while both SZ and X-ray signals are susceptible to non-thermal pressure and non-equilibrium electrons. also Eckert+13a,b ; Khedekhar+13

13 Gas Clumpiness vs. Inhomogeneities All Gas Only Bulk Radial Profile with high density tail Radial Profile without high density tail Spatial Distribution of high-density tails Gas inhomogeneities consist of (1) bulk component + (2) high density tail. Power spectrum analysis is a method of choice for characterizing the properties of the bulk component! Zhuravleva et al. 2013; also Roncarelli+13, Vazza+13

14 Gas Clumping Factors Dashed: bulk+high density tail Solid: only bulk Gas clumping R200c=1.5R500c (1) All gas (bulk+high density tail) CX = 3-4 (NR Relaxed) CX = 2.5 (NR Unrelaxed) CX = 1.6 (CSF Relaxed) CX = 2.0 (CSF Unrelaxed) (2) Only bulk component Nagai & Lau (2011) CX = 1.5 (NR Relaxed) CX = 1.8 (NR Unrelaxed) CX = 1.4 (CSF Relaxed) CX = 1.3 (CSF Unrelaxed) Gas clumping factors depend on (1) input gas physics (CSF<NR) (2) details of clump excision (3) dynamical state (but only weakly) Zhuravleva et al. 2013

15 Temperature Inhomogeneities SPH vs. AMR simulations Dispersions in logarithmic gas density and temperature after excluding high- density gas inhomogeneities σ ρ Rasia et al σ T NR SPH NR AMR CSF AMR CSF SPH AGN SPH SPH runs are clumpier than AMR runs, especially in temperature. This introduces differences in the predicted HSE mass bias: 30% (SPH: Rasia+12) & 10-15% (AMR: Nagai+07)

16 Missing Cluster Astrophysics #2 Merger-Induced Gas Motions in Clusters Minor Merger v~300 km/s (subsonic flow) Major Merger V~1000 km/s (transonic flow) R500 Velocity field overlaid on the temperature map Nelson+14a Hydrodynamical simulations predict significant gas motions in clusters. Main source of bias for hydrostatic cluster mass estimate and SZ power spectrum modeling. Observationally, we know very little about gas motions in clusters. Dolag+05, Rasia+06, Nagai+07, Lau+09, Suto+13, Lau+13, Shi+14, Nelson+12

17 Non-thermal Pressure Fraction Profiles Lines = mean Shades = scatter Redshift evolution! 1σ scatter At R500c 18% at z=0 30% at z=1.5 apple P rand (r)=1-a 1 + exp - P total r/r200m ere the best A=0.452 fit parameters B=0.841 areγ=1.628 A =0452 ± B Non-thermal pressure fraction is more universal when halos are defined with respect to the mean density than the critical density. Nelson, Lau, Nagai, 2014 see a poster by Kaylea Nelson

18 Effects of Accretion Rate on Non-thermal Pressure Profiles More non-thermal pressure in strongly accreting clusters P rand P total P total (r;z = 0) =1- ( m ) apple 1 + exp - r/r200m keeping B=0.841, γ=1.628 fixed B Mass accretion rate is the primary source of scatter in the profile Nelson, Lau, Nagai, 2014 see a poster by Kaylea Nelson

19 Analytical Model of Non-thermal Pressure Profiles Shi & Komatsu 2014 (analytical model) Comparison to the Omega 500 simulation d 2 nth dt = 2 nth t d + d 2 tot dt Time Change in Turbulence Energy per unit mass Dissipation of Turbulence Generation of Turbulence sourced by mass accretion Shi, Komatsu, Nelson, Nagai, 2015 Analytical model can match the results of hydrodynamical simulations remarkably well see a poster by Xun Shi

20 Planck SZ power spectrum constrains Cluster Astrophysics Thermal SZ power spectrum contains significant contributions from outskirts of low mass (M<3x10 14 Msun), high-z (z>1) groups at l<5000 Dl [µk 2 ] Dl [µk 2 ] Energy injection from, f DM Stars and SMBHs Shaw, Nagai, Battacharya, Lau 2010 Gas Motions in Clusters l 0 Dark Matter Structures Red: fiducial model: εf =10-6, α0=0.18, β=0.5, nnt=0.8 Calibrated with hydro. sim. A c Evolution of Gas Motions α(z)=α0(1+z) β l l(l +1)Cl/2π Best-fit tsz spectrum Shaw et al. (2010) Battaglia et al. (2013) TBO2 Planck 2015 J. F. Maciras-Perez s talk Multipole l The SZ power spectrum model (with non-thermal pressure) is consistent with the Planck measurement

