Résumé : These lectures will give a short introduction to the fundamentals of Bayesian inference and its application to simple but representative problems. Numerical methods such as Markov Chain Monte Carlo will be introduced and their practical workings illustrated. The Bayesian approach to model selection via Bayesian model comparison will be explained and contrasted with Frequentist hypothesis testing.

Résumé : Large amounts of invisible matter in the universe have been discovered in 1933 when the Swiss astronomer Fritz Zwicky measured the velocity dispersion of individual galaxies inside the Coma cluster. Zwicky determined for the first time the dynamical mass of that system and obtained a value more than a hundred times larger than the visible counterpart inferred from the luminosity of galaxies. The astronomical dark matter puzzle originates from this measurement. Since then, it has been steadily confirmed by a series of refined observations, performed at very different scales, which I will review in the first chapter. The non-baryonic nature of dark matter is one of the most intriguing results and has been confirmed by the Planck satellite. In the second part, I will concentrate on the bestiary of candidates provided by the theoretical extensions of the standard model of particle physics. After a brief introduction to supersymmetry and Kaluza-Klein theories, I will pay particular attention to the WIMP miracle. Chapter 3 is devoted to the searches for dark matter candidates, with particular emphasis on weakly interacting massive species, dubbed WIMPs. Direct and indirect detections will be reviewed. An excess in the energy distribution of cosmic ray positrons has been discovered in 2008 above 10 GeV, raising the tremendous hope that WIMPs were not just a fantasy. Interpreting that excess as a smoking gun evidence for dark matter particles is very tempting. However, that possibility has by now fallen into disfavor on the basis of arguments which I will discuss. The final part of the lecture deals with the results collected during the first run of the large hadron collider (LHC) and the lack of direct evidence for physics beyond the standard model. I will discuss how this impacts on the models of dark matter and the WIMP properties.

Bibliographie :

• For a review on the astronomical evidences for dark matter, see for instance
• F. Zwicky, Helvetica Physica Acta 6, 110 (1933)
• http://ned.ipac.caltech.edu/level5/Sept09/Einasto/frames.html
• http://www.learner.org/courses/physics/unit/pdfs/unit10.pdf
• For WIMP production in the early universe, see for instance
• B. W. Lee and S. Weinberg, Phys. Rev. Lett. 39, 165 (1977)
• P. Binetruy, G. Girardi and P. Salati, Nucl. Phys. B237, 285 (1984)
• https://lapth.cnrs.fr/micromegas/
• For direct and indirect searches for dark matter species, see for instance
• http://arxiv.org/pdf/1403.4495.pdf
• http://pos.sissa.it//archive/conferences/049/009/cargese_009.pdf
• http://arxiv.org/pdf/1004.1092.pdf
• For dark matter searches at the LHC, see for instance
• http://www.mpi-hd.mpg.de/phenocond/pdf/collider-dm.pdf
• http://moriond.in2p3.fr/J12/transparencies/14_Wednesday_am/malik.pdf
• https://kicp-workshops.uchicago.edu/DM-LHC2013/presentations.php

---

** Posters **

From dynamical models to cosmological observables (pdf) - Orest HRYCYNA, National Centre for Nuclear Research at Varsaw

Résumé : Dynamical systems methods are used to investigate global behavior of the FRW cosmological models with non-minimally coupled scalar field and constant potential function. We show that the system can be reduced to an autonomous three-dimensional dynamical system and additionally is equipped with an invariant manifold corresponding to an accelerated expansion of the universe.
Using this invariant manifold we find an exact solution of the reduced dynamics. Cosmological observational data are used to find constraints on the model parameters. Following the Peixoto theorem some conclusions about structural stability are drawn.

---

The nonlinear power spectrum of general Dark Energy models (pdf)- Santiago CASAS, Institute for Theoretical Physics, Heidelberg

Résumé : We find fitting functions that describe the nonlinear matter power spectrum obtained from the CoDECS N-body simulations in coupled Dark Energy models. The fitting functions are obtained for the case of a constant coupling between DM and DE, and an exponential scalar field potential. Their validity is demonstrated for all available simulations in the redshift range z=0-1.6 and wave modes below k= 10h = Mpc . These formulas can be used in principle to test the predictions of this cDE model in the nonlinear regime without the need for additional computing-intensive N-body simulations. In this paper we use these fitting functions to perform forecasts on the constraining power of future galaxy-redshift surveys on the coupling paramaeter, using the Fisher matrix method for weak lensing and the galaxy power spectrum

---

Viable cosmological solutions in massive bimetric gravity (pdf)- Frank KOENNIG, Ruprecht-Karls-Universität Heidelberg

