dynamics & multiscale morphology cosmic web
DESCRIPTION
Dynamics & Multiscale Morphology Cosmic Web. Rien van de Weygaert 3 rd KIAS Workshop, Oct 27-28, Seoul, 2008. Collaboration & References: Pablo Araya- Melo Miguel Aragon- Calvo - PowerPoint PPT PresentationTRANSCRIPT
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Dynamics & Dynamics & Multiscale Multiscale
Morphology Morphology
Cosmic Web Cosmic Web
Rien van de Weygaert
3rd KIAS Workshop, Oct 27-28, Seoul, 2008
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Collaboration & References:Collaboration & References:
Pablo Araya-MeloPablo Araya-Melo
Miguel Aragon-Calvo Miguel Aragon-Calvo
Erwin Platen Erwin Platen
Emilio Romano-Diaz Emilio Romano-Diaz
Willem Schaap Willem Schaap
Bernard Jones Bernard Jones
Gert Vegter (comp. geometry & Gert Vegter (comp. geometry &
topology) topology)
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Foams in Foams in NatureNature
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Foams in Foams in NatureNature
The largest complex pattern found in nature is Megaparsec Scale:
the Cosmic Web
manifestation of the gravitational origin, emergence and growth of ALL structure in the cosmos …
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The Cosmic The Cosmic WebWebStochastic
Spatial
Pattern of
Clusters,
Filaments &
Walls
around
Voids
in which matter,
(DM, gas, gal’s)
has agglomerated
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The Cosmic The Cosmic WebWeb
Significance:Significance: Manifestation mildly nonlinear Manifestation mildly nonlinear clustering: clustering:
Transition stage between linear phase Transition stage between linear phase
and fully collapsed/virialized objectsand fully collapsed/virialized objects
Weblike configurations contain Weblike configurations contain
cosmological information: cosmological information: e.g. Void shapes & alignments (recent e.g. Void shapes & alignments (recent study J. Lee 2007)study J. Lee 2007)
Cosmic environment within which to Cosmic environment within which to understand the understand the
formation of galaxies.formation of galaxies.
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Web Web AnalysisAnalysis Translate discrete galaxy/particle distribution into continuous density field/image:
- DTFE: Delaunay Tessellation Field Estimator
(Post)processing:
- filtering/smoothing image
- identifying clusters (peaks in image)
- identifying filaments/walls: * MMF & spine (Morse theory)
- tracing void regions: * watershed transform (Morse theory)
- topological aspects * alpha shapes
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The Cosmic The Cosmic WebWebWeb Discretely Sampled:
By far, most information on the
Cosmic Web concerns
discrete samples:
• observational:
Galaxy Distribution
• theoretical:
N-body simulation particles
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Power ofPower of
Tessellations Tessellations
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Multiscale Multiscale MorphologyMorphologyFilter Filter
MMF dissection of cosmic web
into sheets, filaments, clusters …
filament
cluster
sheet
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Spine of the Cosmic Web:Spine of the Cosmic Web: Morse complex & search for Morse complex & search for singularities singularities
Spine of the Cosmic Web:Spine of the Cosmic Web: Morse complex & search for Morse complex & search for singularities singularities
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Watershed Void Identification Watershed Void Identification
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Alpha Alpha ShapesShapes
Alpha Shape ofcosmological simulation
left to right: alpha value increases.
LSSLSS
TopologyTopology
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Cosmic WebCosmic Web
Evolution &Evolution &DynamicsDynamics
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Dynamical Evolution Cosmic Dynamical Evolution Cosmic Web Web
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● hierarchical structure formation
● anisotropic collapse
● void formation: asymmetry overdense vs.
underdense
Dynamical Evolution Cosmic Dynamical Evolution Cosmic Web Web
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● Gravitational Instability:Gravitational Instability:
- any small initial deviation from sphericity of a collapsing cloud - any small initial deviation from sphericity of a collapsing cloud gets magnified gets magnified
- gravitational collapse proceeds along sequence: - gravitational collapse proceeds along sequence:
● collapse along smallest axis planar geometry wall
● collapse medium axis elongated filament
● full 3-D collapse clump halo
clump/halo virialization cosmic object
Anisotropic Anisotropic CollapseCollapse
(courtesy: A.
Kravtsov).
