tracing the halo – cosmic web connection marius cautun kapteyn astronomical institute rien van de...
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Tracing the Tracing the Halo – Cosmic WebHalo – Cosmic Web
ConnectionConnection
Marius CautunMarius Cautun
Kapteyn Astronomical InstituteKapteyn Astronomical Institute
Rien van de Weygaert, Wojciech Hellwing, Rien van de Weygaert, Wojciech Hellwing,
Carlos Frenk, Bernard J. T. JonesCarlos Frenk, Bernard J. T. Jones
September 6th 2012CosmoComp 2012, Trieste
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Sloan Digital Sky Survey galaxies
Introduction
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Outline
I - The NEXUS+ algorithm
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Outline
II – Halos and the Cosmic Web
I - The NEXUS+ algorithm
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I – The NEXUS+ Algorithm
Challenges:
• Multiscale distribution
• No clear defined boundaries
• Orders of magnitude variation in the density field
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The NEXUS+ algorithmThe NEXUS+ algorithm
1. Apply a filter to the input field.
filter
I – The NEXUS+ Algorithm
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The NEXUS+ algorithmThe NEXUS+ algorithm
1. Apply a filter to the input field.
I – The NEXUS+ Algorithm
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1. Apply a filter to the input field.
2. Compute the Hessian of the filtered field ff.
2
1 2 3
( )( ) has eigenvalues: ij
i j
f xH x
x x
The NEXUS+ algorithmThe NEXUS+ algorithm
I – The NEXUS+ Algorithm
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The NEXUS+ algorithmThe NEXUS+ algorithm
1. Apply a filter to the input field.
2. Compute the Hessian of the filtered field ff.
3. Use the Hessian eigenvalues to assign an environment signature to each point.
I – The NEXUS+ Algorithm
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The NEXUS+ algorithmThe NEXUS+ algorithm
1. Apply a filter to the input field.
2. Compute the Hessian of the filtered field ff.
3. Use the Hessian eigenvalues to assign an environment signature to each point.
I – The NEXUS+ Algorithm
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The NEXUS+ algorithmThe NEXUS+ algorithm
1. Apply a filter to the input field.
2. Compute the Hessian of the filtered field ff.
3. Use the Hessian eigenvalues to assign an environment signature to each point.
4. Repeat steps 1-3 for a range of filter scales.
increasing filter size
I – The NEXUS+ Algorithm
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The NEXUS+ algorithmThe NEXUS+ algorithm
1. Apply a filter to the input field.
2. Compute the Hessian of the filtered field ff.
3. Use the Hessian eigenvalues to assign an environment signature to each point.
4. Repeat steps 1-3 for a range of filter scales.
5. Combine the environmental signatures of each scale to get a scale independent result.
I – The NEXUS+ Algorithm
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The NEXUS+ algorithmThe NEXUS+ algorithm
1. Apply a filter to the input field.
2. Compute the Hessian of the filtered field ff.
3. Use the Hessian eigenvalues to assign an environment signature to each point.
4. Repeat steps 1-3 for a range of filter scales.
5. Combine the environmental signatures of each scale to get a scale independent result.
6. Use physical criteria to identify the valid clusters, filaments and walls.
I – The NEXUS+ Algorithm
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NEXUS+ resultsNEXUS+ results
I – The NEXUS+ Algorithm
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Cosmic Web evolutionCosmic Web evolution
I – The NEXUS+ Algorithm
volume rendering.Using the data from CosmoGrid simulation (Ishiyama+ 2011).
1 320 20 2 ( )Mpc h
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Halos and environmentsHalos and environments
II – Halos and the Cosmic Web
Halo mass functionHalo fraction
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Halos and environmentsHalos and environments
II – Halos and the Cosmic Web
Angular momentum direction Major axis of halo shape
Aragon-Calvo+ (2007), Hahn+ (2007), Codis+ (2012), Trowland+ (2012)
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Environment characteristicsEnvironment characteristics
II – Halos and the Cosmic Web
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Environment characteristicsEnvironment characteristics
Filament diameter
II – Halos and the Cosmic Web
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Environment characteristicsEnvironment characteristics
Filament diameter
II – Halos and the Cosmic Web
Filament linear density
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II – Halos and the Cosmic Web
Dependence on filamentary density
Halo angular momentum vs. environmentHalo angular momentum vs. environment
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II – Halos and the Cosmic Web
Closer to home: Milky WayCloser to home: Milky Way
Wang, Frenk, Navarro, Gao and Sawala (2012):
• 3 MW satellites with maximum velocity > 30 km/s
120
120
40% for a MW mass 10
5% for a MW mass 2·10
M
M
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II – Halos and the Cosmic Web
Closer to home: Milky WayCloser to home: Milky Way
Wang, Frenk, Navarro, Gao and Sawala (2012):
• 3 Milky Way (MW) satellites with maximum velocity > 30 km/s
120
120
40% for a MW mass 10
5% for a MW mass 2·10
M
M
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II – Halos and the Cosmic Web
Substructure and environmentSubstructure and environment
MW resides in a wall-like environment (Tully+ 2008)
For MW-like halos in the Millennium 2 simulation:
90% in filaments
10% in walls
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II – Halos and the Cosmic Web
Substructure and environmentSubstructure and environment
7% of halos in filaments
14% of halos in walls
Number of subhalos with maximum velocity larger than 30km/s for a MW-like halo with 200km/s.
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ConclusionsConclusions
• The NEXUS+ algorithm: a tool for multiscale and automatic Cosmic Web environment detection.
• Very successful in following the evolution of the cosmic environments.
• Ideal tool for measuring the influence of the Cosmic Web on dark matter halos and galaxies.
• Understanding how the Cosmic Web influences the formation and evolution of halos and galaxies.
II – Halos and the Cosmic Web
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II – Halos and the Cosmic Web