PhD subjects

Dernière mise à jour : 02-12-2016

16 sujets IRFU

«««

• Astrophysics

 

Tidal dissipation in stars: angular momentum transport and magnetism

SL-DRF-17-0546

Research field : Astrophysics
Location :

Service d'Astrophysique

Laboratoire Dynamique des Etoiles et de leur Environnement (LDEE)

Saclay

Contact :

Stéphane MATHIS

Starting date : 01-10-2017

Contact :

Stéphane MATHIS

CEA - DRF/IRFU/SAp/LDEE

0169084930

Thesis supervisor :

Stéphane MATHIS

CEA - DRF/IRFU/SAp/LDEE

0169084930

Since the discovery of the first exoplanet around a solar-type star in 1995 (Mayor & Queloz 1995), a revolution is occurring in Astrophysics. More than 3000 exoplanets have been discovered and characterised around host stars of different masses and ages. The orbital architecture of these planetary systems is strongly different from the one of our Solar system. These groundbreaking discoveries change the paradigm for the understanding of the formation, the evolution and the stability of star-planet systems among which our own Solar system.



For short-period planets already discovered and those, which will be discovered and characterised by the forthcoming space missions CHEOPS (ESA) and TESS (NASA) in 2018 and PLATO (ESA) in 2024 (in which researchers of the Laboratory AIM – Astrophysics division of CEA are strongly involved), the host stars play a key role. Indeed, close planets induce in these stars complex tidal flows (such as oceanic tidal waves excited on the Earth by the combined lunar and solar tides). Their dissipation modifies the orbits of close planets and can influence the rotational dynamics of the stars (Bolmont & Mathis 2016). To understand the evolution of close star-planet systems, it is thus mandatory to build realistic ab-initio models of tidal waves and of their dissipation (e.g. Zahn 1975, Ogilvie & Lin 2004-07, Ogilvie 2013) as a function of the structural and dynamical properties of the host star. Indeed, it has been demonstrated that tidal dissipation in stars vary over several orders of magnitude as a function of the stellar mass, age, rotation and differential rotation (e.g. Mathis 2015, Mathis et al. 2016, Baruteau & Rieutord 2013, Guenel et al. 2016). Moreover, these properties of the dissipation strongly impact systems’ orbital and rotational evolution (e.g. Bolmont & Mathis 2016).



The objective of this PhD project is to model for the first time tidal waves dissipation in low-mass stars with taking into account the internal transport of angular momentum they induce (Favier et al. 2014) and magnetic fields (e.g. Wei 2016), particularly in stellar convective envelopes which are the seat of a dynamo action. The framework of this project is the European ERC project SPIRE (Stars: dynamical Processes driving tidal Interactions, Rotation and Evolution) within the Laboratory of the Dynamics of Stars and their Environment, one of the leading group in this research area, in close collaboration with the Institute of Astrophysics and Planetology (University of Toulouse), the Geneva University (Switzerland) and the Universities of Leeds and Cambridge (UK). The objective is to provide key theoretical predictions to accompany and ensure the best scientific exploitation of future space missions such as CHEOPS, TESS and PLATO.



Bibliography :

- Baruteau & Rieutord 2013, Journal of Fluid Mechanics, 719, 47

- Bolmont & Mathis 2016, Celestial Mechanics and Dynamical Astronomy, 126, 275

- Guenel, Baruteau, Mathis & Rieutord 2016, Astronomy & Astrophysics, 589, A22

- Favier, Barker, Baruteau, Ogilvie, 2014, Monthly Noticies of the Royal Astronomical Society, 439, 845

- Mathis 2015, Astronomy & Astrophysics, 580, L3

- Mathis, Auclair-Desrotour, Guenel, Gallet, Le Poncin-Lafitte 2016, Astronomy & Astrophysics, 592, 33

