Simulating Galaxy Cluster Mergers by Daisuke Nagai

A talk on "Simulating Galaxy Cluster Mergers" by Daisuke Nagai at the Feeding, Feedback, Fireworks conference, Hamilton Island, Australia in June, 2013.

Transcript

1. Daisuke Nagai Computational Cosmology Group @ Yale University Feeding, Feedback & Fireworks Hamilton Island 2013 Simulating Galaxy Cluster Mergers Feeding & Fireworks on Large Scales Core of the Perseus Cluster Fabian et al. 2003
2. Chandra Cluster Cosmology Project Vikhlinin et al. 2009 σ 8 =0.813(Ω M /0.25)-0.47±0.013(stat)±0.024(sys) w 0 =-0.991±0.045(stat)±0.039(sys) Ω DE =0.740±0.012 Local (z<0.1) sample of 49 clusters + 37 high-z clusters from the 400d X-ray selected cluster sample Era of Precision Cluster Cosmology Systematics, Systematics, Systematics.. Ω DE
3. Recent Advances in Cluster Cosmology Before Dark Energy Task Force (2006) Now Uncertain by 100% Accurate to 10% ASCA X-ray observations Finoguenov et al. 2001 Hydro. sim. without “galaxies” Evrard et al. 1996 Hydro. sim. with “galaxies” Kravtsov et al. 2006 Nagai et al. 2007 Chandra X-ray obs. Vikhlinin et al. 2006 excluding cluster cores (r<0.15r500)
4. Cluster Cosmology in 2010s All-sky survey for 4yrs + targeted obs. Science Goals: Study the LSS and Dark Energy >100,000 clusters up to z~1.5 A eff ~1500 cm2 @ 1.5keV; Θ eff ~25-40 arcsec eROSITA (launch in 2015) Outstanding Challenges: Need to measure cluster mass to a few %!! Sunyaev-Zeldovich (SZ) Effect SZE is independent of redshift with a robust mass proxy X-ray X-ray X-ray Several hundred clusters have been discovered by ACT, SPT, and Planck recently SPT ACT Planck
5. Modern cosmological hydro simulations include the effects of baryons (i.e., gas cooling, star formation, heating by SNe/AGN, metal enrichment and transport). But, also remember limitations - e.g., a single fluid approximation! N-body+Gasdynamics with Adaptive Refinement Tree (ART) code Box size ~ 80/h Mpc; Region shown ~ 2/h Mpc; Spatial resolution ~ a few kpc Cosmological Simulations of Galaxy Cluster Formation
6. Radial profiles of X-ray emitting ICM Simulations vs. Chandra X-ray Observations Temperature Gas density Modern hydrodynamical cluster simulations reproduce observed ICM profiles outside cluster cores (0.15<r/r500 <1). Nagai, Kravtsov & Vikhlinin 2007, ApJ, 668, 1 Core physics still remains uncertain Radiative cooling, AGN feedback, thermal conduction, CRs, magnetic field Cluster outskirts are modeled remarkably well
7. PKS 0745-191 3500 kpc George et al. 2009 Cluster Core SUZAKU X-ray Obs. X-ray+SZ measurements of cluster outskirts Planck Coma Planck Collaboration 6000 kpc
8. K≡T/n2/3∝r1.1 Walker et al. 2012 Gas density from Suzaku Pressure from Planck PUZZLES: Observed entropy and gas fraction profiles are strongly inconsistent with theoretical expectations Entropy profiles of 11 nearby relaxed clusters Simionescu et al. 2011 from Suzaku Suzaku+Planck measurements of cluster outskirts Gas fraction profile in Perseus Cosmic Baryon Fraction Expected Gas Fraction Theoretical Expectation ? ?
9. D. Nagai & E. Lau 2011, ApJ, 731, L10 Mock Chandra X-ray simulation of a ΛCDM cluster R500 Median spherically-averaged clumping profile of hot X-ray emitting gas for the sample of 16 simulated clusters Missing Cluster Astrophysics #1 Cluster outskirts are very clumpy Hydrodynamical cluster simulations also predict that most of the X-ray emissions from cluster outskirts (r>r500) arise from small groups accreting along filaments
10. Mock Chandra X-ray simulation of a ΛCDM cluster R500 Gas Clumping introduce biased in the ICM profiles derived from X-ray observations Hydrodynamical cluster simulations predict that most of the X-ray emissions from cluster outskirts (r>r500) arise from infalling groups from the filaments Observed profile affected by gas clumping True profile D. Nagai & E. Lau 2011, ApJ, 731, L10
11. Evidence for Gas Clumping in Cluster Outskirts R200 R500 A transition of the smooth state in the virialized region to a clumpy intergalactic medium in the infall region outside of r ≈ R500 Vikhlinin et al. in prep. 2.4Msec Chandra XVP observation of A133 Flat-fielded, background-subtracted, point-source subtracted map
