PhD subjects

17 sujets IRFU

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• Astrophysics

SL-DSM-14-0599

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

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

Saclay

Contact person :

Frédéric BOURNAUD

CEA
DSM/IRFU/SAp/LCEG

Starting date : 01-10-2014

Contact person :

Frédéric BOURNAUD

CEA - DSM/IRFU/SAp/LCEG

01 69 08 55 08

Thesis supervisor :

Frédéric BOURNAUD

CEA - DSM/IRFU/SAp/LCEG

01 69 08 55 08

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

Accretion-ejection coupling in microquasars

SL-DSM-14-0107

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie

Saclay

Contact person :

Jérôme RODRIGUEZ

CEA
DSM/IRFU/SAp/LEPCHE

Starting date : 01-10-2014

Contact person :

Jérôme RODRIGUEZ

CEA - DSM/IRFU/SAp/LEPCHE

01 69 08 98 08

Thesis supervisor :

Stéphane CORBEL

Université Paris 7 - LEPCHE

01 69 08 45 62

X-ray binairies with jets (aka microquasars) are excellent laboratories to probe the physics

in extreme environments. They consist of a "normal" companion star and a compact object

(either a neutron star or a black hole). We have, over the past years, shown that relativistic

jets are able to cary a large amount of the accretion energy. This finding has been made

possible thanks to the broad band study (much beyond the radio domain where they are

predominantly seen) of the emission of jets. Understanding these phenomena necessarily requires

multi-wavelength observations and, therefore, a large panel of tasks to perform.



Accretion is the most efficient energy source of the Universe and is seen in a large variety of celestial sources: from the early stages of star formation to active galactic nuclei. Thanks to their variability on "human" time scale (ie fraction of second to days), microquasars allow us to perform a dynamical study of the accretion-ejection coupling by observations mainly done in the X-ray and radio domains. Given the universality of the accretion-ejection, understanding microquasars, will allow a large panel of celestial objects to be understood.



The goal of the thesis is to systematically study muti-wavelength observations of a sample of microquasars mainly in the X-ray and radio domains. Spectral and temporal aspects will be investigated over the totality of their outburst. The parameters (frequency, températures, ...) will then be compared to the theoretical predictions of the models developed by the collaborators of our team.
Characterizing and modeling multi-scale roughness of natural surfaces in visible light

SL-DSM-14-0291

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

Laboratoire d'étude de la Formation des Etoiles et des Planètes

Saclay

Contact person :

Cécile FERRARI

Université Paris Diderot
IRFU/SAP

Starting date : 01-10-2013

Contact person :

Cécile FERRARI

Université Paris Diderot - IRFU/SAP

33169087829

Thesis supervisor :

Cécile FERRARI

Université Paris Diderot - IRFU/SAP

33169087829

The thermal emisison or scattered light of natural surfaces, terrestrial or planetary, is controlled by its roughness at all scales. Regolith, blocks, fractures, hills, all participate to the scattering function in unkonwn proportions. Analytical models of radiative transfer on such surfaces include roughness but globally. During this thesis, the ability of analytical models to reproduce the scattering of visible light by natural surfaces will be evaluated. Ray tracing simulations using LuxRender on DTMs, either synthetic or natural, will be worked out to study the dependence of the scattering function on the multi-scale rugosity. Models and simulations will be compared to the observed scattering function of real terrains observed by satellites or spacecraft like Pléïades, SPOT, HiRISE or CASSINI or by camera onboard hexacopter drones.
Development of micro CdTe and Micromegas ionisation detectors for X and gamma spatial spectro-imaging.

SL-DSM-14-0264

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

Laboratoire de Détection Spatiale

Saclay

Contact person :

Esther FERRER RIBAS

CEA
DSM/IRFU/SEDI/LDEF

Starting date : 01-08-2013

Contact person :

Esther FERRER RIBAS

CEA - DSM/IRFU/SEDI/LDEF

0169083852

Thesis supervisor :

Olivier Limousin

CEA - DSM/IRFU

0169086294

The measurement of the polarization of X and gamma rays is a powerful tool to discover and characterise the high energy emission mechanisms of celestial sources, adding complementary information to the one given by spectra. There are very little measurements of polarisation at high energy due to lack of adequate instruments. However most of the present proposals for new space missions integrate capabilities of polarimetry measurements. This field is announced by the CNES, the French space agency, as a priority in the domain of Space Science. At CEA we are developing semiconductors and gaseous detectors that are likely to be used together based on the properties of photoelectric absorption and Compton Scattering in the X and gamma domains respectively.

