PhD subjects

13 sujets IRFU/DAP

Dernière mise à jour : 07-12-2021


• Astrophysics

• Numerical simulation

 

Investigating the nature of Gamma-Ray Bursts using MXT on board the SVOM mission

SL-DRF-22-0413

Location :

Direction d’Astrophysique (DAP)

Laboratoire des spectro-Imageurs spatiaux (LISIS)

Saclay

Contact :

Diego GOTZ

Starting date : 01-10-2022

Contact :

Diego GOTZ
CEA - DRF/IRFU/DAP/LISIS

+33-1-69-08-59-77

Thesis supervisor :

Diego GOTZ
CEA - DRF/IRFU/DAP/LISIS

+33-1-69-08-59-77

Personal web page : https://irfu.cea.fr/Pisp/diego.gotz/

Laboratory link : https://www.svom.eu

Gama-Ray Bursts (GRB) are short (up to few tens of seconds) and intense flashes of gamma-rays, appearing from random directions over the entire sky. The gamma-rays (and the later afterglow emission observed at other wavelenghts) are associated to shock accelerated particles within relativistic narrow jets of plasma. The jets are created by the collapse of very massive stars (more than 50 times the mass of the Sun) or the merging of two compact objects (e.g. two neutron stars).

SVOM (Space based Variable astronomical Object Monitor) is a Sino-French mission developed in collaboration by the French Space Agency (CNES) and the Chinese Academy of Science (CAS) and the Chinese National Space Administration (CNSA). It is planned for launch early 2023 for a nominal mission lifetime of three years.

It will carry on-board four instruments among which the Micro-channel X-ray Telescope (MXT), a focusing X-ray telescope with a field of view of about 1°x1°, sensitive in the 0.2-10 keV energy range. The successful PHD candidate will be part of the MXT science team and be in charge of analyzing MXT data, since the very beginning of the SVOM mission. X-ray afterglow data will be coupled to the multi wavelength data in order to build a clear phenomenological picture of the SVOM GRBs, and to understand GRB progenitors and radiation processes.
Simulating and optimising (sub-)millimetre observations for cosmology and interstellar medium science

SL-DRF-22-0486

Research field : Astrophysics
Location :

Direction d’Astrophysique (DAP)

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

Saclay

Contact :

Marc SAUVAGE

Starting date : 01-09-2021

Contact :

Marc SAUVAGE
CEA - DSM/IRFU/SAp/LFEMI

01 69 08 62 99

Thesis supervisor :

Marc SAUVAGE
CEA - DSM/IRFU/SAp/LFEMI

01 69 08 62 99

Laboratory link : https://irfu.cea.fr/dap/index.php

The wavelength range from millimeter to submillimeter is the preferred domain for the observation of the cold universe (interstellar medium) and the distant universe (microwave cosmological background, first galaxies). Following the success of the Herschel and Planck space missions, future space and ground-based observatories in this wavelength range are under study and are among the priorities of NASA and ESA programs for the coming decades. Scientific objectives range from the study of the primordial universe and the formation of high spectral shift structures to the role of the magnetic field in structuring the interstellar medium and star formation in our own galaxy. The optimization of mission concepts, from the required instrumental performances to the observation and data analysis strategies, requires the realization of simulations of the measurements of these future missions. The objective of the thesis will be to model these measurements and to develop a flexible simulation tool, applicable to different instrument and mission concepts. This tool will be used to inform the preparation of future observing missions in the millimeter and sub-millimeter range. This work will interface with a model of microwave sky emission (developed elsewhere), and with a study of the characteristics and imperfections of detectors developed at DAp for these future missions. A strong interaction with the research groups on the interstellar medium and the cosmic microwave background is also planned in order to understand the instrumental needs of these fields
Measuring the growth of massive structures in the distant Universe with deep multi-wavelength surveys

SL-DRF-22-0311

Research field : Astrophysics
Location :

Direction d’Astrophysique (DAP)

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

Saclay

Contact :

Emanuele DADDI

Starting date : 01-10-2021

Contact :

Emanuele DADDI
CEA - DRF/IRFU/DAP/LCEG


Thesis supervisor :

Emanuele DADDI
CEA - DRF/IRFU/DAP/LCEG


A growing convergence of research lines point to the first massive structures, like groups and clusters, assembling in the distant Universe as rosetta-stones to try to unveil important unsolved questions in galaxy and structures formation and evolution. This includes understanding the physical processes by which galaxies are fuelled by gas (which allows them to form their stars), by which galaxies change their structures, the role played by galaxy mergers, the feedback with their internal growing black holes, and interactions and the paths through which they eventually stop forming stars.