- Mayor & Queloz 1995, Nature, 378, 355

- Ogilvie 2013, Monthly Noticies of the Royal Astronomical Society, 429, 613

- Ogilvie & Lin 2004, The Astrophysical Journal, 610, 477

- Ogilvie & Lin 2007, The Astrophysical Journal, 661, 1180

- Wei 2016, The Astrophysical Journal, 828, 30

- Zahn 1975, Astronomy & Astrophysics, 41, 329

The transient Universe with MeerKAT

SL-DRF-17-0325

Research field : Astrophysics
Location :

Service d'Astrophysique

Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie (LEPCHE)

Saclay

Contact :

Stéphane CORBEL

Starting date : 01-09-2017

Contact :

Stéphane CORBEL

Université Paris 7 - DRF/IRFU/SAP/LEPCHE

01 69 08 45 62

Thesis supervisor :

Stéphane CORBEL

Université Paris 7 - DRF/IRFU/SAP/LEPCHE

01 69 08 45 62

More : http://www.ast.uct.ac.za/thunderkat

In 2017, a novel Observatory will come online. The South African SKA Project is currently building MeerKAT, a precursor radio telescope to the Square Kilometre Array (SKA). MeerKAT will consist of an array of 64 antennas and will be the most sensitive cm-radio telescope in the southern hemisphere. MeerKAT will be incorporated into the SKA1-MID component of the SKA around 2020, when the SKA1-MID array will be extended to around 200 antennas spread over a maximum baseline of 150 km.



Several MeerKAT Large Survey Projects (MLSPs) were selected in areas of key scientific interest closely related to the SKA science case. ThunderKAT is the MeerKAT LSP for image-domain (explosive) radio transients. A nominal 3000 h of time have been awarded to ThunderKAT over a 5 year period (2017-2021) of MeerKAT science operation. In addition, ThunderKAT will have commensal data access to all MeerKAT LSPs to search for synchrotron radio transients in real-time, effectively increasing the discovery-space of rare radio transients by a factor of 10.



ThunderKAT on MeerKAT will tackle all aspects of transient emission associated with accretion and explosive events. Through a comprehensive and complementary programme of surveying and monitoring Galactic synchrotron transients (across a range of compact accretors and a range of other explosive phenomena) and exploring distinct populations of extragalactic synchrotron transients (microquasars, supernovae and possibly yet unknown transient phenomena) – both from direct surveys and commensal observations – we will revolutionise our understanding of the dynamic and explosive transient radio sky.

Study of dark energy with quasar Lyman-alpha forests from eBOSS survey

SL-DRF-17-0232

Research field : Astrophysics
Location :

Service de Physique des Particules (SPP)

Groupe Bao

Saclay

Contact :

Jean-Marc LE GOFF

Starting date : 01-10-2017

Contact :

Jean-Marc LE GOFF

CEA - DRF/IRFU

01 6908 3962

Thesis supervisor :

Jean-Marc LE GOFF

CEA - DRF/IRFU

01 6908 3962

Quasar Lyman-alpha forests probe the hydrogen density along the lines of sight of the quasars, providing a measure of the baryonic acoustic oscillation (BAO) scale in the hydrogen correlation function. This BAO scale is a standard ruler that provides a measurement of the expansion rate of the Universe, therefore constraining dark energy models. The BAO scale was measured for the first time in the Lyman-alpha forest by SDSS III / BOSS. In the framework of SDSS IV / eBOSS, we propose first to measure the cross correlation between the quasar positions and the Lyman-alpha forest. Data taking started in 2014 and will last until 2019 or 2020, allowing the PhD student to have all the data in hand. Then the BAO scale should be extracted from the correlation function and the result used to study dark energy models. The student will also participate to the development of quasar spectra simulations with a physical correlation. A large set of simulations will have to be produced. This simulations will be developed both for eBOSS and for DESI, one of the next generation survey.

The student will be in a favorable situation, since the French teams (APC and CEA Saclay) play a leading role in the Lyman-alpha analysis in SDSS. He will develop his knowledge and capabilities in cosmology, statistics, data analysis and fitting, systematic studies, use of mathematical tools such as discrete Fourier transforms, and computer science: Python and possibly C and C++, dealing with a large amount of data and use of CPU farms. He will present his work in English in weekly teleconferences and collaboration meetings in Usa and Europe.