In this thesis, we propose to optimise the definition of a novel micro spectro-imaging polarimeter consisting of two ionisation detectors: CdTe semiconductors and Micromegas allowing the measurement of photon polarization in a large dynamic range from 2 keV to 1 MeV. This work could potentially be placed in the context of the realisation of ultra-compact payload for scientific projects on nano-satellites like the BEEP Mission (Bright Eruptive Event Polarimeter).



Disentangling emission from diffuse gamma-ray sources with HESS and Fermi

SL-DSM-14-0466

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie

Saclay

Contact person :

Karl KOSACK

CEA
DSM/IRFU/SAp/LEPCHE

Starting date : 01-09-2014

Contact person :

Karl KOSACK

CEA - DSM/IRFU/SAp/LEPCHE

+33169082020

Thesis supervisor :

Karl KOSACK

CEA - DSM/IRFU/SAp/LEPCHE

+33169082020

More : http://irfu.cea.fr/Pisp/karl.kosack/

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

More : http://www.hess-experiment.eu

The HESS Cherenkov telescope array has been enormously successful in revealing the highest-energy phenomena in the universe through observations of very-high-energy (VHE) gamma rays from 100 GeV to 100 TeV. A particularly strong point of HESS has been its ability to make a survey of the galactic plane, in which a wide variety of gamma-ray sources have been detected. Deeper observations in the plane have revealed multiple regions where the emission is highly complex, with overlapping components from pulsar wind nebulae, supernova remnants, diffuse emission, point-sources, and as-yet unidentified extended sources. Many are also associated with MeV--GeV emission detected by the Fermi satellite. This thesis will focus on the study of extended gamma-ray emission, particularly in supernova remnants and molecular clouds, and building a better multi-wavelength picture of these sources. The student will develop techniques for the modeling and spectral extraction of these sources, which will be a first for Cherenkov Telescope data. Disentangling the components of this gamma-ray emission will provide a unique understanding of particle acceleration processes in the Galaxy
Dune morphogenesis in landscape-scale experiments and link with planetary climate

SL-DSM-14-0902

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

Laboratoire Anneaux et Dynamique des systèmes Planétaires (LADP)

Saclay

Contact person :

Sébastien Rodriguez

Université Paris Diderot
DSM/IRFU/SAp/LADP

Starting date : 01-10-2014

Contact person :

Sébastien Rodriguez

Université Paris Diderot - DSM/IRFU/SAp/LADP

0169088056

Thesis supervisor :

-

During the last two years, new collaborations have been established with the Chinese Academy of Science to develop field experiments on the physics of sand dunes within their natural environment using controlled initial and boundary conditions. This so-called landscape-scale experiment is a novel and unique concept that is particularly well-suited for validation and quantification purposes. Given the extreme conditions encountered in arid deserts and the time scales associated with the development of bedforms, in-situ experiments on aeolian sand dunes have to combine logistics facilities with long term measurements. By successfully meeting these challenges in China, thanks to the local climate and the field expertise of Chinese scientists, we will be able to obtain new experimental evidences for the formation of dunes and their alignment in multimodal wind regimes. To take into account the cumulative effect of seasonal winds, this fieldwork needs to be extended over several years (up to 2017 at least) and will provide a huge amount of data. Hence, the main objective of the Ph.D. thesis will be to continue the landscape-scale experiment from fall 2014 to spring 2017, carrying out the field measurements and all the statistical data analysis. Thus, we will assemble a unique set of data to investigate hydrodynamic and transport properties which are intended to be put in close relation to dune morphodynamics and climate on Earth and other planetary bodies were dunes have been observed (Mars and Saturn largest moon Titan). This comparison may also be done with the help of numerical and laboratory experiments available within our collaboration perimeter.



