Lagrangian tessellations of large-scale N-body simulations

MXXL // Angulo et al (2012)
A new way of thinking about DM
simulations
Raul E. Angulo
Oliver Hahn (ETH, Zürich)
Tom Abel (SLAC/Stanford)
Abel et al (2012) – Analysis
Hahn et al (2013) – Simulation
Kaehler et al (2013) – Visualization
Angulo et al (2013a) – Baryons
Angulo et al (2013b) – WDM
Angulo et al (2013c) – Lensing
Hanh, Angulo & Abel (2014) – Refinement
Hanh, Angulo & Abel (2014) – Velocity
Nov 26th, 2013
Raul E. Angulo
CEFCA
Nov 26th, 2013
Raul E. Angulo
CEFCA
~8500 deg2
54 narrow, 2 broad band filters
width ~100A
Javalambre Photometric Local Universe Survey
10 intermediate/broad band
2 narrow band
Nov 26th, 2013
Raul E. Angulo
CEFCA
Infla
tion
Simulating the growth of dark matter structures
Properties of a WIMP (e.g. neutralino)
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Perturbations down to earth mass
Cold (almost no velocity dispersion)
Almost uniform in space
Only gravitational interactions
Kuhlen, Vogelsberger & Angulo 2012
A 3D surface embedded in a 6D space
Nov 26th, 2013
Raul E. Angulo
CEFCA
Nov 26th, 2013
Raul E. Angulo
CEFCA
Softening length prevents forces
from diverging, which would cause
large angle scatterings and two-body
interactions
Nov 26th, 2013
Raul E. Angulo
CEFCA
Two-fluid simulations
Artificially strong coupling between baryons and dark matter particles
Angulo, Hahn, Abel (2013)
Angulo et al (2013a)
Standard Runs
Standard Runs
FFT = Npart
Adaptive Softening
Nov 26th, 2013
Raul E. Angulo
CEFCA
Why it is so hard?
Small scale coupling quickly propagates to large scales
It is alleviated only by a strong suppression of the force resolution
Nov 26th, 2013
Raul E. Angulo
CEFCA
Two-fluid simulations
Baryons can not be neglected if 1% precision is desired for the P(k)/BAO
Angulo, Hahn, Abel (2013)
Redshift = 1
Nov 26th, 2013
Raul E. Angulo
CEFCA
Cold-vs-Warm Dark Matter
Properties of collapsed objects could
provide an insight into the properties of
the dark matter particle
A WDM model alleviates several
small-scale issues with CDM
Nov 26th, 2013
Raul E. Angulo
CEFCA
Artificial filament fragmentation
Problem known for more than 25 years!
Wang and White (2007)
Hot/Warm DM models are hard to simulate.
Thus, it is hard to make robust predictions.
No suppression of the mass function
Nov 26th, 2013
Raul E. Angulo
CEFCA
Why it is so hard?
Anisotropic compression in triaxial collapse
Noise in the 1D projected density field
Convergence is very slow
Npart^1/3
Nov 26th, 2013
Raul E. Angulo
CEFCA
A new way of thinking about DM
simulations
CDM forms continuous 3D surface
embedded in a 6D space
Properties of a WIMP (e.g. neutralino)
●
●
●
●
Perturbations down to earth mass
Cold (almost no velocity dispersion)
Almost uniform in space
Only gravitational interactions
From O. Hahn
Nov 26th, 2013
Raul E. Angulo
CDM forms continuous 3D surface
embedded in a 6D space
Kaehler et al (2012)
Nov 26th, 2013
Raul E. Angulo
Nov 26th, 2013
Raul E. Angulo
Hahn et al (2012)
Two representations of the same N-body data
Kaehler et al (2012)
Full rendering of tetrahedra
Adaptive-kernel smoothing
Nov 26th, 2013
Raul E. Angulo
Applications>
Strong Lensing
Velocity Fields
Warm Dark Matter
Substructures and strong lensing
CDM
WDM
Noise in convergence maps of the inner 0.6Mpc/h regions of a cluster
Nov 26th, 2013
Raul E. Angulo
Inverse of the magnification maps
Topology of the magnification depends on the CDM properties
Nov 26th, 2013
Raul E. Angulo
Iso-magnification contours
CDM
Nov 26th, 2013
WDM
Raul E. Angulo
The cumulative number of
convergence peaks
Nov 26th, 2013
Raul E. Angulo
Velocity Fields
Density
Divergence
Vorticity
Hahn, Angulo, Abel (2014)
Nov 26th, 2013
Raul E. Angulo
Velocity divergence and vorticity
power spectra
Jennings et al (2011)
Hahn, Angulo, Abel (2014)
Nov 26th, 2013
Raul E. Angulo
Vorticity in a slice trough the
center of a DM halo
Vorticity is generated in the caustics of filaments and halos
Vorticity profile
Hahn, Angulo, Abel (2014)
Nov 26th, 2013
Raul E. Angulo
Artificial filament without fragmentation
Lagrangian Tessellation can be coupled with a Poisson solver
Angulo, Hahn, Abel (2013b)
L=80 Mpc/h
1 billion DM particles
L-Gadget 3 code (MXXL)
Nov 26th, 2013
Raul E. Angulo
CEFCA
Artificial filament fragmentation
Hot/Warm DM models are hard to simulate numerically.
Thus, it is hard to make robust predictions.
Nov 26th, 2013
Raul E. Angulo
CEFCA
Nov 26th, 2013
Raul E. Angulo
CEFCA
Nov 26th, 2013
Raul E. Angulo
CEFCA
Angulo, Hahn & Abel 2013b
Angulo, Hahn & Abel 2013b
Nov 26th, 2013
Raul E. Angulo
CEFCA
WDM structure formation without fragments
Halos of different masses are at different stages of formation
Angulo, Hahn & Abel 2013
Nov 26th, 2013
Raul E. Angulo
CEFCA
A new way of thinking of DM simulations
Tetrahedron-based density estimates are in principle
noiseless and fully track the distortion of initial
phase-space volume elements.
First direct measurements of the WDM halo mass function
below the cut-off scale
Improved predictions for the spacial distribution of the DM,
and its associated velocity field and lensing signal.
Nov 26th, 2013
Raul E. Angulo
CEFCA