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Formative agent of the Cosmic Web:Formative agent of the Cosmic Web:
Tidal strain induced my the Megaparsec Matter Distribution: - anisotropic collapse of structures - connection clusters-filaments: clusters main agent for stretching filaments
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Ellipsoidal Ellipsoidal CollapseCollapse
Self-gravity
Internal tidal shear (due to shape)
External tidal shear
spherical
short axis
medium axis
long axis
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Cosmic Web & Cosmic Web & ClustersClusters
Perseus Cluster (A426)
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Tidal Constraints:Tidal Constraints:Example: elongated filamentary feature
Constrained Field:
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Cosmic Web Theory:
Specification Cluster Node Locations & Orientation:
Outline Cosmic Web
Bond & Myers 1996
Bond et al. 1996
Spatial structure of Cosmic Web structure present in primordial density field.
Geometry of primordial field mainly filamentary (not Zel’dovich sheets), by sheer of statistics Gaussian field.
Filaments defined by tidal field imposed by cluster patches.
Incremental improvement of cosmic web spatial outline by inserting more and more clusters
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Cosmic Web Theory :
Specification Cluster Node Locations & Orientation:
Outline Cosmic Web
Bond & Myers 1996
Bond et al. 1996
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Cosmic Web Theory :
Specification Cluster Node Locations & Orientation:
Outline Cosmic Web
Bond et al. 1996
Spatial structure of Cosmic Web structure present in primordial density field.
Geometry of primordial field mainly filamentary (not Zel’dovich sheets), by sheer of statistics Gaussian field.
Filaments defined by tidal field imposed by cluster patches.
Incremental improvement of cosmic web spatial outline by inserting more and more clusters
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Multiscale Nature Anisotropic Collapse
Structure arises over
a vast range of scales
- Small scales:
fully collapsed objects
- Very large scales:
still linear (& Gaussian) - Medium Mpc scales:
weblike features
Two analytical formalisms:
statistical Press-Sch.
dynamical PeakPatch
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Hierarchical Pattern Hierarchical Pattern FormationFormation
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Hierarchical Void Hierarchical Void Evolution:Evolution:
“Local” Excursion Set Approach
Two-barrier description:
- void merger
- void collapse
Peaked Void Size DistributionVoid Void MergingMerging
Void Void CollapseCollapse
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Galaxy/HaloGalaxy/Halo&&
Web Web EnvironmentEnvironment
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Halo Shape Halo Shape AlignmentsAlignmentsHalo & Halo & Galaxy Galaxy
EnvironmenEnvironmentaltal
Influences Influences
Halo ShapeHalo Shape
AlignmentAlignment
evolutionevolution Filaments: Haloes elongated along filamentFilaments: Haloes elongated along filament
Walls: Haloes elongated within plane wall Walls: Haloes elongated within plane wall (major axis in wall)(major axis in wall)
Orientation weakens in timeOrientation weakens in time
Effect stronger for low-mass haloesEffect stronger for low-mass haloes
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Spinning the GalaxiesSpinning the Galaxies
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Spinning the GalaxiesSpinning the Galaxies
Spinning Up
a collapsing protogalaxy
by Tidal Torque
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Spinning the GalaxiesSpinning the Galaxies
Spinning the Galaxies:
Tidal Forces that also Shape Cosmic Web
Connection
Galaxy Spin
Cosmic Web
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Cosmic Cosmic Web:Web:Environmental Environmental ImpactImpactHalo & Galaxy Formation:Halo & Galaxy Formation:
Environmental influences Environmental influences
Environmental Environmental dependence dependence
strongest wrt. strongest wrt. Alignments:Alignments:
- halo shape- halo shape
- halo spin direction- halo spin direction
To be understood from To be understood from the the
crucial role of tidal crucial role of tidal forces in forces in
shaping the Cosmic shaping the Cosmic WebWeb
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Cosmic Cosmic Web:Web:Environmental Environmental ImpactImpactHalo & Galaxy Formation:Halo & Galaxy Formation:
Environmental influences Environmental influences
Halo Spin distribution in Halo Spin distribution in clusters, clusters,
filaments filaments & sheets & sheets
Environmental Environmental dependence on the halo dependence on the halo spin distributionspin distribution
To a large extent To a large extent influenced by presence influenced by presence of unbound particles of unbound particles
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Halo Spin Halo Spin AlignmentsAlignments
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Halo Spin Halo Spin AlignmentsAlignmentsHalo & Halo & Galaxy Galaxy
EnvironmenEnvironmentaltal
Influences Influences
Halo SpinHalo Spin
AlignmentAlignment
evolutionevolution Filaments:Filaments:High-mass haloes: always perpendicularHigh-mass haloes: always perpendicular