How do circumstellar disks form ? Characterizing the physical and chemical structure of the youngest protostars at high angular resolution

SL-DSM-14-1019

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

Laboratoire d'étude de la Formation des Etoiles et des Planètes

Saclay

Contact person :

Anaëlle MAURY

CEA
DSM/IRFU/SAp/LFEMI

Starting date : 01-09-2014

Contact person :

Anaëlle MAURY

CEA - DSM/IRFU/SAp/LFEMI

0169089570

Thesis supervisor :

Philippe ANDRÉ

CEA - DSM/IRFU/SAp/LFEMI

0169089265

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

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

One of the main challenges to the formation of stars is the ?angular momentum problem?: the gas contained in a typical star-forming core must reduce its specific angular momentum by 5 to 10 orders of magnitude to form a typical star such as our Sun, or else centrifugal forces will soon balance gravity and prevent inflow, accretion and the growth of the protostellar embryo (Bodenheimer, 1995).

Early analytical analysis (Terebey et al. 1984, Shu, Adams, & Lizano, 1987) proposed that the formation of large (r > 100 AU) centrifugally supported disks in the protostellar cores would allow to transfer angular momentum outward and therefore solve the angular momentum problem.

Indeed, protoplanetary disks with radii 50-200 AU are routinely observed around young T-Tauri stars, however we still don?t know how the progenitors of these disks are formed during the earliest phases of protostellar formation. In fact, not much is known on the structure of circumstellar envelopes surrounding the youngest (Class 0) protostars at the small scales, due to a lack of observations of Class 0 objects at resolutions probing

the <100 AU scales (1'' resolution or better) in the (sub-)millimeter domain where they emit most of their energy.

Characterizing the chemical and physical structure of the inner regions of the youngest protostellar envelopes is crucial to solve the angular momentum problem, and ultimately constrain the formation and evolution models of solar-type stars (origin of the stellar initial mass function, formation of the multiple stellar systems, disks and planets).

In order to tackle this issue, we obtained a large observing program with the Plateau de Bure interferometer (PdBI) and the IRAM 30m telescope. This large program, named CALYPSO (Continuum and Line in Young Protostellar Objects, PI Philippe André), consists in observing the line and continuum emission from an unprecedentedly large sample of 17 very young (Class 0) protostars at high spatial resolutions (0.5'' i.e. 50-100 AU).

The main objective of the proposed thesis project is to characterize the physical and chemical structure of protostellar envelopes on the small scales where disks are observed in more evolved YSOs, therefore testing if the formation of disks is indeed an outcome of, and solution to, the angular momentum problem for star formation.

The PhD student will analyze and interpret high-angular resolution millimeter observations of Class 0 protostars obtained with the PdBI as part of the CALYPSO program, in close collaboration with the CALYPSO working group interested in disk formation questions (Philippe André, Anaëlle Maury, Sébastien Maret, Leonardo Testi and Patrick Hennebelle). He/she will also propose follow-up observations with the NOEMA and ALMA observatories. Moreover, the student will contribute in comparing these observations with the predictions of numerical models for protostellar formation and evolution, in close collaboration with the Chemodyn(Sébastien Maret, Sibylle Anderl, Benoit Commerçon) team.
Measurement of cosmological neutrinos mass with eBOSS

SL-DSM-14-1015

Research field : Astrophysics

Location :

Service de Physique des Particules (SPP)

Groupe Bao

Saclay

Contact person :

Christophe YECHE

CEA
DSM/IRFU/SPP/Bao

Starting date : 01-10-2014

Contact person :

Christophe YECHE

CEA - DSM/IRFU/SPP/Bao

01-69-08-70-50

Thesis supervisor :

Nathalie PALANQUE-DELABROUILLE

CEA - DSM/IRFU/SPP/Bao

01-69-08-39-62

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

During the last decade, the unexpected discovery that neutrinos have non-zero masses attracted the attention of much of the scientific community. However, their mass is still unknown because current observations can only determine mass differences. We know that the sum of the masses is at least 0.06 eV. On an astrophysical standpoint, this small mass is already sufficient to have a significant impact on the formation of structures in our universe, from the smallest (distribution of atomic hydrogen in the intergalactic medium) to the largest (galaxies and clusters of galaxies).