The physics of giant star-forming regions in primordial galaxies from a synergy of observations and simulations

SL-DRF-17-0387

Research field : Astrophysics
Location :

Service d'Astrophysique

Laboratoire de Cosmologie et d'Evolution des Galaxies (LCEG)

Saclay

Contact :

Emanuele DADDI

Frédéric BOURNAUD

Starting date : 01-09-2017

Contact :

Emanuele DADDI

CEA - DSM/IRFU/SAp/LCEG

Thesis supervisor :

Frédéric BOURNAUD

CEA - DRF/IRFU/SAp/LCEG

01 69 08 55 08

More : http://irfu.cea.fr/SAp

The morphology of star forming galaxies in the distant Universe, at the peak of their activity at redshift z=1-3, is remarkably different from that of nearby spirals. They have irregular morphologies, often dominated by giant star forming regions, known as star forming clumps. These clumps reach remarkably large sizes and masses, orders of magnitude larger than molecular clouds and star clusters in our Galaxy. This peculiarity of high-redshift star-forming galaxies is thought to be driven by their very large gas fractions and strong turbulence, compared to the local Universe: gas-rich galaxies can become violently unstable and fragment in such giant clumps.

However, despite several years of studies by many groups worldwide, a quantitative understanding of the nature and physical properties of these clumps is still lacking both from the theoretical and observational point of view. Hotly debated topics of contending remain, regarding the distribution of clumps masses, star formation rates, sizes, clumps formation rates and lifetime. More importantly, it remains unknown whether they survive stellar feedback processes, in which case they can drive the growth of galactic bulges and the fueling of supermassive black holes at the center of galaxies. In numerical simulations, many teams at different institutions reach wildly different conclusions, mostly related to discrepant implementation for feedback and regulation in the physics of star formation.



We propose a PhD project to explore a state of the art approach to this topic by simultaneously tracking 3 complementary lines of research:

1) physical characterization of clumps properties from observations, done for the first time with maps of physical parameters (maps of the stellar mass, maps of the star formation rate distribution), and with stellar mass limited (complete) samples of distant galaxies from HST data in CANDELS/UDF/FF.

2) systematic comparison with simulated maps from a large number of competing teams in the community with which we have collaborative relations, in order to obtain objective understanding of consistencies or differences between observations and various simulation dataset.

3) running suites of very high resolution numerical simulations with an improved modelling of star formation physics, in particular using adaptive-resolution hydrodynamic codes and “zooming” on the giant star-forming clumps, to get a more predictive modelling of when and where new stars formed, and how the turbulent interstellar medium reacts to their feedback processes.



These complementary lines will bring a robust understanding of the nature of the giant clumps, the violent instabilities in primordial galactic disks, and their role in shaping disks, bulges and central black holes. They will also provide a new, independent way to constrain the gas fraction in galaxies at various epochs, which is another highly debated issue and crucial to constrain theoretical galaxy formation models. The proposed work will also ideally prepare future developments with the use of JWST, which will image the mass distribution in primordial galaxies, and their ionized gas content, and comparison to forthcoming ALMA data probing the various gas phases in young galaxies. The detailed understanding of star formation processes in primordial galaxies will also be a strong asset to understand the relics in old stellar populations of nearby galaxies, in the context of deep morphology surveys and the Legacy science of EUCLID. The proposed thesis will also employ numerical simulations performed on the largest supercomputers in France (GENCI) and Europe (PRACE).