21 Missing Cluster Astrophysics #3 Electron-Proton Equilibration in Cluster Outskirts CL101 Tx=8keV, unrelaxed In the outskirts of galaxy clusters, the collision rate of electrons and protons becomes longer than the age of the universe. Rudd & Nagai 2009 CL104 CL6 Tx=8keV, relaxed Tx=2keV, unrelaxed Te/Tgas Data: Tspec Line: Tmg 5% at R500c Assumed Spitzer value Upper Limit! 30% at R200m Tgas Te/Tgas Avestruz, Nagai, Lau, Nelson, submitted to ApJ (astro-ph/ ) Spitzer 1962, Takizawa 1999, Chuzhoy & Loeb 2004, Rudd & Nagai 2009, Akahori & Yoshikawa 2010

22 Predictions: Hydrodynamical Simulations of Galaxy Cluster Outskirts Mock Chandra X-ray simulation of a ΛCDM cluster filaments R500 Avestruz, Lau, Nagai, Vikhlinin, 2014, ApJ, 791, 117 clumps (1) ICM inhomogeneities in both gas density and temperature the former important at r>r500c the latter important even in r<r2500c (2) Gas motions - become increasingly important at large radii (r>>r2500c) (3) Non-equilibrium electron - could be important at r>r200c of high-tx, unrelaxed clusters, but the exact prediction depends on still uncertain plasma physics (4) Observational bias (metallicity & multiphase temperature structure) - is a concern at r>r500c (Avestruz+14)

23 Evidence for Gas Clumping & Filaments in Cluster Outskirts 2.4Msec Chandra XVP observation of A133 Vikhlinin et al. in prep. R200 R200 C Flat-fielded, background-subtracted, map 79 clumps detected A 3 Filaments B A transition of the smooth state in the virialized region to a clumpy intergalactic medium in the infall region outside of r R500c

24 Evidence for Gas Clumping & Filaments in Cluster Outskirts R500c R200c CXB included clumps included filaments included If clumps and filaments included, 5 bias in Sx 2 3 in ρgas at R200c 0.85 in T 0.45 in entropy A transition of the smooth state in the virialized region to a clumpy intergalactic medium in the infall region outside of r R500

25 The Edge of the X-ray Cluster? r500c X-ray brightness ρgas ~ r 2.7±0.2 ρgas ~ r 2 edge ρgas ~ r 5.9±1.6

26 The Edge of the X-ray Cluster? Actively accreting cluster? 0 faster accretion ure 7. Dependence of the slope profiles on the mass accretion rate an Diemer & Kravtsov 2014 dark matter (Talks by B. Diemer & A. Kravtsov) gas = d log gas/d log r X-ray brightness faster accretion r/r 200m Lau, Nagai et al. (astro-ph/ ) gas ρgas ~ r 2.7±0.2 ρgas ~ r 2 r500c edge ρgas ~ r 5.9±1.6

27 Contribution of Filaments to Pressure at Large Radius r500c mean Planck profile bulk+filaments Pressure profile in the cluster bulk filaments Gas in the filaments contributes > 50% of total pressure at R200c

28 Galaxy Clusters Outskirts: New Frontier and Crossroads of Cosmology & Astrophysics Use R500m for Outskirts Work R200 R500c C Cluster Core (r<0.2r 500c ) Heating, Cooling, & Plasma physics 1. AGN feedback (Mechanical/CR heating) 2. Dynamical Heating, Gas sloshing 3. Thermal Conduction, Magnetic Field, He sedimentation Core Cluster outskirts (r>r 500c ) Gas Accretion & Non-equilibrium phenomena 1. Gas clumping/inhomogeneities 2. Gas motions 3. Non-equilibrium electrons A B Intermediate Region (r~r 500c ) Sweat Spot for Cluster Cosmology, but the physics of cluster outskirts affects this region.