Structure Formation in numerical simulations

Fabio Iocco

School on DM�ICTP-SAIFR

4/7/16

ICTP-SAIFR IFT-UNESP

São Paulo

Summary of past week •  Evidence and properties of DM (What is DM?)

•  Production mechanisms, classes of models

•  How to recognize SUSY / new-physics in colliders

•  The distribution of DM in space (on big scales)

•  Halo formation and distribution theory

But colliders not enough for DM

Structure of this week •  Concentrate on some more specific models (WIMPs)

•  Reconstruction of different properties (through different methods: indirect, direct)

•  Need for astrophysics, and some nuclear physics

•  Introduce the basics of some of the above (lensing, CRs)

•  Describe our theoretical (from Simulations) expectations and observational evidence for DM distribution

Purpose of this lecture

•  Make you familiar with jargon, results, and problems of a specific field:

numerical simulations.

•  Stimulate you to a critical thinking: tool to interpret them

(do NOT repeat mantras).

Formation of structures: Dissipationless N-body simulations

(or Dark Matter Only : DMO)

Discrete grids in numerical

solvers

Resolution as a constraint

Let’s have a look at it

•  Aquarius: evolution movie (MW size HIres)

•  Via Lactea: evolution movie (MW halo, HIres)

•  Millennium : flythrough at z=0

•  MillenniumII : flythrough at z=0

“Observables” from sims

•  # of halos (per mass, per redhisft)

•  Matter distribution on different scales

•  …

•  Any other idea, anybody?

The DM profile of halos

Same profile over several orders of magnitude in halo mass Generalised NFW

g Dutton + Schaller slides’ at MITP workshop

https://indico.mitp.uni-mainz.de/event/50/timetable/#20160502

NFW profile seems “universal”, but…

Dutton + Schaller slides’ at MITP workshop https://indico.mitp.uni-mainz.de/event/50/timetable/#20160502

The core/cusp problem

The missing satellite problem

Caveats

•  Where are the flaws in what I mentioed so far?

•  Speak up, please.

The big step ahead: baryons (fiat lux)

Marinacci + Oñorbe slides’ at MITP workshop https://indico.mitp.uni-mainz.de/event/50/timetable/#20160510

Core/cusp revisited (with “g-astro” simulations)

Core/cusp revisited (with “g-astro” simulations)

Same in a more complicated plane

Dutton + Schaller slides’ at MITP workshop https://indico.mitp.uni-mainz.de/event/50/timetable/#20160502

Comparison in a more complicated plane

Dutton + Schaller slides’ at MITP workshop https://indico.mitp.uni-mainz.de/event/50/timetable/#20160502

Comparison in a more complicated plane

Dutton + Schaller slides’ at MITP workshop https://indico.mitp.uni-mainz.de/event/50/timetable/#20160502

Too big to fail “problem”

Garrison-Kimmel + 2014: arXiv 1404.5313

Testing predictions against observations: state of the art

Katz + 2016: arXiV 1605.05971

Testing predictions against observations: state of the art

Katz + 2016: arXiV 1605.05971