Simulating the Universe Christine Corbett Moran, Irshad Mohammed, - PowerPoint PPT Presentation

Simulating the Universe Christine Corbett Moran, Irshad Mohammed, Manuel Rabold, Davide Martizzi, Doug Potter, Aurel Schneider Oliver Hahn, Ben Moore, Joachim Stadel Beyond LCDM, Oslo 2015 Romain Teyssier

Outline - N-body codes: where do we stand ? - accuracy - new solvers ? - Challenges in Modified Gravity calculations. - f(R) and MOND - predictions - Simulating baryonic effects. - feedback processes - the physics of clusters & groups - baryons as a nuisance Beyond LCDM, Oslo 2015 Romain Teyssier

N body simulations: the state of affairs EUCLID requires 1% accuracy up to k=10 h/Mpc in the theory. Different codes have different systematic effects (time integration). GADGET3 – large scale force with Fourier convolution and Particle Mesh – small scale force with tree code (multipole direct space convolution) PKDGRAV3 – large and small scale force with (fast multipole) tree code – periodic BC using Ewald summation (use of GPU acceleration) RAMSES – Particle Mesh with Adaptive Mesh Refinement – Direct Poisson solver with Multigrid acceleration Ongoing Euclid CosmoSim WG project identical GADGET initial conditions and output files code comparison beyond the 1% barrier Beyond LCDM, Oslo 2015 Romain Teyssier

Systematic effects in N body codes Schneider et al. 2015 in prep. linear non-linear Beyond LCDM, Oslo 2015 Romain Teyssier

Comparing to the Cosmic Emulator Schneider et al. 2015 in prep. Heitmann et al. 2014 Beyond LCDM, Oslo 2015 Romain Teyssier

Comparing to the Cosmic Emulator Dark Sky simulation (Skillman et al. 2014) Beyond LCDM, Oslo 2015 Romain Teyssier

Beyond N body codes ? The Vlasov approach Hahn & Angulo (2015), Hahn, Abel, Kaehler (2013) Beyond LCDM, Oslo 2015 Romain Teyssier

Cosmological simulations with modified gravity Viable models show small deviations (1-10%) with LCDM. Motivated theoretically by dark matter (e.g MOND) or dark energy (e.g. f(R)). A fully developed theory is required with at least: – time evolution of the expansion factor (homogeneous universe) – self-consistent initial random fluctuations – viable weak-field limit for the dynamics of the matter MOND (AQUAL): a non-linear Poisson equation MOND (QUMOND): 2 standard (linear) Poisson equations f(R) model : a non-linear Poisson equation and a standard linear Poisson solver Beyond LCDM, Oslo 2015 Romain Teyssier

Cosmological simulations with modified gravity Challenges for simulations with modified gravity models – direct or Fourier convolution approach not valid anymore – non-linear field solvers are slow and converge poorly – non-linear multigrid techniques; Raphson-Newton iterations MLAPM with f(R) solver on AMR (Zhao, Li, Koyama 2011) ECOSMOG: f(R) field solver for the AMR code RAMSES (Li et al . 2012) MG-GADGET: f(R) models for the GADGET code (Puchwein et al. 2013) Phantom of RAMSES: QuMOND for the RAMSES code (Lüghausen et al. 2014) RAyMOND: AQUAL (and QuMOND) for the RAMSES code (Candlish et al. 2015) … Beyond LCDM, Oslo 2015 Romain Teyssier

Simulations with f(R) modified gravity model Lombriser et al. 2012 Beyond LCDM, Oslo 2015 Romain Teyssier

Simulations with f(R) modified gravity model Zhao, Li & Koyama (2011) Beyond LCDM, Oslo 2015 Romain Teyssier

Zoom simulations with f(R) model z strong (F4) medium (F5) weak (F6) Λ CDM Corbett Corbett Moran et al. 2014 Beyond LCDM, Oslo 2015 Romain Teyssier

Zoom-in simulations with f(R) models Corbett et al. (2014) Beyond LCDM, Oslo 2015 Romain Teyssier

“Baryonic effects are too difficult to model” (18%) Very low efficiency of gas conversion into star. Small mass galaxies are dominated by stellar feedback. Large mass galaxies are governed by AGN feedback. Stellar-to-halo mass ratio Moster et al. (2010) Dekel & Silk (1986) Silk & Rees (1998) Beyond LCDM, Oslo 2015 Romain Teyssier