We propose a PhD project in which the student will participate to this research within a large international consortium that is leading large observational program of distant groups and clusters. Primarily the PhD student will be involved in using data from a recently awarded large program with the NOEMA interferometer that will use 159 hours of observations to discovery (confirm) and study 40 groups and clusters at 2


This thesis will potentially provide a solid formation for the student in many aspects of observational cosmology, from observations at one of the best ground-based telescopes to data analysis and interpretation all the way possibly to modeling, based also on the interests of the students and on results.
Intergalactic magnetic field and gamma ray bursts with CTA

SL-DRF-22-0462

Research field : Astrophysics
Location :

Direction d’Astrophysique (DAP)

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

Saclay

Contact :

Renaud Belmont

Thierry STOLARCZYK

Starting date : 01-09-2022

Contact :

Renaud Belmont
Université de Paris (Paris 7) - DRF/IRFU/DAP/LEPCHE


Thesis supervisor :

Thierry STOLARCZYK
CEA - DRF/IRFU/DAp/LEPCHE

+33 1 69 08 78 12

Personal web page : http://irfu.cea.fr/Pisp/thierry.stolarczyk/

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

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

The intergalactic magnetic field pervading the cosmic voids is suspected to be a relic field originating from the very first epoch of the cosmic history. The goal of this PhD is to look for signatures of this field in the high-energy data of gamma-ray bursts, and to predict the ability of the future CTA observatory to constrain its properties. This work combines both theoretical modelling and analysis of simulated CTA data.
Study of accretion and ejection processes in variable black hole systems with SVOM

SL-DRF-22-0487

Research field : Astrophysics
Location :

Direction d’Astrophysique (DAP)

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

Saclay

Contact :

Andrea GOLDWURM

Starting date : 01-10-2022

Contact :

Andrea GOLDWURM
CEA - DRF/IRFU/DAp/LEPCHE

0169088669

Thesis supervisor :

Andrea GOLDWURM
CEA - DRF/IRFU/DAp/LEPCHE

0169088669

Laboratory link : https://irfu.cea.fr/dap/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=974

More : https://apc.u-paris.fr/APC_CS/fr

We propose to carry out a study of accretion and ejection processes in black hole systems which are highly variable or transient emitters of high energy photons, by using the multi-wavelength data of the SVOM space mission and the relevant multi-messenger data that will be available to our laboratory.

The super-massive black holes located in galaxy centers, in particular those that generate the luminous Active Galactic Nuclei (AGN), or the stellar-mass black holes that evolve in bright X-ray close binary systems (XRB), show a high-energy emission (in X and gamma-rays) which is always variable and often transient. They will be priority targets for the Chinese-French space mission SVOM dedicated to the variable high-energy sky and that will be launched early 2023. SVOM will provide a large set of data from optical to gamma-ray wavelengths of high energy sources particularly those located at high galactic latitudes during the observations of the General Program (GP) of the mission. Galactic sources will be pointed instead mainly during Target of Opportunity (ToO) observations triggered by the appearance in the sky of a new transient source, for example of a BH X-ray Nova. APC has important responsibilities in these programs and it will be at the center of the scientific projects that will exploit these data. The thesis will focus on those programs dedicated to analysis and astrophysical interpretation of the mission data on BH systems, and will profit of, and contribute to, the large expertise in X/gamma-ray data analysis and in astrophysics of compact objects of the team. Particular attention will be dedicated to the multi-messenger astronomy context of the BH observations, with the search for possible neutrino, cosmic ray and gravitational wave emissions associated to the studied variable high-energy electromagnetic events.
Cross-correlating Euclid and DESI to probe the dark-matter - baryon connection in the cosmic web using weak gravitational lensing

SL-DRF-22-0483

Research field : Astrophysics
Location :

Direction d’Astrophysique (DAP)

Laboratoire CosmoStat (LCS)

Saclay

Contact :

Martin Kilbinger

Starting date : 01-10-2022

Contact :

Martin Kilbinger
CEA - DRF/IRFU/DAP/LCS

21753

Thesis supervisor :

Martin Kilbinger
CEA - DRF/IRFU/DAP/LCS

21753

Personal web page : http://www.cosmostat.org/people/kilbinger

Laboratory link : http://www.cosmostat.org/

Weak gravitational lensing, the distortion of images of high-redshift galaxies due to foreground matter structures on large scales, is one of the most promising tools of cosmology to map the dark-matter distribution in the Universe. By combining weak lensing observations with foreground galaxy samples, we can measure the connection between dark matter and baryonic mass in galaxies. The lensing - galaxy cross-correlation is one of the main blocks in modern cosmology. It is an ingredient to test a variety of models of modified gravity, in which photons from weak lensing and galaxies experience different gravitational potentials. It further allows to measure two of the most important astrophysical uncertainties in cosmology, the intrinsic alignments of galaxies and galaxy bias.