Real time analysis of the CTA transient sky

SL-DRF-17-0566

Research field : Astrophysics
Location :

Service d'Astrophysique

Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie (LEPCHE)

Saclay

Contact :

Thierry STOLARCZYK

Starting date : 01-09-2017

Contact :

Thierry STOLARCZYK

CEA - DRF/IRFU/SAp/LEPCHE

+33 1 69 08 78 12

Thesis supervisor :

Thierry STOLARCZYK

CEA - DRF/IRFU/SAp/LEPCHE

+33 1 69 08 78 12

More : http://neutrini.free.fr

More : http://irfu.cea.fr/en/Phocea/Vie_des_labos/Ast/ast_technique.php?id_ast=3709

More : http://www.cta-observatory.org/

The CTA observatory is a next-generation ground-based instrument for exploring the sky in gamma rays at very high energies, with a sensitivity ten time better than the existing and an amazing new capacity for the search of transient source counterparts. The goal of the thesis is to participate to the start of the instrument through a contribution to the tuning of the gamma-ray event reconstruction chain, its optimisa-tion for the real time search for transient sources and the analysis of its performance.

Study of Interstellar Grains in the JWST Era

SL-DRF-17-0341

Research field : Astrophysics
Location :

Service d'Astrophysique

Laboratoire d’études de la formation des étoiles et du milieu interstellaire

Saclay

Contact :

Frédéric Galliano

Suzanne MADDEN

Starting date : 01-10-2017

Contact :

Frédéric Galliano

CNRS - DSM/IRFU/SAp/LCEG

01 69 08 18 21

Thesis supervisor :

Suzanne MADDEN

CEA - DSM/IRFU/SAp/LCEG

01 69 08 92 76

Dust grains play a major role in the physics of the interstellar medium. They absorb and reemit in the infrared most of the radiated stellar power. Moreover, they are responsible for the gas heating in photodissociation regions (PDR) and serve as catalysts of numerous chemical reactions. Their properties (chemical composition, size distribution, etc.) are however currently poorly known. These uncertainties put caution on numerous aspects of our knowledge of the interstellar medium: mass estimates, PDR models, unreddening, etc. Refining our comprehension of dust is crucial to understand the life cycle of interstellar matter and its effect on galaxy evolution.



One of the approaches, to tackle these open questions, consists in studying the way the observed grain properties vary with the physical conditions they experience. The PhD thesis we propose is aimed at focussing on the properties of the smallest grains (with a radius smaller than ˜10 nm) and of polycyclic aromatic hydrocarbons (PAH). These interstellar medium components radiates out of equilibrium in the mid-infrared (˜5-40 µm), and are the carriers of numerous resonance bands. This study will focus on several nearby galaxies, including the Magellanic clouds. The interest of studying nearby galaxies rather than the interstellar medium of our own galaxy resides in the diversity of the physical conditions of the environments we can access (metallicity, stellar radiation field intensity, etc.).



Numerous studies have already been published on this subject. However, most of them were superficial. There remains many aspects to study: identifying and physically modeling several bands of solids in star forming regions, and the correlation of the properties of the main PAH bands with the physical conditions diagnosed thanks to the new Herschel data.

The thesis will have several aspects. First, the analysis of mid-infrared spectra, obtained with the satellite Spitzer. Most of these spectra are already reduced. Most of this first step will consist in critically selecting the spectra to study, and homogenizing the data. Then, quantifying the physical components, which is not trivial, will be performed in a sophisticated manner. We propose that the student will develop a hierarchical bayesian model for spectral decomposition, which will allow him a precise quantification of the uncertainties and of the correlations between physical parameters. This new tools and its meticulous application to the data is the guaranty of a precise and original interpretation of the physical processes in the studied regions.



This thematics is particularly relevant for planning the scientific objectives of the James Webb Space Telescope (JWST), which should be launched in 2018.

Weak gravitational lensing: measurement of galaxy shapes to test gravity on cosmological scales

SL-DRF-17-0152

Research field : Astrophysics
Location :

Service d'Astrophysique

Laboratoire CosmoStat (LCS)

Saclay

Contact :

Martin Kilbinger

Starting date : 01-10-2017

Contact :

Martin Kilbinger

CEA - DRF/Irfu/SAp/LCS

01 69 08 17 53

Thesis supervisor :

Martin Kilbinger

CEA - DRF/Irfu/SAp/LCS

01 69 08 17 53

Weak gravitational lensing is the distortion of images of high-redshift galaxies due to structures of the cosmic web on very large scales. It is one of the most promising cosmological probes to study the dark sector of the universe. To quantify these distortions, we have to accurately measure the shapes of these galaxies. Due to the typically very faint luminosity and small apparent size of these galaxies, this is one of the major challenges of weak gravitational lensing analyses.