Dark matter cusp-to-core transformation Excellent fit of the dark matter profile with a pseudo-isothermal profile de Blok et al. (2001) Beyond LCDM, Oslo 2015 Romain Teyssier

Galaxy formation in groups and clusters Beyond LCDM, Oslo 2015 Romain Teyssier

Adiabatic hydrodynamics: 10% accuracy ? Rabold et al. in prep. Beyond LCDM, Oslo 2015 Romain Teyssier

Feedback models from SMBH in massive ellipticals - Thermal feedback (Sijacki et al. 2007; Booth & Schaye 2010; Teyssier et al. 2010): “thermal bombs” - Radiative feedback (Choi et al, 2012, 2014; Vogelsberger et al. 2013): dust-absorbed UV radiation from the accretion disk. - Jet feedback (Omma et al., Cattaneo & Teyssier, Dubois et al. 2010, Choi et al. 2014): injection of momentum in a jet-like geometry. - Cosmic ray feedback (Pfrommer at al. 2010; Oh et al, 2013): heating from Alfven waves excited by CR-induced instabilities. - Bubble feedback (Sijacki et al. 2007): buoyantly rising bubble with initial radius close to 50 kpc These models are related to the quasar mode (thermal, radiative) or to the radio mode (jet, CR, bubbles) of AGNs. Cosmological simulations with zoom-in or periodic boxes and around 1 kpc resolution. Beyond LCDM, Oslo 2015 Romain Teyssier

The effect of baryons on the halo mass Martizzi et al. 14 Martizzi et al. 14 RAMSES code Beyond LCDM, Oslo 2015 Romain Teyssier

Central galaxy stellar mass Martizzi + 14 Beyond LCDM, Oslo 2015 Romain Teyssier

Central galaxy stellar mass distribution Martizzi et al. 14 Kravtsov et al. 14 Beyond LCDM, Oslo 2015 Romain Teyssier

The effect of baryons on the halo mass Genel et al. 14 Vogelsberger et al. 14 AREPO code Beyond LCDM, Oslo 2015 Romain Teyssier

Analytical halo model for the matter power spectrum For each halo, we consider analytical models for each of the 3 components: gas, dark matter and the central galaxy Using simple analytical profiles, we apply the “halo model” methodology to compute the power spectrum. Main ingredients are: - mass of the central galaxy : abundance matching - size of the central galaxy : 0.015 of the viral radius - total gas mass versus total halo mass : free parameter - adiabatic contraction for CDM White (2004), Zhan & Knox (2004), Rudd et al. (2008), Guillet et al. (2010), Semboloni et al. (2011), van Daalen et al. (2011)… Good agreement with the zoom-in simulations of Martizzi et al. (2014) Beyond LCDM, Oslo 2015 Romain Teyssier

A simple model for the effect of AGN feedback Semboloni et al. (2011) Mohammed et al. (2015) Beyond LCDM, Oslo 2015 Romain Teyssier

A simple model for the effect of AGN feedback Beyond LCDM, Oslo 2015 Romain Teyssier

Cosmological parameters estimation Mock weak-lensing observation with 3 redshift bins (EUCLID-like) Mohammed et al. (2015) increase max. multipole Beyond LCDM, Oslo 2015 Romain Teyssier

Beating down baryonic effects ? Mohammed et al. (2015) Beyond LCDM, Oslo 2015 Romain Teyssier

Conclusions - N-body codes are 1% accurate below k=1 Mpc/h; 5% accurate between 1 and 10 Mpc/h. Do we need higher-order accurate N-body solvers ? Something else ? - Modified gravity solvers are getting more and more popular. Still slow and fragile. - Simulations with baryons are not even 10% accurate ! - Massive variations between codes and feedback models ! - AGN feedback models (when properly calibrated) can reproduce reasonably well the main properties of groups and clusters. - The effect of baryons reaches 10% (deficit) at k=20 Mpc/h. More ? - Cosmological parameters could in principle be fitted with 1% accuracy down to 1 arcmin if one uses an unbiased model. Beyond LCDM, Oslo 2015 Romain Teyssier