The goal of this PhD thesis is to measure cross-correlations between weak lensing and galaxies, using the upcoming Euclid and DESI surveys. In preparation, existing weak-lensing data will be used from UNIONS, an ongoing imaging survey covering 3,600 square degree to date. This data will be cross-correlated with existing BOSS/eBOSS spectroscopic galaxies. This work aims toward a better understanding of the dark-matter – baryon connection, which will not only help to improve cosmological analyses, but also deepen our knowledge of how galaxies formed in their dark-matter environments in the early Universe.

Understanding the evolution of galaxies with the James Webb Space Telescope

SL-DRF-22-0365

Research field : Astrophysics
Location :

Direction d’Astrophysique (DAP)

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

Saclay

Contact :

Benjamin MAGNELLI

David ELBAZ

Starting date : 01-09-2022

Contact :

Benjamin MAGNELLI
CEA - DRF/IRFU

0169086825

Thesis supervisor :

David ELBAZ
CEA - DRF/IRFU

0169085439

The James Webb Space Telescope (JWST) will revolutionize our understanding of the evolution of galaxies in the so-called "cosmic noon" era. With its unparalleled angular resolution in the near- and mid-infrared window, it will measure the distributions of stars and dust-obscured star formation on the kpc scale, and reveal the presence of active dust-obscured supermassive black holes at their centers.

In the scenario so far favored to explain the evolution of galaxies and, in particular, the morphological transformation of spirals into ellipticals, it is the mergers of galaxies that destroy the disks and generate the spheroids. However, recent observations by our team have revealed the presence of compact star-forming nuclei in distant galaxies, supporting an alternative scenario in which they were built in situ, slowly and not abruptly.

This thesis will aim to distinguish these two scenarios of galaxy formation and morphological transformation by combining JWST/PRIMER/NIRCam images with HST/CANDELS/ACS images. Our team will have access to two major JWST cosmological programs, CEERS (PI. S.Finkelstein) and PRIMER (PI. J.Dunlop) whose data should arrive as early as June 2022 (or at the latest Dec.2022). We will perform a spatially resolved analysis of the spectral energy distribution of about 1200 galaxies which will allow, in particular, to determine their distribution of stars and star formation, decisive information to understand their origin and evolution.
Characterization of magnetic activity cycles of the Sun a solar-like stars with data from SoHO, Kepler, and TESS satellites

SL-DRF-22-0376

Research field : Astrophysics
Location :

Direction d’Astrophysique (DAP)

Laboratoire de dynamique des étoiles des (Exo) planètes et de leur environnement (LDE3)

Saclay

Contact :

Rafael A. Garcia

Starting date : 01-10-2022

Contact :

Rafael A. Garcia
CEA - DRF/IRFU/DAP/LDE3

0169082725

Thesis supervisor :

Rafael A. Garcia
CEA - DRF/IRFU/DAP/LDE3

0169082725

Laboratory link : https://irfu.cea.fr/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=971

The objective of this PhD is to better understand the magnetic activity of the solar-like stars using as a reference our Sun. These stars have and external convective envelope. The interaction of the convection, rotation and magnetic fields generate dynamo process that are at the origin of dynamos which generates magnetic activity cycles. Understanding this magnetic activity and the associated cycles is of the main importance to better understand the development of life as the one on Earth as well as to improve the detectability of exoplanets orbiting these active stars.
Impact of rotation and magnetism on the excitation of stellar oscillations: predictions for space asteroseismology

SL-DRF-22-0382

Research field : Astrophysics
Location :

Direction d’Astrophysique (DAP)

Laboratoire de dynamique des étoiles des (Exo) planètes et de leur environnement (LDE3)

Saclay

Contact :

Stéphane MATHIS

Starting date : 01-09-2022

Contact :

Stéphane MATHIS
CEA - DRF/IRFU

0169084930

Thesis supervisor :

