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Various Mostly Lagrangian Things

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kiele
28 diapositives · 447 Views · Sep 22, 2014

This study presents a detailed analysis of the cosmic web through Lagrangian frameworks. We emphasize comparisons in Lagrangian space, investigate halo spins in an origami model, and explore Lagrangian substructures. By incorporating rotation into velocity-field classifications, we reveal insights into halo bias in voids. Our approach utilizes powerful N-body simulations in phase space, drawing analogies to origami, and discusses implications of the flat-origami approximation on galaxy spins and structural formations. Various collaborators contribute to elucidating these themes.

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Various Mostly Lagrangian Things
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  1. Various Mostly Lagrangian Things Mark Neyrinck Johns Hopkins University Collaborators: Bridget Falck, Miguel Aragón-Calvo, Xin Wang, Donghui Jeong, Alex Szalay Tracing the Cosmic Web, Leiden, Feb 2014

  2. Outline • Comparison in Lagrangian space • Halo spins in an origami model • Lagrangian substructures • Incorporating rotation into a velocity-field classification • Halo bias deeply into voids with the MIP • Mark Neyrinck, JHU

  3. Information, printed on the spatial “sheet,” tells it where to fold and form structures. 200 Mpc/h • Mark Neyrinck, JHU

  4. (e.g. analytical result in Bertschinger 1985) Why “folding?” In phase space ... • Mark Neyrinck, JHU

  5. N-body cosmological simulation in phase space: a 2D slice vx x y z x y • Mark Neyrinck, JHU

  6. Rough analogy to origami: initially flat (vanishing bulk velocity) 3D sheet folds in 6D phase space. - The powerful Lagrangian picture of structure formation: follow mass elements. Particles are vertices on a moving mesh. - Eulerian morphologies classified by Arnol’d, Shandarin & Zel’dovich (1982) - See also Shandarin et al (2012), Abel et al. (2012) … Eric Gjerde, origamitessellations.com

  7. The Universe’s crease pattern Crease pattern before folding After folding • (Neyrinck 2012; Falck, Neyrinck & Szalay 2012)

  8. Web comparison in Lagrangian coordinates Warming up: Lagrangian → Eulerian → Lagrangian for ORIGAMI • Mark Neyrinck, JHU

  9. Web comparison in Lagrangian coordinates ORIGAMI • Mark Neyrinck, JHU

  10. Web comparison in Lagrangian coordinates Forero & Romero • Mark Neyrinck, JHU

  11. Web comparison in Lagrangian coordinates Nuza, Khalatyan & Kitaura • Mark Neyrinck, JHU

  12. Web comparison in Lagrangian coordinates NEXUS+ • Mark Neyrinck, JHU

  13. Flat-origami approximation implications: • Assumptions: no stretching, minimal #folds to form structures - # of filaments per halo in 2D: generically 3, unless very special initial conditions are present. - # of filaments per halo in 3D: generically 4. Unless halo formation generally happens in a wall

  14. Flat-origami approximation implications: • Galaxy spins? • To minimize # streams, haloes connected by filaments have alternating spins • Are streams minimized in Nature? Probably not, but interesting to test. • A void surrounded by haloes will therefore have an even # haloes — before mergers

  15. Chirality correlations Connect to TTT (tidal torque theory): haloes spun up by misaligned tidal tensor, inertia tensor. Expect local correlations between tidal field, but what about the inertia tensor of a collapsing object? - Observational evidence for chiral correlations at small separation (… Pen, Lee & Seljak 2000, Slosar et al. 2009, Jiminez et al. 2010)

  16. ORIGAMI halo spins in a 2D simulation • Galaxy spins? • To minimize # streams, haloes connected by filaments have alternating spins • A void surrounded by haloes will therefore have an even # haloes

  17. Lagrangian slice: initial densities • Mark Neyrinck, JHU

  18. Lagrangian slice: VTFE* log-densities *Voronoi Tesselation Field Estimator (Schaap & van de Weygaert 2000) • Mark Neyrinck, JHU

  19. Lagrangian slice: LTFE* log-densities Halo cores fairly good-looking! *Lagrangian Tesselation Field Estimator (Abel, Hahn & Kahler 2012, Shandarin, Habib & Heitmann 2012) • Mark Neyrinck, JHU

  20. Lagrangian slice: ORIGAMI morphology node filament sheet void • Mark Neyrinck, JHU

  21. LTFE in Lagrangian Space — evolution with time

  22. “Time spent as a filament/structure” map • Mark Neyrinck, JHU

  23. Morphologies with rotational invariants of velocity gradient tensor Slides from Xin Wang

  24. both potential & rotational flow SN-SN-SN (halo) UN-UN-UN (void) SN-S-S (filament) UN-S-S (wall) SFS UFS SFC UFC Slides from Xin Wang 1Mpc/h Gaussian filter, using CMPC 512 data

  25. Slides from Xin Wang Stacked rotational flow from MIP simulation

  26. Halo bias deeply into voids without stochasticity/discreteness with Miguel’s MIP simulations MN, Aragon-Calvo, Jeong & Wang 2013, arXiv:1309.6641 • Mark Neyrinck, JHU

  27. Not much environmental dependence beyond the density by eye! Comparison of:Halo-density field withHalo-density field predicted from the matter field • Mark Neyrinck, JHU

  28. “Conclusion” Visualization of the displacement field • Mark Neyrinck, JHU