This thesis has as goal to analyse wide-field optical data, and to measure shapes of background galaxies to create maps of the dark matter distribution. These maps will then be cross-correlated with density maps of foreground galaxies from spectroscopic surveys. These cross-correlations will allow us to distinguish between General Relativity and theories of modified gravity.



The PhD student will use state-of-the-art techniques for imaging processing and advanced statistical tools. This work will serve as milestone for the European space mission Euclid. It will contribute to the preparation of this ultimate cosmological experiment

and help to advance our understanding of the laws in the universe.

Spectral component separation in supernova remnants

SL-DRF-17-0138

Research field : Astrophysics
Location :

Service d'Astrophysique

Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie (LEPCHE)

Saclay

Contact :

Fabio Acero

Starting date : 01-10-2017

Contact :

Fabio Acero

CEA - DSM/IRFU/SAp/LEPCHE

0169084705

Thesis supervisor :

Fabio Acero

CEA - DSM/IRFU/SAp/LEPCHE

0169084705

More : irfu.cea.fr/Sap

More : www.github.com/facero/sujets2017

The main goal of this project is to adapt blind source separation algorithms that have been developed in our laboratory to study the CMB with Planck to X-ray data. Those methods will be used to map the different spectral components that are entangled in supernova remnants (emission lines, thermal continuum and synchrotron). The spatial distribution of those spectral components will allow us to constrain the supernova explosion mechanism, to understand the gas heating at the shock, and how particle are accelerated. Those tools will provide a new way to analyze X-ray data by fully exploiting the spectral and spatial information contained in the data cube instead of processing them separately as it currently the case. This method can be applied in a more general context to any telescope with spectro-imaging capacities and potentially to other fields in physics.

Neutrinos and dark matter under the gaze of quasars

SL-DRF-17-0004

Research field : Astrophysics
Location :

Service de Physique des Particules (SPP)

Groupe Bao

Saclay

Contact :

Nathalie Palanque-Delabrouille

Frédéric BOURNAUD

Starting date : 01-10-2017

Contact :

Nathalie Palanque-Delabrouille

CEA - DRF/IRFU/SPP/Bao

0169083962

Thesis supervisor :

Frédéric BOURNAUD

CEA - DRF/IRFU/SAp/LCEG

01 69 08 55 08

Thanks to observations of the cosmic microwave background and of the way galaxies clusters in the Universe, cosmology has now entered an era of high precision. The Lambda-CDM model has been confirmed as a valid description of cosmological data on the largest scales. Yet, some issues remain unresolved, like the nature of dark matter or the precise role of neutrinos in cosmology. The objective of this thesis is to address these issues both on experimental and theoretical fronts, taking advantage of the information embedded in the Lyman-alpha forest. On the one hand, the student will analyze the largest set of quasar spectra available to date (BOSS & eBOSS experiments, VLT data) to extract key information on the Lyman-alpha forest. On the other hand, he will study, using state-of-the-art hydrodynamical simulations, baryonic processes on galactic scales, and determine their impact on the distribution of gaz on intergalactic scales. Comparing data with the predictions of the simulations, the student will then focus on the cosmological interpretation, shedding new light on neutrinos and dark matter particles (sterile neutrinos or axions).