Stéphane MATHIS
CEA - DRF/IRFU

0169084930

Laboratory link : http://irfu.cea.fr/Sap/LDEE/index.php

From galactic to planetary systems’ scales, stars are the elementary building blocks of our Universe. Their nucleosynthesis et their magneto-rotational dynamics drive their evolution and those of their environment. The unique observational method to probe their internal structure, rotation, and potentially magnetism is asteroseismology. Asteroseismology is the branch of astrophysics that studies the oscillations of stars. During the last decade, asteroseismology has revolutionised our understanding of the evolution, internal mixing, and rotation of stars and the characterisation of their planets. To be able to take advantage of all the power of asteroseismology it is mandatory to understand the excitation mechanisms (and the damping) of stellar oscillations. This is the key objective of this PhD project where we will study their stochastic excitation by turbulent stellar convective regions. The innovative aspect will be to take simultaneously the action of rotation and magnetism on the propagation of stellar oscillations and on the convective source that trigger them into account. This theoretical project is part of the scientific preparation of the M3 ESA space mission, which will be launched in 2026 in which CEA is highly involved.
New insights into radiative transfer modelling of exoplanet atmospheres

SL-DRF-22-0386

Research field : Astrophysics
Location :

Direction d’Astrophysique (DAP)

Laboratoire de dynamique des étoiles des (Exo) planètes et de leur environnement (LDE3)

Saclay

Contact :

Antonio Garcia Muñoz

Starting date :

Contact :

Antonio Garcia Muñoz
CEA - DRF


Thesis supervisor :

Antonio Garcia Muñoz
CEA - DRF


Personal web page : http://antoniogarciamunoz.wordpress.com/

Laboratory link : https://irfu.cea.fr/dap/LDEE/index.php

More : https://irfu.cea.fr/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=971

With ~5,000 exoplanets known (http://exoplanet.eu), it is clear that the observed diversity of exoplanets is linked to their histories. In this setting, exoplanet science is faced with two key questions. The first one is how evolution may have modified the planets’ bulk compositions. The question is timely as various facilities (JWST, launch date: December 2021; ARIEL, launch in 2028; E-ELT: first light in 2027) will study in unprecedented detail the atmospheres of exoplanets with spectroscopy. The second question is how evolution may have shaped the demographics of exoplanets. Notably, our grasp of demographics has changed radically in the last decade, and will continue evolving thanks to new discoveries from photometric space missions (e.g. TESS, PLATO) and radial velocity surveys on the main ground-based telescopes.

Digesting that empirical knowledge requires physically-motivated models that connect the properties of the planets and their host stars throughout their shared histories. To that end, our project will build a sophisticated treatment of radiative transfer (RT) for close-in exoplanets with both hydrogen- and non-hydrogen-dominated atmospheres. The RT modules will be implemented into the team’s photochemical-hydrodynamic models to better understand the temporal evolution of the exoplanets. The predictions will help interpret the constraints that JWST will set on the composition of a few small exoplanets for which observing time has been granted as part of GTO+GO programs.

SL-DRF-22-0140

Research field : Astrophysics
Location :

Direction d’Astrophysique (DAP)

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

Saclay

Contact :

Jérôme RODRIGUEZ

Starting date : 01-10-2022

Contact :

Jérôme RODRIGUEZ
CEA - DRF/IRFU/DAp/LEPCHE

01 69 08 98 08

Thesis supervisor :

Jérôme RODRIGUEZ
CEA - DRF/IRFU/DAp/LEPCHE

01 69 08 98 08

Laboratory link : https://irfu.cea.fr/dap/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=974

Cosmology from LiteBIRD and synergy with large-scale surveys like Euclid

SL-DRF-22-0485

Research field : Astrophysics
Location :

Direction d’Astrophysique (DAP)

Laboratoire CosmoStat (LCS)

Saclay

Contact :

Valeria Pettorino

Starting date : 01-10-2022

Contact :

Valeria Pettorino
CEA - DRF/IRFU/DAP/LCS


Thesis supervisor :

Valeria Pettorino
CEA - DRF/IRFU/DAP/LCS


Personal web page : https://www.cosmostat.org/people/valeria-pettorino

Laboratory link : https://www.cosmostat.org

More : https://www.valeriapettorino.com/

This PhD proposal is meant to combine information from galaxy surveys like the forthcoming Euclid space mission and Cosmic Microwave Background Experiments from ground and space.

The Cosmic Microwave Background radiation has demonstrated to be a powerful probe for cosmology: its temperature anisotropies carry information on the early-time Universe, as well as on the structure encountered along the light path. Measurements from balloons and detectors from ground are contributing to detail this picture with current data from Planck space mission, and forthcoming data from ground, balloons, and space.

