Cosmostat day Machine Learning in Astrophysics

Date: January the 24th, 2019

Organizer:  Joana Frontera-Pons  <joana.frontera-pons@cea.fr>

Venue:

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 http://www.cosmostat.org/link/how-to-get-to-sap/ for detailed information on how to arrive.


On January the 24th, 2019, we organize the fourth day on machine learning in astrophysics at DAp, CEA Saclay. 

Program:

All talks are taking place at DAp, Salle Galilée (Building 713)

10:00 - 10:45h. TBD
10:45 - 11:15h. TBD
11:15 - 11:45h. TBD

12:00 - 13:30h. Lunch

13:30 - 14:00h. TBD
14:00 - 14:30h. TBD                                                            
14:30 - 15:00h. TBD
15:00 - 15:30h. TBD

15:30 - 16:00h. Coffe break

16:00 - 17:00h. Round table


 Previous Cosmostat Days on Machine Learning in Astrophysics :

CosmosClub: Sylvain Vanneste (16/11/2018)

Date: October 16th 2018, 2pm

Speaker: Sylvain Vanneste (LAL)

Title: Detecting CMB B-modes

Room: Kepler


Abstract

The discovery of the Cosmic Microwave Background (CMB) by Penzias and Wilson in 1964 was an important confirmation of the Big Bang theory. The CMB constitutes a background of photons emitted during the first instants of our Universe history, and still permeates it today. Since its discovery, numerous telescopes, balloon-born, or satellite experiments such as Planck, have made it possible to produce measurements and precise temperature maps of the CMB, of which we have been able to deduce important information about our Universe.
However, a piece of the cosmological puzzle is still missing: the inflation, corresponding to a short period during which the Universe would have seen its size growing exponentially. Inflation is a theory introduced to solve several major cosmological questions, and which, to date, has only been verified indirectly.
The inflation phase, however, should produce a stochastic background of primordial gravitational waves that may have left an imprint on the CMB. More particularly, these gravitational waves would induce the so-called B-modes patterns on the polarisation maps of CMB photons. The precise measurement of the B-modes, still undetected to this day, represents the most powerful probe of inflationary physics.
The B-modes expected signal is however of low intensity, and many additional experimental difficulties arise when aiming at measuring it. Dust from our own galaxy partially masks the CMB, and many models are developed to clean up galactic contaminations. The extraction and analysis of the measured data signal thus requires the development of precise statistical algorithms. These must take into account the complexity of the data produced, such as residual galactic contaminations, incomplete sky map coverage, as well as statistical and instrumental errors.
 

 

CosmosClub: Jia Liu (07/11/2018)

Date: November 7th 2018, 2pm

Speaker: Jia Liu (Princeton University)

Title: Cosmology in the nonlinear regime with massive neutrinos [slides]

Room: Kepler


Abstract

The non-zero mass of neutrinos suppresses the growth of cosmic structure on small scales. Since the level of suppression depends on the sum of the masses of the three active neutrino species, the evolution of large-scale structure is a promising tool to constrain the total mass of neutrinos and possibly shed light on the mass hierarchy. I will discuss recent progress and future prospects to constrain the neutrino mass sum with cosmology, with a focus on observables in the nonlinear regime.

CosmosClub: Chieh-An Lin (09/10/2018)

Date: October 9th 2018

Speaker: Chieh-An Lin (IfA, University of Edinburgh)

Title: Predicting weak-lensing covariance with a fast simulator


Weak lensing has been shown as an outstanding tool to constrain cosmology. The state-of-the-art studies have used the power spectrum and peak counts as estimators, and the combination of the two can break down parameter degeneracies and maximize the information extraction.

To constrain cosmology with both estimators, understanding the joint covariance is crucial. However, calculating it analytically seems to be intractable for peaks, and the empirical approach with N-body simulations will be expensive as the size of lensing surveys increase.

I will present a fast solution to solve this problem. The proposed approach simulates lognormal fields and halo models to predict lensing signals. We compared the resulting joint covariance with the one from a large number of N-body simulations and found an excellent agreement. In addition, our approach is orders of magnitude faster than N-body runs.

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

http://www.iap.fr/accueil/acces/acces.php


Participants

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

Program

 

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

Venue:

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 http://www.cosmostat.org/link/how-to-get-to-sap/ 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. 

Program:

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

Website: http://ecole-euclid.cnrs.fr/accueil-session-2018


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 pallas.py (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: ede2018.slack.com

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.