These small scales, of the order of a few Mpc, are accessible through measurements of the Lyman-alpha forest (absorption by the Lyman-alpha line of neutral hydrogen present in the intergalactic medium) that can be observed in the spectra of distant quasars at redshifts z > 2.2. These scales are those where the impact of massive neutrinos on structure formation is the most visible, hence their interest for the determination of the mass of cosmological neutrinos.

Our group is involved in the extension of BOSS: the eBOSS project. As part of SDSS-IV, eBOSS will begin its observations with the Sloan telescope in September 2014. At the end of the project, BOSS and eBOSS together will have observed more than 200,000 quasars with redshifts > 2.2, which will establish a measurement of the neutrino mass with an accuracy better than 0.1eV.
Multichannel Compressed Sensing and its Application in Cosmology with LOFAR and SKA

SL-DSM-14-0147

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

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

Saclay

Contact person :

Jean-Luc STARCK

CEA
DSM/IRFU/SAp/LCEG

Starting date : 01-10-2014

Contact person :

Jean-Luc STARCK

CEA - DSM/IRFU/SAp/LCEG

01 69 08 57 64

Thesis supervisor :

Jean-Luc STARCK

CEA - DSM/IRFU/SAp/LCEG

01 69 08 57 64

More : http://jstarck.free.fr

More : http://www.cosmostat.org/:

The new generation of radio interferometer instruments will allow us to build radio-images with very high resolution quality and high sensitivity. One of the major problem in radio-astronomy imaging is that spatial informations are not fully available, since only a few Fourier components (i.e. the visibilities directly measured by the telescope) can be acquired by a radio-interferometry instrument. Recent developments in harmonic analysis and optimization fields, such as compressed sensing methodology, sparse recovery, and proximal theory for the minimisation of functionals, are typical mathematical tools that have been developed recently and have shown to be very efficient for reconstructing images from few visibilities measurements. Recent developments in harmonic analysis and optimization fields, such as compressed sensing methodology, sparse recovery, and proximal theory for the minimisation of functionals, are typical mathematical tools that have been developed recently and have shown to be very efficient for reconstructing images from few visibilities measurements. These tools presents however serious limitations because they consider only mono-canal data set. The first goal of this thesis is to build a multichannel-Compressed Sensing (MCS) data reconstruction, using both the Compressed Sensing concept and advanced component separation techniques that were developed in the framework of the Planck project. This new tool will open a new way to analyze radio-interferometry data set. Two cosmological applications will be studied:

- Epoch of Reionization (EoR): Our Universe emerged from the "Dark Ages" and began to be reionized 400 million years after the Big Bang, This Epoch of Reionization (EoR) will be observed for the first time with the new generation of radio telescopes such MWA (Australia), the precursor instruments of the major international SKA facility to be developed around 2020. The accurate and precise removal of 21-cm foregrounds from Epoch of Reionization redshifted 21-cm emission data is essential if we are to gain insight into an unexplored cosmological era. This requires that foregrounds must be accurately and precisely removed from the observed data as any error at this stage has the ability to strongly affect the EoR 21-cm signal. Based on MCS, a new foreground removal method will be developed in order to extract the 21cm reionization signal. 1D, 2D and 3D spectra can then be estimated and compared to theoretical prediction

- Weak Lensing: weak lensing (WL) in the radio is a new field, which has been investigated via theory and simulations, but has not yet been implemented in a wide survey. LOFAR and SKA could achieve the first ever cosmological WL survey in the radio. MCS will also allows us to measure shapes of galaxies with a much better accuracy than traditional methods. Then shear power spectra will be derived from the reconstructed shear map in order to constraint the Dark Energy equation of state.
Nature, formation and evolution of compact binaries

SL-DSM-14-0155

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie

Saclay

Contact person :

Sylvain CHATY

Université Paris Diderot et Institut Universitaire de France
LEPCHE/Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie

Starting date : 01-10-2014

Contact person :

Sylvain CHATY

Université Paris Diderot et Institut Universitaire de France - LEPCHE/Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie

01 69 08 43 85

Thesis supervisor :

Sylvain CHATY

Université Paris Diderot et Institut Universitaire de France - LEPCHE/Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie

01 69 08 43 85

More : http://www.aim.univ-paris7.fr/CHATY/chaty/Bienvenue.html

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

Compact binaries, constituted of a compact object (neutron star or black hole) orbiting a so-called "companion star", are among the most fascinating celestial objects of our Universe. The compact object attracts matter from the companion star, this matter accumulates, and is accreted, heated to temperatures of several million degrees, mainly emitting in the X-ray/gamma-ray domain. These objects can be extremely variable, their flux varying by several orders of magnitude at all wavelengths, on time scales ranging from days to months. Thus, to understand the physical mechanisms occurring in these objects, it is necessary to undertake a multi-wavelength study, by observing these objects as soon as an outburst of activity is detected.



The proposed PhD thesis consists in the study of all the physical processes occurring inside compact binaries, governing their formation, evolution, up to their final stage.

The three fundamental pilars of study of these celestial objects, namely their formation and impact on their environment, evolution, and ultimate fate of compact binaries, will be studied during this PhD-Thesis from observations (already obtained, mainly coming from the Herschel satellite and VLT instruments, such as X-shooter and ISAAC, or to be obtained, from VLT-I and ALMA for instance) and models (population synthesis of compact binaries).

This PhD thesis, covering many fields of Astrophysics, from stellar formation, via stellar evolution, to the most energetic events in our Universe, will allow us to get a better understanding of these extraordinary laboratories of high energy physics in our Universe: the compact binaries.
Physical and statistical modelling of interstellar dust properties in the nearby universe

SL-DSM-14-0393

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

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

Saclay

Contact person :

Frederic Galliano

CNRS
DSM/IRFU/SAp/LCEG

Starting date : 01-10-2014

Contact person :

Frederic 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.

Probing the formation and evolution of protostellar cores within interstellar filaments: Kinematics from millimeter-line observations and comparison with numerical simulations

SL-DSM-14-1018

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

Laboratoire d'étude de la Formation des Etoiles et des Planètes

Saclay

Contact person :

Philippe ANDRE

CEA
DSM/IRFU/SAp/LFEMI

Starting date : 01-09-2014

Contact person :

Philippe ANDRE

CEA - DSM/IRFU/SAp/LFEMI

0169089265

Thesis supervisor :

Philippe ANDRÉ

CEA - DSM/IRFU/SAp/LFEMI

0169089265

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

More : http://www.herschel.fr/cea/gouldbelt/en/

Recent studies of nearby molecular clouds with the Herschel Space Observatory have revolutionized our understanding of the link between the structure of the interstellar medium (ISM) and the early phases of the star formation process. The Herschel results favor a scenario in which interstellar filaments and prestellar cores represent two key steps: first turbulence stirs up the gas, giving rise to a universal web-like structure in the ISM, then gravity takes over and controls the further fragemntation of filaments into prestellar cores and ultimately protostars.

However, the Herschel results do not provide direct constraints on the dynamics of star-forming clouds. As a result, many important issues remain open. For instance, it is not known whether most prestellar cores decouple from their parent filament when they collapse to protostars or, on the contrary, accrete a significant amount of mass from the background filament while collapsing. The goal of the proposed PhD thesis is to address this problem by confronting follow-up spectral line observations of the Herschel filaments/cores with numerical simulations of cloud collapse and fragmentation.
Star formation and galaxy evolution during the crucial first 3 Gyr of cosmic history

SL-DSM-14-0450

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

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

Saclay

Contact person :

Emanuele DADDI

CEA
LCEG/Laboratoire de Cosmologie et d'Evolution des Galaxies

Starting date : 01-09-2013

Contact person :

Emanuele DADDI

CEA - LCEG/Laboratoire de Cosmologie et d'Evolution des Galaxies

Thesis supervisor :