Low-mass haloes: starting perpendicular, they Low-mass haloes: starting perpendicular, they evolve to parallelevolve to parallel
Walls:Walls:High & Low-mass: always in plane of wallHigh & Low-mass: always in plane of wall
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Filament-Galaxy alignment SDSS DR5
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Filament-Galaxy alignment SDSS DR5
Jones et al. 2008 (in prep.) edge-on galaxies
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Cosmic WebCosmic Web
AnalysisAnalysis
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Discrete Point/Galaxy Distribution Continuous FieldDiscrete Point/Galaxy Distribution Continuous Field
(Sibson 1980, 1981; Watson 1992)(Sibson 1980, 1981; Watson 1992)
Natural NeighbourNatural Neighbour
InterpolationInterpolation
Exploiting the Adaptive Nature of Voronoi/Delaunay TessellationsExploiting the Adaptive Nature of Voronoi/Delaunay Tessellations
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Point Sample Point Sample Continuous FieldContinuous Field
Aspects: ● Anisotropy of Aspects: ● Anisotropy of
Structural Features Structural Features
● ● Hierarchical Hierarchical
InfrastructureInfrastructure
● ● Voids, cq. empty Voids, cq. empty
regionsregions
● ● Inhomogeneous Inhomogeneous
SamplingSampling
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Dual Tessellations
Voronoi Vertices: Centers Circumscribing Spheres 4 nuclei
Delaunay Tetrahedron
Voronoi Voronoi Delaunay Delaunay
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Delaunay Tetrahedron:
Set of 4 nuclei,
circumscribing sphere
not containing
any other nuclei
Space-Covering Complete
Set Delaunay Tetrahedra:
Delaunay Tessellation
Voronoi Tessellation &
Delaunay Tessellation:
Duals
Delaunay Tessellation
Delaunay Tetrahedra:
Natural Multidimensional Interpolation Volume
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• NN-neighbour Interpolation KernelNN-neighbour Interpolation Kernel
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Linear KernelLinear Kernel
DTFEDTFE
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Higher Order NN interpolation Linear DTFEHigher Order NN interpolation Linear DTFE
(Bernardeau & vdW 1996; Schaap & vdW 2000)(Bernardeau & vdW 1996; Schaap & vdW 2000)
Delaunay TessellationDelaunay Tessellation
Field Estimator Field Estimator (DTFE)(DTFE)
Large number of ObjectsLarge number of Objects
Dimensions higher > 2Dimensions higher > 2
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DTFE DTFE Operational Virtues:Operational Virtues:
Volume-weighted (<> Volume-weighted (<> mass-weighted)mass-weighted)
Field UniversalityField Universality
Dynamic Range & Spatial Dynamic Range & Spatial ResolutionResolution
Shape & Morphology Shape & Morphology SensitivitySensitivity
Void (structure) detection & Void (structure) detection & renderingrendering
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DTFE DTFE
Dynamic Range & Dynamic Range & ResolutionResolution
* DTFE resolves internal * DTFE resolves internal substructuresubstructure
over full range of over full range of scales presentscales present
in datain data
* Test: Soneira-Peebles * Test: Soneira-Peebles (fractal) model(fractal) model
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DTFE DTFE
Shape & Morphology Shape & Morphology SensitivitySensitivity
* DTFE retains the elongated or * DTFE retains the elongated or flattened flattened
geometry of geometry of anisotropic featuresanisotropic features
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Spine:Spine:
Singularities, Singularities, Morse complex & Morse complex &
watershedwatershed
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Spine of the Cosmic Web:Spine of the Cosmic Web: Morse complex & search for Morse complex & search for singularities singularities
Spine of the Cosmic Web:Spine of the Cosmic Web: Morse complex & search for Morse complex & search for singularities singularities
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Spine of the Cosmic Web:Spine of the Cosmic Web: Morse complex & search for Morse complex & search for singularities singularities
Spine of the Cosmic Web:Spine of the Cosmic Web: Morse complex & search for Morse complex & search for singularities singularities
Morse theory:topological structure well-behaved C2 field:
• singularities - minima, maxima, saddles• “flow” field:• critical net slope lines: connection singularities• saddles-maxima: spine of field • basin minima: watershed voids
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Density Field Flow LinesDensity Field Flow Lines
Density Field Flow LinesDensity Field Flow Lines
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Density Field Flow Lines:Density Field Flow Lines: SingularitiesSingularities
Density Field Flow Lines:Density Field Flow Lines: SingularitiesSingularities
Critical NetCritical Net saddles-maxima: ridgessaddles-maxima: ridges
Critical NetCritical Net saddles-maxima: ridgessaddles-maxima: ridges
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Spine of the Cosmic Web Spine of the Cosmic Web
Spine of the Cosmic Web Spine of the Cosmic Web
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Void Void Detection:Detection:
Watershed Void Watershed Void FinderFinder
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Particle distr. DTFE densiy
Median Filtered Watershed transf.