12. Evidence for Gas Clumping in Cluster Outskirts Chandra observations of A133 Flat-fielded, background-subtracted image, point sources removed A transition of the smooth state in the virialized region to a clumpy intergalactic medium in the infall region outside of r ≈ R500 Vikhlinin et al. in prep. 2.4Msec Chandra XVP observation of A133 79 wavelet-detected X-ray clumps overlaid
13. Gas (bulk+turbulent) motions are predicted to be ubiquitous in ICM Drivers of gas motions Accretion/Mergers (on large scales) Energy injection from SNe/AGN (in cluster cores) Plasma instabilities Broad Implications Hydrostatic mass modeling ICM profiles X-ray/SZ observable-mass relations SZ power & bispectra Metal distribution (e.g., by mixing) Particle acceleration 2h-1 Mpc Missing Cluster Astrophysics #2 Merger-Induced Gas Motions in Clusters Major Merger M~1-3 (transonic) Minor Merger M~0.3 (subsonic) 0.82h-1 Mpc Observationally, we know very little about the nature of gas motions in clusters!!
14. Non-thermal pressure due to gas motions introduces bias in the hydrostatic mass estimate at a level of 5-35% at R500. The mass bias is larger for disturbed clusters. Also Dolag+05, Rasia+06, Vazza+09, Battaglia+11, Nelson+12 Gas motions is one of the dominant sources of systematic bias in SZ/X-ray cluster mass estimates Hydrodynamical simulations predict the ratio of kinetic energy in turbulent gas motions to thermal energy content of galaxy clusters in ΛCDM models 0.2 0 -0.2 -0.4 1014 1015 Lau, Kravtsov, Nagai 2009 Nagai, Vikhlinin, & Kravtsov 2007 unrelaxed relaxed Bias in HSE mass: MHSE/Mtrue
15. Planck 2013, Papers XVI, XX Cosmology in the Planck Era Clusters vs. CMB cluster scaling relations are off by ~45% Planck CMB results may be biased sum of the neutrino masses is ~0.2-0.25eV a combination of bias in cluster scaling relations, Planck CMB constraints, and non-zero neutrino masses Possible Solutions Planck cosmological constraints from CMB are in tension with cluster abundances
16. 0 5×105 106 1.5×106 Black: Clump1+Clump2 (composite) Red: Clump1 v=219 km/s Green: Clump2 v=361 km/s 6.2 6.4 6.6 6.8 −5×104 0 5×104 Energy (keV) Best-fit Clump1: TX=8.5keV vshift=+152km/s σ=219km/s Clump1+Clump2 (composite) Best-fit Clump2: TX=11keV vshift=-342km/s σ=361km/s 0.3r500 Clump 2 Clump 1 Merging Cluster with Tx=10keV R500 zobs=0.068 Probing Gas Motions in Merging Galaxy Clusters with Astro-H X-ray mission Astro-H (2015) Astro-H will measure peculiar velocity and turbulent gas flows in massive galaxy clusters via shifting and broadening of Fe line. Nagai et al., in prep. to appear in astro-ph next week Mock Astro-H photon maps in 6-7keV
17. High-Resolution SZ studies of Individual Clusters with CCAT High-resolution, multifrequency SZE observations are unique probes of thermodynamic and velocity structures of the ICM. measurements! es! ? r! de! ! 2013!F!CCAT!Session! 5! Credit:!Mike!Zemcov! Credit: Mike Zemkov CCAT (2018) Thermodynamic structure of the ICM Temperature profile via SZ relativistic corrections (independently from X-ray) Inhomogeneities in the ICM (gas clumping) Non-thermal pressure in clusters Bulk vs. Turbulent motions via kSZ substructure tSZ effect @ 93GHz kSZ effect @ 221GHz Mock CCAT simulations Morandi, Nagai, Cui, 2013, MNRAS, 431, 1240 Angular resolution 12’’@1mm
18. Electron temperature is lower than gas (or ion) temperature in the outskirt of dynamically active clusters Rudd & Nagai, 2009 Spitzer 1962, Chuzhoy & Loeb 2004, Akahori & Yoshikawa 2010 Tx=2keV, relaxed Tx=8keV, relaxed Tx=8keV, unrelaxed 4 6 8 0.2 0.6 1.0 CL101 CL104 CL6 Tx=8keV, relaxed Tx=2keV, unrelaxed Tx=8keV, unrelaxed Tgas Te/Tgas Missing Cluster Astrophysics #3 Non-equilibrium Electrons in Merging Clusters
19. Cluster outskirt is a new territory for studying feeding & fireworks of galaxy cluster mergers Important for understanding thermodynamic and chemical evolution of clusters ★ Cluster outskirts are turbulent and clumpy filled with non-equilibrium electrons Critical for cluster-based cosmological tests ★ Calibration of observable-mass relations ★ Cosmological inference from multi-wavelength cluster surveys Feeding & Fireworks in Galaxy Cluster Mergers Astro-H (2015) eROSITA (2015) SPT ACT Planck ALMA CCAT (2018) Planck Cosmological Constraints from CMB vs. Cluster counts CARMA MUSTANG Hydrodynamical Simulations of Galaxy Clusters R200 R500 Chandra observation of A133