Euclid – France atelier/workshop gravitational lensing

Date: October 22, 2018

Organizer:  Martin Kilbinger & Karim Benabed

Venue: IAP,  98bis bd Arago, 75014 Paris. Salle Entresol

Local information


Martin Kilbinger
Karim Benabed
Sandrine Codis
Eric Jullo
Francis Bernardeau
Yohan Dubois
Santiago Casas
Raphael Gavazzi
Alain Blanchard
Patrick Hudelot
Calum Murray
Matteo Rizzato
Samuel Farrens
Alexandre Barthelemy
Austin Peel
Nicolas Martinet
Morgan Schmitz
Virginia Ajani
Henry McCracken
Peter Taylor
Bertrand Morin
Céline Gouin



10:00   Café
10:30   Martin Kilbinger                Welcome, introduction, goals of the meeting, resources
10:45   Matteo Rizzato                   Information content in the weak lensing bispectrum
11:15   Eric Jullo                                 WLSWG work package “Galaxy-galaxy lensing”
11:45   Alexandre Barthelemy    One-point statistics of weak lensing maps
12:15    Peter Taylor                         k-cut Cosmic Shear: Tunable Power Spectrum Sensitivity to Test Gravity
12:45   Henry Joy McCracken    Euclid VIS activities and weak lensing requirements
13:00   Lunch
14:15   Austin Peel                           Peak counts: breaking degeneracies & machine learning
14:45   Nicolas Martinet               WL peak/mass mapping/shear calibration
15:15   Céline Gouin                       The impact of baryons on WL statistics
15:45   Bertrand Morin                  COSEBIs - Implementation of cosmic shear E-/B- modes
16:15   Martin Kilbinger, all          WL projects in Euclid-France, discussion, future plans
17:15   End



French-Chinese Days on Weak Lensing

Date: October 4-5, 2018

Organizer:  Jean-Luc Starck and Martin Kilbinger


Local information

CEA Saclay is around 23 km South of Paris. The astrophysics division (DAp) is located at the CEA site at Orme des Merisiers, which is around 1 km South of the main CEA campus. See for detailed information on how to arrive.

On 4 and 5 October, 2018, we are organizing the first French-Chinese weak-lensing meeting at DAp, CEA Saclay. 


All talks are taking place at DAp, Salle Kepler (Building 709)

Thursday, October 4

9:30 - 10:00h.  Café

10:00 - 10:15h.    Welcome & introductions

10:15 - 10:45h.   Hu Zhan,   Overview of CSS-OS

10:45 - 11:15h.   Martin Kilbinger, Overview of CFIS Weak Lensing

11:15 - 11:45h.  Jun Zhang, Fourier_Quad,  a shear measurement method in Fourier Space

11:45 - 14:00h.  Lunch at the Rotonde

14:00 - 14:30h. Morgan Schmitz,  PSF Modeling using a Graph Manifold

14:30 - 15:00h. Chengliang Wei, A full sky WL simulation with semi-analytic galaxy formation 

15:00 - 15:30h. Jean-Luc Starck,  WL Mass Mapping

15:30 - 16:00h. Zuhui Fan,  WL peak statistics

16:00 - 16:30h. Austin Peel,  Cosmology with Mass Maps

Friday, October 5

9:30 - 10:00h.      Café

10:00 - 10:30h.   Sam Farrens,   The CFIS pipeline

10:30 - 11:00h.  Ran Li,  Lensing studies of sub-structures

11:00 - 11:30h.  Axel  Guinot,  Preliminary CFIS results

11:30 - 12:00h.  Liping Fu, Shear measurement from VOICE deep survey

12:00 - 14:00h. Lunch at Les Algorithmes

14:00 - 14:30h. Jean-Charles Cuillandre, The Euclid mission and ground-based observations

14:30 - 15:00h.  Huanyuan Shan: KiDS WL studies (via skype)

15:00 - 15:30h.  Alexandre Bruckert, Machine learning for blended objects separation

15:30 - 16:00h.   Rebeca Araripe Furtado Cunha,  Optimal Transport and PSF Modeling

16:00 -  17:00h. Discussion


École Euclid de cosmologie 2018

Date: August 20 - September 1, 2018

Venue: Roscoff, Bretagne, France


Lecture ``Weak gravitational lensing'' (Le lentillage gravitationnel), Martin Kilbinger.

Find here links to the lecture notes, TD exercises, "tables rondes" topics, and other information.

  • Resources.
    • A great and detailed introduction to (weak) gravitational lensing are the 2005 Saas Fee lecture notes by Peter Schneider. Download Part I (Introduction to lensing) and Part III (Weak lensing) from my homepage.
    • Check out Sarah Bridle's video lectures on WL from 2014.
  • TD cycle 1+2, Data analysis.
    1.  We will work on a rather large (150 MB) weak-lensing catalogues from the public CFHTLenS web page. During the TD I will show instructions how to create and download this catalogue. These catalogues will also be available on the virtual machine for the school.
      If you like, you can however download the catalogue on your laptop at home. Please have a look at the instructions in the TD slides.
    2. If you want to do the TD on your laptop, you'll need to download and install athena (the newest version 1.7). Available on the VM.
    3.  For one of the bonus TD you'll need a new version of (v 1.8beta). Download it here. Available on the VM.
  • Lecture notes and exercise classes.  You can already download the slides in one file (40 - 60 MB), but be ware that the content will still change slightly until the classes.
    • Part I (Cycle 1):    [all | day 1 (1/6)  |   day 2 (2/6) |  day 3 (3/6)]
    • Part II (Cycle 2):  [all | day 1 (4/6)   |   day 2 (5/6)  | day 3 (6/6)]
    • TD:                             [1/2 and 2/2]
    • Table Ronde sujet
  • Slack channel:

CosmosClub: Benjamin l’Huillier (13/09/2018)

Date: September 13th 2018

Speaker: Benjamin l'Huillier (Korea Astronomy and Space Science Institute)

Title: Cosmological structure formation in LCDM and beyond: Testing LCDM with N-body simulations and advanced statistical methods [slides]

The current concordance cosmological paradigm relies on a few assumptions: gravity is described by General Relativity, the Universe is Homogeneous and Isotropic on large scales, and a phase of inflation in the early Universe. Under these assumptions, the solution to the Einstein Equations is the Friedmann—Lemaître—Robertson—Walker (FLRW) metric, a general metric describing an expanding Universe. Observationally, the Universe seems flat, dominated by dark energy, thought to be responsible for the late-time acceleration of the Universe, and by a smooth dark matter component. Albeit reasonable, these are all assumptions. Therefore, it is important to test these assumptions in order to falsify the concordance model. 
In the first part of my talk, I will show how to probe extension to the LCDM paradigm via cosmological simulations (Modified Gravity and dark energy, primordial power spectrum): how do haloes form in modified gravity? can we use the large-scale structure to probe features in the primordial power spectrum?
I will then move on to the falsification of the concordance model via model-independent tests of the concordance model from the data at the background (FLRW metric, flatness, Lambda dark energy) and the perturbation (growth rate gamma), and obtain model-independent constraints on some key cosmological parameters. 

CosmosClub: Santiago Casas (09/07/2018)

Date: July 9th 2018

Speaker: Santiago Casas (CEA Saclay)

Title: Dark Energy with Euclid

Euclid is an ESA medium-class mission expected to launch in 2020 that will map the geometry of the Universe by imaging 10^9 galaxies and measuring 10^7 galaxy redshifts in 15000 square degrees of the sky. This will provide us detailed information about the accelerated expansion, the evolution of large-scale structure and the matter-energy content of the Universe up to a redshift of about z≈2.
In this talk, I will review how the main probes of Euclid, namely galaxy clustering and weak lensing, will be able to constrain theories beyond the standard cosmological ΛCDM model and how we will be able to pin down the equation of state of dark energy with about 1% precision. Galaxy clustering measures mainly the movement of tracers along geodesics, while weak lensing is an almost direct mapping of the gravitational potentials at large scales. Using both of these observables, we can obtain valuable information about the growth of perturbations and the geometrical quantities of the Universe and therefore constrain the properties of General Relativity. Since the measurements of Euclid will also give insights on the properties of dark matter and neutrinos at cosmological scales, I will also show how we can measure non-standard couplings between matter species and dark energy and how we can give tight constraints on many alternative theories of gravity.

CosmosClub: Viviana Niro (25/06/2018)

Date: June 25th 2018

Speaker: Viviana Niro (University of Heidelberg)

Title: Galaxy rotation curves in modified gravity models [slides]

I'll present the possibility that galaxy rotation curves can be explained in the framework of modified gravity models. A Yukawa term is considered in the gravitational potential and dark matter is included in the fit.
Using a set of 40 galaxy rotation curves data from the SPARC catalogue, I'll present constraints on the strength, β, and the range, λ, of the Yukawa fifth force. The global best-fit is found to be β=0.34±0.04 and λ=5.61±0.91 kpc and the dark matter content is on average 20% smaller than in the standard gravity parametrization. The Bayesian evidence for a NFW profile and a Yukawa term is higher than 8σ with respect to the case without the Yukawa term.

CosmosClub: Alessio Spurio Mancini (03/05/2018)

Date: May 3rd 2018

Speaker: Alessio Spurio Mancini

Title: Weak gravitational lensing as a (3D) probe of gravity


Cosmic shear, the weak gravitational lensing effect caused by the
large-scale structure, is one of the primary probes to test gravity on
cosmological scales with current and future surveys. In particular,
cosmic shear is sensitive to both standard GR cosmological parameters
and those that describe modified theories of gravity, such as those
belonging to the Horndeski class. These models include the majority of
universally coupled extensions to ΛCDM with one scalar degree of freedom
in addition to the metric, which are still in agreement with current
In this talk I will discuss some aspects concerning the constraining
power of current and future cosmic shear datasets on this broad class of
theories. I will compare in particular two main techniques to analyse a
cosmic shear survey: a tomographic method, where correlations between
the lensing signal in different redshift bins are used to recover
redshift information, and a 3D approach, where the full redshift
information is carried through the entire analysis. Due to its increased
amount of redshift information, a future 3D analysis can constrain both
standard gravity and Horndeski theories better than a tomographic one,
in particular with a decrease in the errors on the Horndeski parameters
of the order of 20%.