Résumé : We present general conditions of viable cosmological solutions of massive bimetric gravity models and constrain the free parameters by comparing to the Union 2.1 supernovae catalog and linear perturbation observations. We point out that a bimetric model with a single free parameter predicts a simple relation between the equation of state and the density parameter, fits well the supernovae data and is a valid and testable alternative to ΛCDM. Additionally, we identify the conditions for a phantom behavior. However, confirming previous results, we find that this minimal model is unstable at early times at small scales and present possible ways to cure the instability

---

Stochastic Field Theory for Structure Formation  (pdf)- Florian FUEHRER, University Heidelberg

Résumé : I will describe how the effect of small scales on the structure formation on  large scales can be parametrized by effective fluid parameters and a stochas-  tic noise. In particular I will focus on how to constrain these terms. Using  a simplified, but still realistic, model gives very strong constrains on the allowed parameters. I will also elaborate on the Bispectrum and point out it’s  importance for testing effective field theory models for clustering.

---

How the cosmic web induces galaxy intrinsic alignments (pdf) - Sandrine CODIS, Institut d’Astrophysique de Paris

Résumé : Intrinsic alignments are believed to be the major source of systematics of the future generation of weak gravitational lensing surveys like Euclid or LSST.
Direct measurements of the alignment of the projected light distribution of galaxies in wide field imaging data seem to agree on a contamination at a level between a few per cent and ∼ 10 per cent of the shear correlation functions, although the amplitude of the effect depends on the population of galaxies considered. Given this dependency, it is difficult to use dark matter-only simulations as the sole resource to predict and control intrinsic alignments. The inherently anisotropic nature of the large-scale structure and its complex imprint on the shapes and spins of galaxies may prevent isotropic approaches from making accurate predictions. In this work, we show how the hydrodynamical simulation Horizon-AGN can be used to shed light on the level of intrinsic alignment that could possibly be a major source of systematic errors in weak gravitational lensing measurements. In particular, assuming that the spin of galaxies is a good proxy for their ellipticity, we discuss how they are spatially correlated and how they couple to the tidal field in which they are embedded.

---

Building up along cosmic filaments: accretion and mergers on galactic spins (pdf) - Charlotte Welker, Institut d'Astrophysique de Paris

Résumé : Over the past ten years, several numerical investigations have reported that large - scale structures, i.e. cosmic filaments and sheets, influence the kinematics and morphology of dark haloes and galaxies . Thus, i t has been shown t hat massive hal oes have their angular momentum ( spin ) preferentially perpendicular to their neigh b o ring filament and higher spin parameters while low - mass haloes tend to show a parallel orientation of the spin . Using the cosmological hydrodynamical Horizon - AGN simulation, we have recently uncovered a similar trend for galaxies : the AM of low - mass, rotation - dominated, blue, star - forming galaxies is preferentially aligned with their filaments, whereas high - mass, velocity dispersion - supported, red quiescent galaxies tend to possess an AM perpendicular to these filaments. Moreover, we were able to associate a transition mass to this cha nge in spin orientation, which loosely corresponds to the characteristic mass at which a halo extent becomes comparable to that of the vorticity quadrant in which it is embedded within its host filament. These predictions have recently received their first observational support (Tempel & Libeskind 2013). Analyzing Sloan Digital Sky Survey (SDSS) data, these authors uncovered a trend f or spiral galaxies to align with nearby structures, as well as a trend for elliptical galaxies to be perpendicular to them. The key idea that emerged from all these studies is that lighter galaxies might acquire most of their spin through secondary infall from their (aligned with th e filament) vorticity rich environment, while more massive galaxies would rather acquire a large fraction of theirs via orbital momentum transfer during merger events which mainly take place along the direction of the large scale filament closest to them . We have recently confronted this scenario to numerical data and uncovered the major influence of mergers and smooth accretion on the properties of galaxies, noticeably the re - orientation of galactic spins relative to cosmic filaments. I n this talk, I will revisit these significant findings with an emphasis both on exploring the physical mechanisms which drive halo’s and galactic spin swings and on quantifying how much mergers and smooth accretion re - orient these spins relative to cosmic filament s. After a brief review of recent achievement s on this topic , I will develop in details the dynamical scenario that has emerged from these studies and present the recent results that strongly support these mechanisms. In particular, I will analyze the effect of mergers and smooth accretion on spin orientation, spin magnitude, dispersion and morphology for haloes and galaxies. The latter is of particular interest since correlated galactic morphologies are expected to be a major source of error in weak gravitational lensing surveys. Eventually I will discuss potential tracers for prospective observational confrontation. If time, I will discuss the comparative influence of dry and wet mergers on the morphology of galaxies.

---

Non-Gaussianity within SKA Large Scale Structure Observations (pdf) - Mahmoud HASHIM, University of Western Cape

Résumé : None

---

Estimating masses of dwarf spheroidal galaxies (ppt) Klaudia KOWALCZYK, Nicolaus Copernicus Astronomical Centre

Résumé : None