Evolution of the internal and surface dynamics through asteroseismology

SL-DRF-17-0373

Research field : Astrophysics
Location :

Service d'Astrophysique

Laboratoire Dynamique des Etoiles et de leur Environnement (LDEE)

Saclay

Contact :

Rafael A. Garcia

Starting date : 01-10-2017

Contact :

Rafael A. Garcia

CEA - DSM/IRFU/SAp/LDEE

0169082725

Thesis supervisor :

Rafael A. Garcia

CEA - DSM/IRFU/SAp/LDEE

0169082725

More : http://irfu.cea.fr/Sap/LDEE/index.php

The objective of these PhD is to progress in the understanding of the dynamical processes at work inside stars (mainly red giants) and hence to improve the structure and evolutionary models. The outcome will be a better determination of the stellar ages, which are crucial for stellar physics, the study of planetary systems, and the galactic physics (and galactic archeology). This PhD will have a large impact on the observations made with the NASA Kepler/K2 mission as well as for the NASA/TESS mission (to be launch at the end of 2017), as well as for the ESA/GAIA mission for which the age estimation are being calibrated using asteroseismology. This PhD will also allow to help the preparation of the ESA/M3 PLATO mission for which the CEA (DRF/IRFU/SAp) is deeply involved in both the hardware and the preparation of the scientific tools.

The evolution of black holes/microquasars during outbursts: a spectro-temporal approach

SL-DRF-17-0014

Research field : Astrophysics
Location :

Service d'Astrophysique

Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie (LEPCHE)

Saclay

Contact :

Jérôme RODRIGUEZ

Starting date :

Contact :

Jérôme RODRIGUEZ

CEA - DRF/IRFU/SAp/LEPCHE

01 69 08 98 08

Thesis supervisor :

Jérôme RODRIGUEZ

CEA - DRF/IRFU/SAp/LEPCHE

01 69 08 98 08

The core of the thesis is the study of accretion-ejection phenomena in microquasars (X-ray binaries with jets) through a spectro-temporal study of the high energy emissions.

The candidate will analyse with a systematic and consistent approach the spectral evolution of sources during their entire outburst, while establishing a "map" of the different kind of variability patterns and their eventual links with the spectral flavours.

Specific attention will be dedicated to the study of quasi-periodic oscillations of all types (0.1-500 Hz) with a view to understanding their physical origin. An original approach consisting of the production and analysis of the spectra of these oscillations will be pursued.



The work can be initiated during a 3-month internship (master level).

The candidate must have a strong background in astrophysics with a Master (French Master 2) level, and basic knowledge of high energy astrophysics

Accretion-ejection coupling in microquasars

SL-DRF-17-0326

Research field : Astrophysics
Location :

Service d'Astrophysique

Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie (LEPCHE)

Saclay

Contact :

Stéphane CORBEL

Starting date : 01-09-2017

Contact :

Stéphane CORBEL

Université Paris 7 - DRF/IRFU/SAP/LEPCHE

01 69 08 45 62

Thesis supervisor :

Stéphane CORBEL

Université Paris 7 - DRF/IRFU/SAP/LEPCHE

01 69 08 45 62

More : http://www.chaos-project.fr/

UNDERSTANDING THE FORMATION OF GALAXIES AT HIGH REDSHIFT WITH THE ATACAMA LARGE MILLIMETER ARRAY (ALMA)

SL-DRF-17-0025

Research field : Astrophysics
Location :

Service d'Astrophysique

Laboratoire de Cosmologie et d'Evolution des Galaxies (LCEG)

Saclay

Contact :

Emanuele DADDI

Starting date : 01-10-2017

Contact :

Emanuele DADDI

CEA - DSM/IRFU/SAp/LCEG

Thesis supervisor :

Emanuele DADDI

CEA - DSM/IRFU/SAp/LCEG

A major question in observational cosmology is understanding the motivation for the strong rise of star formation in galaxies in the distant Universe up to the cosmic peak observed at z~1-3. Answering this question requires observations of molecular and atomic gas emission lines for large numbers of distant galaxies and insights into the physics of their interstellar medium, i.e, the gaseous reservoirs from which stars are made and galaxies form. We have already obtained substantial allocations of observing time with ALMA in Cycle3 and Cycle4 to observe the first large, statistical sample of 100+ galaxies at 1

Constraining the Galileon model of modified gravity with growth rate of structure measurements from the eBOSS spectrograph

SL-DRF-17-0429

Research field : Astrophysics
Location :

Service de Physique des Particules (SPP)

Groupe Bao

Saclay

Contact :

Vanina RUHLMANN-KLEIDER

Starting date : 01-10-2017

Contact :