Emanuele DADDI

CEA - LCEG/Laboratoire de Cosmologie et d'Evolution des Galaxies

Recent observational advances have demonstrated that the distribution of star formation in galaxies through cosmic time is remarkably simple and well behaved, as shown by the existence of tight relation between fundamental galaxy parameters like stellar masses, star formation and molecular hydrogen content. This suggests that the formation and evolution of galaxies is ultimately driven by the availability of fuel gas reservoirs (and not by the physics of interactions) and thus to the accretion of baryons from the intergalactic space onto dark matter halos. This general picture is remarkably well constrained up to redshifts of 2, however we currently don't know

if this still holds at earlier times, corresponding to the crucial first 3 Gyr of comsic time that are generally referred to as the 'early-phases' of galaxy formation and evolution when galaxies and structures were still in their infancy. Exploratory observations have revealed potential conflicts with theorethical predictions in the standard model but substantial observational progress is needed to obtain a clear picture of these phases. The successful candidate will join my research group and participate intense observational efforts to characterize the early phase of star formation in the distant Universe. This will include working with the deepest optical/near-IR data to select distant star forming galaxy candidates, and study their star formation, dust and gas content through direct detection and stacking in the far-IR and submm domains, using the deepest Herschel data which are available to us, publicly available facilities, and proposing for telescope time for crucial missing ingredients. In addition, the candidate will be able to work with deep ground based and space based spectroscopy to study high redshift galaxy emission lines and constrain their star formation histories. The candidate will gain the necessary scientifical and technical expertize to be able to competitively request telescope time with major forthcoming facilities like ALMA and JWST.
Study of Dark Energy in eBOSS survey (SDSS-IV)

SL-DSM-14-0024

Research field : Astrophysics

Location :

Service de Physique des Particules (SPP)

Groupe Bao

Saclay

Contact person :

Nathalie PALANQUE-DELABROUILLE

CEA
DSM/IRFU/SPP/Bao

Starting date : 01-09-2014

Contact person :

Nathalie PALANQUE-DELABROUILLE

CEA - DSM/IRFU/SPP/Bao

01-69-08-39-62

Thesis supervisor :

Christophe YECHE

CEA - DSM/IRFU/SPP/Bao

01-69-08-70-50

More : http://irfu.cea.fr

Acceleration of Universe expansion is one the main topics of modern cosmology. It can stem from a new component, dark energy, which corresponds to 70% of the energy content of Universe. Several probes can be used to study its nature through its state equation. In this thesis, we propose to study it by measuring a standard ruler given by baryonic acoustic oscillation (BAO) frequency for various redshift universe slices. This approach was used successfully for the first time in 2005 by the Sloan Sky Digital Survey (SDSS). This positive observation was confirmed in 2012 by BOSS project (SDSS-III) both with galaxies and HI absorbers in quasar spectra. Irfu/SPP is currently involved in the analysis of BOSS observations.

Irfu/SSP participates to the next generation of experiments studying BAO, eBOSS, within the international collaboration SDSS-IV. One of the eBOSS goals, is to study the quasar cross-correlation with quasar Ly-alpha forest in order to measure BAO scale at a redshift around 2.2. eBOSS will start to perform quasar spectra in September 2014.

First, the graduate will develop statistical methods to select quasars based on SDSS and PTF imaging. Then, he will measure the quasar cross-correlation function in order to extract the BAO scale. Finally, he will interpret his results in terms of cosmological constraints.
Study of the past activity of the supermassive black hole at the Galactic center

SL-DSM-14-0310

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie

Saclay

Contact person :

Andrea GOLDWURM

CEA
DSM/IRFU/SAp/LEPCHE

Starting date : 01-10-2014

Contact person :

Andrea GOLDWURM

CEA - DSM/IRFU/SAp/LEPCHE

0169088669

Thesis supervisor :

Andrea GOLDWURM

CEA - DSM/IRFU/SAp/LEPCHE

0169088669

More : http://irfu.cea.fr/Sap/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=974

We propose to carry out the analysis and interpretation of part of the X-ray data of the deep surveys of the Galactic Center (GC) obtained recently by our group with the XMM-Newton and Chandra satellites, along with the additional data that will be collected in 2014-2015, in order to study several non-thermal sources of the region and in particular those that trace the behaviour of the galactic supermassive black hole (SMBH), Sgr A*. The main goal of the project is to reconstruct and understand the past outburst activity of Sgr A* through the temporal and morphological variations of the X-ray emission of the nearby molecular clouds (MC) which reflect towards us, with a certain delay and specific spectral signatures, the Sgr A* radiation which illuminated them. The student will continue and complete the study of the GC MC X-ray emission that our group has started, including new data and observations at radio and mm wavelengths, in order to derive the Sgr A* light curve over the last few centuries and to explore the processes that may be responsible for this increase of activity (accretion of non-homogenous stellar winds, star tidal disruption events, etc.). The candidate will then compare Sgr A* behaviour with that of SMBH hosted by external inactive galaxies and those powering Active Galactic Nuclei. The work may lead to study other GC non-thermal sources and possibly compare results with first GC measurements of the ASTRO-H X-ray satellite to be launched in 2015.
Study of the physical processes of star formation and the interstellar medium in galaxies