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WATERSHEDS : A cell is the union of points that are
topological closer to a certain minimum
Topological Distance: The path that connects two points via the
steepest slope: the path a water-droplet would take, when
running down a landscape
WatershedsWatershedsSegmentation:
A division of space in individual cellsA division of space in individual cells
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Following the water-flow into the distinctcatchment basins.
Each basin belongingto one individualminima defines oneregion
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Surface of Density Field
Local
MinimaLocal
Minima
Pierce the local Pierce the local minima, and let the minima, and let the
landscape sink landscape sink slowly in a tub of slowly in a tub of
water water
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Every time two different flooding basins meet we draw a dividing wall
Flooding the Density Field
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Final
segmentation
lines
Void
Patches
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Particle distr.
Watershed transf.
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Particle distr.DTFE density + WVF zoom-in:DTFE density +WVF +void orientation
void shape void orientationtidal shear orientation
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MMF:MMF:
MultiscaleMultiscaleMorphology AnalysisMorphology Analysis
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Multiscale Multiscale MorphologyMorphologyFilter Filter
MMF dissection of cosmic web
into sheets, filaments, clusters …
filament
cluster
sheet
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Scale Space Pyramids
Gaussian smooth keeping same number of pixels.
The ensemble of images is referred to as a scale space stack: it is analysed as a single object.
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Scale Space AnalysisScale Space AnalysisInspiration from Medical Imaging:
trace blood vessels, tumors, etc.
Florack, Kuijper et al.; Lindeberg et al.
Sato et al. 1997; Lorentz et al. 1997
Frangi et al. 1998 Multiscale vessel enhancement filter
scale
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Scale Space AnalysisScale Space Analysis
scale
• Smooth the field over the range of relevant scales
• Select the characteristic scale of a particular (local) morphological element
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Scale Space AnalysisScale Space Analysis
scale
• Smooth the field over the range of relevant scales
• Select the characteristic scale of a particular (local) morphological element
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MultiscaleMultiscale
MorpholoMorphologygy
Filter Filter
(MMF)(MMF)
Aragon-Calvo, Jones,
van de Weygaert &
van der Hulst 2007
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MMF MMF Filamentary Filamentary Cosmic WebCosmic Web
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Ph.D. thesis
Miguel Aragon-Calvo
2007
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Gray: filament particles
Black: feature compression
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Gray: filament particles
Black: feature compression
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Cosmic Web:Cosmic Web:Cluster-Filament Cluster-Filament ConnectionConnection
#filaments emerging from #filaments emerging from clusters clusters
Mass & Volume content Mass & Volume content
Web morphologiesWeb morphologies
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Cosmic Web:Cosmic Web:Cluster-Filament Cluster-Filament ConnectionConnection
Density distribution Density distribution
Morph. elements Morph. elements
Mass & Volume content Mass & Volume content
Web morphologiesWeb morphologies
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Cosmic WebCosmic Web Dynamics & Evolution
- Megaparsec Tidal Field (Cosmic Web theory Bond et al.) - determines weblike geometry & topology - intimate link clusters and web features - large-small scale interaction: alignment galaxy spins along filaments possible SDSS confirmation - alignment voids over > 30 Mpc
Analysis: Unbiased analysis anisotropy & hierarchy cosmic web: - Voronoi & Delaunay tessellations - (natural neighbour) DTFE density field reconstruction & interpolation - basis for geometric & topological analysis: - Morse complex, singularities & critical net: spine - Watershed : voids - Multiscale Morphology Filter : multiscale weblike patterns