Vanina RUHLMANN-KLEIDER

CEA - DRF/IRFU/SPP/Bao

01 69 08 61 57

Thesis supervisor :

Vanina RUHLMANN-KLEIDER

CEA - DRF/IRFU/SPP/Bao

01 69 08 61 57

The late acceleration of the Universe expansion, revealed at the end of the 1990s and confirmed since then with more precise cosmological data, remains unexplained. Modifications to General Relativity at large scales offer a promising explanation. The Galileon model is one of the few modified gravity models free from theoretical problems. It agrees with present data at the same level as the cosmological constant model. Among these data, measurements of the growth rate of structures are the most direct way of testing deviations from General Relativity, since gravity governs structure formation in the Universe. This thesis proposes to compare the Galileon model to measurements of the growth rate of structures determined from observations by the eBOSS spectrograph. These observations will provide measurements at redshifts between 0.6 and 2.4, a range almost uncovered until now. eBOSS is one of the 3 programs of SDSS-IV, an international collaboration of several hundreds of physicists, engineers and students from 59 institutes and 11 countries. Observations are taken at the 2.5 m telescope of the Apache Point Observatory in New Mexico. Applicants for this thesis are expected to have a robust formation in cosmology and to be motivated by both data analysis and phenomenology. Very good skills in computing and statistical methods will be an asset.

Measurement of cosmological parameters with the Euclid catalogue of clusters of galaxies

SL-DRF-17-0072

Research field : Astrophysics
Location :

Service de Physique des Particules (SPP)

Groupe Cosmologie Millimétique

Saclay

Contact :

Jean-Baptiste Melin

Starting date : 01-10-2017

Contact :

Jean-Baptiste Melin

CEA - DSM/IRFU/SPP/Cosmo mm

01 69 08 73 80

Thesis supervisor :

Jean-Baptiste Melin

CEA - DSM/IRFU/SPP/Cosmo mm

01 69 08 73 80

Euclid is a satellite mission of the European Space Agency with a launch scheduled in 2020. It is designed to observe weak lensing (WL) and galaxy clustering (baryonic acoustic oscillations BAO and redshift-space distortions RSD) but it is also expected to detect about 100,000 clusters of galaxies (CG) between redshift z=0 and z=2. These clusters will provide measurements of cosmological parameters independently of WL, BAO or RSD.

The Euclid collaboration currently develops cluster extraction tools on simulated data and compares their performances. The goal of this thesis is to design and code the higher-level block of the analysis, which will provide the measurements of the cosmological parameters from the Euclid cluster catalogue. This specific tool is called likelihood.

It is located at the heart of the cluster cosmological analysis. It requires a subtle handling of the completeness of the catalogue (fraction of detected clusters on the sky) and of the link between the quantity observed by Euclid (number of galaxies in each cluster) and the quantity included in theoretical models (the mass). Irfu/SPP has developed an expertise on the likelihood function of the cluster catalogue extracted from the Planck satellite data. The work will consist in building the Euclid cluster likelihood using the Planck expertise. In a first step, the Planck likelihood will be adapted to deal with optical catalogues. Then, in a second step, re-designing the tool will be required to overcome the current limitations. The tool will have to adjust jointly cosmological parameters and cluster physical (nuisance) parameters, which were decoupled in the Planck analysis.

SL-DRF-17-0505

Research field : Astrophysics
Location :

Service d'Astrophysique

Laboratoire de Théorie et de Modélisation

Saclay

Contact :

Matthias GONZALEZ

Starting date :

Contact :

Matthias GONZALEZ

Université Paris Diderot - DSM/IRFU/SAp/LMPA

33 1 69 08 17 79

Thesis supervisor :

Matthias GONZALEZ

Université Paris Diderot - DSM/IRFU/SAp/LMPA

33 1 69 08 17 79

More : http://irfu.cea.fr/Pisp/matthias.gonzalez/

More : http://irfu.cea.fr/Sap/

More : http://irfu.cea.fr/Projets/COAST/

Retour en haut