SL-DSM-14-0334

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

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

Saclay

Contact person :

Suzanne MADDEN

CEA
DSM/IRFU/SAp/LCEG

Starting date : 01-10-2014

Contact person :

Suzanne MADDEN

CEA - DSM/IRFU/SAp/LCEG

01 69 08 92 76

Thesis supervisor :

Suzanne MADDEN

CEA - DSM/IRFU/SAp/LCEG

01 69 08 92 76

One of the enduring astrophysical problems we are plagued by today concerns the impact of star formation on the lifecycle of the interstellar medium (ISM) of galaxies. This is a fundamental problem because most of the information we can gather on galaxies, and specifically their star formation activity, metallicity, galaxy mass, nuclear activity, galaxy morphological type, global age of the galaxy and the presence of an interaction or merger is actually obtained through the emission of the ISM.



This thesis project will focus on understanding how star formation shapes the interstellar medium and controls the spectral characteristics of galaxies. To this end, the thesard will develop spectral diagnostics of the stellar interaction with the interstellar medium (MIS) ? the ionized and photo-dissociated gas as well as the dust emission measures ? which can then be widely employed to accurately determine the star formation activities of galaxies. Applied on cosmological scales, these improved and physics-based spectral diagnostics can transform what is today a broad sketch of the evolution of star formation with cosmic time into an accurate description of the evolution of the star formation process itself along the ages of the universe.



At the end of the thesis, the PhD candidate will have acquired a solid expertise in technical treatment of observations and data bases, numerical techniques in data analysis and writing and using numerical codes, the physics of the fundamental processes taking place in galaxies and the overall astrophysical interprétation of nearby galaxies as well as on cosmological scales.

Supernova remnants with Fermi, CTA, and the cosmic ray origin

SL-DSM-14-0419

Research field : Astrophysics

Location :

Service d'Astrophysique (SAp)

Laboratoire d'Etudes des Phénomènes Cosmiques de Haute Energie

Saclay

Contact person :

Jean BALLET

CEA
DSM/IRFU/SAp/LEPCHE

Starting date : 01-09-2014

Contact person :

Jean BALLET

CEA - DSM/IRFU/SAp/LEPCHE

01 69 08 70 17

Thesis supervisor :

Thierry STOLARCZYK

CEA - DSM/IRFU/SAp/LEPCHE

+33 1 69 08 78 12

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

More : http://fermi.gsfc.nasa.gov/ssc/

The goal of the PhD is the study of supernova remnants with gamma rays, trying to pin down the acceleration sites of high energy cosmic rays. The study will be based on observations by the Fermi satellite (covering the energy range 30 MeV-300 GeV) and the ground Cherenkov telescopes (Hess, Magic, Veritas, covering energies from 50 GeV to more than 10 TeV), covering a broad energy range, from 30 MeV to beyond 10 TeV. The results obtained shall contribute to the scientific program of CTA, an observatory in its preparatory phase expected to improve the sensitivity of the current Cherenkov instruments by a factor of ten. Several aspects will be explored:

? Spectral modelling of a few bright supernova remnants detected by Fermi and by Cherenkov telescopes, in the light of radio and X-ray observations;

? Participating in building the Fermi catalogue of supernova remnants at GeV energies;

? Developing a population model for galactic supernova remnants in the GeV-TeV energy range on the basis of theoretical expectations;

? Applying this population model to predict the discovery potential of CTA in a semi-quantitative way, and developing candidate selection criteria for detailed CTA observations.



Keywords: supernova remnants, cosmic rays, gamma rays, Fermi acceleration, Fermi satellite, CTA observatory