Moving mesh cosmology: The hydrodynamics of galaxy formation

Transcription

1 Moving mesh cosmology: The hydrodynamics of galaxy formation arxiv: Debora Sijacki, Hubble Fellow, ITC together with: Mark Vogelsberger, Dusan Keres, Paul Torrey Shy Genel, Dylan Nelson Volker Springel, Lars Hernquist MPIA Conference See also Vogelsberger et al Keres et al Torrey et al Bauer & Springel arxiv: arxiv: arxiv: , MNRAS

2 The Santa Barbara Cluster Comparison Project Frenk et al Non-radiative cosmological hydrodynamical simulations comparison of 12 different codes

3 The Santa Barbara Cluster Comparison Project Frenk et al SPH simulations: power-law entropy profiles GRID-based simulations: cored entropy profiles

4 Discrepancy between SPH and grid entropy profiles What causes this discrepancy? - lower effective resolution of grid codes? - different gravity solvers? - Galilean non-invariance of the truncation error in grid codes? - artificial viscosity of SPH codes? - treatment of fluid instabilities? - gravitational N-body noise? Mitchell et al Springel et al FUNDAMENTAL IMPLICATIONS FOR: - UNDERSTANDING ASTROPHYSICS OF GALAXY CLUSTERS - USING GALAXY CLUSTERS AS HIGHPRECISION COSMOLOGICAL PROBES

5 CODE COMPARISON PROJECT GADGET (Springel et al. 2005) Lagrangian method (SPH) particles act as fluid elements AREPO (Springel et al. 2010) finite volume method on a moving mesh (Lagrangian nature) IDENTICAL INITIAL CONDITIONS IDENTICAL GRAVITY SOLVER IDENTICAL SUB-GRID PHYSICS DIFFERENT HYDRO SOLVER TESTS WITH INCREASING COMPLEXITY from idealized experiments with known analytic solutions to realistic, cosmologically motivated simulations UNDERSTAND DIFFERENCES IN FULL COSMOLOGICAL SIMULATIONS

6 Interacting shock waves Implosion experiment (Hui et al. 1999): 1. shock and contact discontinuities much sharper in AREPO 2. intrinsic noise of multidimensional flows in standard SPH 3. absence of Richtmyer-Meshkov instability PERIODIC BOX IN 2D

7 Interacting shock waves: Vorticity generation GADGET 2002 AREPO

8 Bow shock in 3D time BLOB experiment (Agertz et al. 2007): HOT WINDTUNNEL COLD BLOB

9 Generalized Blob Test - static dark matter halo with Hernquist profile - gas in hydrostatic equilibrium - 10 gaseous blobs in pressure equilibrium R = 20kpc, v = km/s

10 Generalized Blob Test: Where does the blob material end up?

11 Generalized Blob Test DIFFERENT STRIPPING IN AREPO LEADS TO DIFFERENT ORBITS OF THE BLOBS AND MORE MIXING WITH THE ICM AREPO HIGH RES AREPO LOW RES GADGET HIGH RES GADGET LOW RES

12 Inside-out disk formation - static dark matter halo with a Hernquist profile - gas in hydrostatic equilibrium which cools and has a net spin disk forms - 10 realistic gas+stars+dm substructures with v = km/s

13 Inside-out disk formation - SFR in AREPO disks higher - SFR in AREPO substructures lower

14 Cosmological simulations Gas Disk Properties - Projected surface density maps of 5 matched halos from cosmological simulations performed with GADGET and AREPO at z = 0 Torrey, Vogelsberger, Sijacki, Springel, Hernquist, arxiv: and in prep.

15 Stacked surface density profiles - GADGET gas surface density profiles steeper - AREPO gas surface density profiles have larger disk scale lengths Torrey et al.

16 Disk scale lengths - Disk scale lengths ~ 2 times larger in AREPO for a given halo mass WITH CENTRAL REGION Torrey et al. WITHOUT CENTRAL REGION

17 Interaction of the gaseous blobs with the central disk AREPO GADGET ~1Mpc ~80kpc Torrey et al.

18 Interaction of the gaseous blobs with the central disk - Large population of gaseous 'blobs' not present in AREPO - in GADGET total mass in the blobs comparable to the central disk mass Torrey et al.

19 Interaction of the gaseous blobs with the central disk GADGET Nngb = 16 Nngb = 32 - Blob mass spectrum AREPO Torrey et al.

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