Within galaxy surveys, ESA Euclid satellite , to be launched in 2023, will observe how galaxies formed to study the nature of dark energy and dark matter.

The PhD project is co-supervised by Valeria Pettorino (CEA/DRF/IRFU/DAp/LCS) and Dr. Stéphane Ilic (IJLAB, Orsay). We have identified three main goals:

1. contribute to the estimation of the scientific impact of LiteBIRD CMB space mission via forecasts;

2. contribute to the synergy between CMB experiments and Euclid within the Euclid likelihood development;

3. investigate different methods to separate foreground components and improve the reconstruction of the CMB signal.

Likelihood-free cosmological parameter inference using theoretical high-order statistics predictions

SL-DRF-22-0405

Research field : Numerical simulation
Location :

Direction d’Astrophysique (DAP)

Laboratoire CosmoStat (LCS)

Saclay

Contact :

Jean-Luc STARCK

Starting date : 01-10-2022

Contact :

Jean-Luc STARCK
CEA - DSM/IRFU/SAp/LCS

01 69 08 57 64

Thesis supervisor :

Jean-Luc STARCK
CEA - DSM/IRFU/SAp/LCS

01 69 08 57 64

Personal web page : http://jstarck.cosmostat.org

Laboratory link : http://www.cosmostat.org

The Euclid satellite, to be launched in 2023, will observe the sky in the optical and infrared, and will be able to map large scale structures and weak lensing distortions out to high redshifts. Weak gravitational lensing is thought to be one of the most promising tools of cosmology to constrain models. Weak lensing probes the evolution of dark-matter structures and can help distinguish between dark energy and models of modified gravity. Cosmological parameters are traditionally estimated using a Gaussian likelihood based on theoretical predictions of second order statistic such as the power spectrum or the two point correlation functions. This requires to build a covariance matrices, and therefore need a lot of very heavy n-body simulations. This approach presents also several additional drawbacks: First, second order statistics captures all available information in the data only in the case of Gaussian Random Fields, while matter distribution is highly non-Gaussian showing many features such filaments, walls or clusters. Second, the covariance matrix is cosmology dependent and the noise it generally not Gaussian, both aspects being generally poorly taken into account. Finally, all systematic effects such as masks, intrinsic alignement, baryonic feedback are very difficult to take into account. For all these reasons, a new approach has recently emerged, called likelihood-free cosmological parameter inference which are based on a forward modelling. It has the great advantage to not need covariance matrices anymore, avoiding the storage of huge simulated data set (we typically need 10000 n-body realisations for each set of cosmological parameters). Furthermore, it opens us the door to use high order statistical information and it is relatively straightforward to include all systematics effect. It has however two serious drawbacks, the firsts one is the need of huge GPU ressources to process surveys such as Euclid and the second is that the solution relies on the accuracy of simulations, which could lead to infinite discussion in case the results are different from what is expected. Thanks to a recent breakthrough (Codis, 2021), we have now theoretical tools to predict, for a given set of cosmological parameters, the multi-scale density probability function (pdf) of convergence maps such as the one that will be observed with Euclid.

The goal of this PhD work is to develop an hybrid approach, consisting in a likelihood-free cosmological parameter inference which would be based on the high order statics theoretical prediction rather than n-body simulations. It would therefore have the advantage of both previously described approaches, as it will not need to store huge data set to compute a covariance matrix and it will not require huge CPU/GPU ressources as the forward modelling method. This intense frugality will make this approach highly competitive to constraint the cosmological model using high order statistics in future surveys.

To achieve this goal, the first step will be to build a map emulator, similar to what has been done for 2 point statistics (i.e. the flask method), but which respects accurately the high order predictions. Using this emulator, it will then be possible to use it as a bypass in a recently developed Likelihood Free Inference code. This will allow the use of high order statics such as the l1-norm of the wavelet transform of the convergence to constrain the cosmological parameters, which is an extremely powerful summary statistic (Ajani et al, 2021). The developed method will be used first on the CFIS survey and then on Euclid.



References

Barthelemy A., Codis S. and Bernardeau F., "Probability distribution function of the aperture mass field with large deviation theory", 2021, MNRAS, 503, 5204;

V. Ajani, J.-L. Starck and V. Pettorino, "Starlet l1-norm for weak lensing cosmology", Astronomy and Astrophysics,  645, L11, 2021.

 

Retour en haut