Assemblage des galaxies au cours du temps. Evolution chimique des galaxies à 1<z<2 avec la spectroscopie 3D

L'étude de l'assemblage de la masse des galaxies au cours du temps est un sujet important dans le contexte de la formation et de l'évolution des galaxies. Aujourd'hui, plusieurs grands projets tentent de comprendre quels sont les processus à l'origine de l'évolution des galaxies grâce à l'utilisation de la technique de la spectroscopie 3D qui permet d'accéder en détails aux propriétés physiques des galaxies à différentes époques de l'Univers. Grâce aux raies d'émission, c'est la physique du milieu interstellaire des galaxies à grand redshift qui est étudiée. Ainsi on a pu jusqu'à présent s'intéresser majoritairement à la cinématique de ces objets lointains et découvrir des disques en rotation jusqu'à des redshifts élevés (z<3). Dans le cadre du projet MASSIV dirigé par T. Contini, on étudie ici la métallicité du gaz interstellaire des galaxie à 1<z<2, avec le spectrographe 3D SINFONI au VLT. Pour déterminer cette quantité on utilise le rapport de flux dans les raies adjacentes de l'azote (NII6584) et de l'hydrogène (Halpha), et un indicateur reliant cette quantité à l'abondance d'oxygène. Avec les cubes de données issus de la réduction, à laquelle j'ai consacré une importante partie de mon travail, j'ai pu étudier la métallicité intégrée des galaxies du premier échantillon MASSIV ainsi que d'un échantillon de 9 galaxies d'une session d'observations visant à prouver la faisabilité du projet MASSIV. Grâce à un programme que j'ai développé (en Python) pendant ma thèse, j'ai aussi pu étudier l'évolution radiale de la métallicité des galaxies en me basant sur les cubes de donnée MASSIV. Les résultats obtenus concernent la relation masse-métallicité des galaxies à 1<z<2 dans les deux échantillons, ainsi que les gradients radiaux de métallicité dans les galaxies de l'échantillon MASSIV. L'étude de la cinématique des galaxies a parfois été mise à contribution pour expliquer les résultats. Ainsi on a étudié l'évolution et la forme de la relation masse-métallicité. On montre notamment que nos galaxies ont des métallicités faibles, que la forme de la relation n'est pas celle que l'on connaît dans l'univers local, et que les galaxies en interaction dont on détecte le compagnon ont un comportement bien à elles. Concernant les gradients de métallicité, on a pu découvrir une forte portion de gradients positifs ou nuls (un peu plus de la moitié) sur la trentaine de galaxies pour lesquelles nous avons pu le mesurer. Nous avons ensuite appliqué un modèle d'évolution chimique à ces galaxies pour essayer d'estimer des taux d'accrétion.Understanding mass assembly in galaxies along cosmic time is a key issue of galaxy formation and evolution. Today, many projects are intending to find the physical processes at the very origin of galaxy evolution, thanks to integral-field spectroscopy, which allows to get detailed insights into the physical properties of galaxies at different times of the Universe. Thanks to its emission lines, the interstellar medium can be studied quite easily. For now, studies have been able to deduce the kinematics of distant galaxies, et have eventually found large rotating disks already in place at high redshifts (z<3). In the context of the MASSIV project, whose PI is T. Contini, this thesis work is essentially dedicated to the study of the oxygen abundance of 1<z<2 galaxies with the integral-field spectrograph SINFONI at the VLT. The ratio between the nitrogen (NII6584) and hydrogen (Halpha) line has been used to recover the metallicity of the observed gas, thanks to the use of a calibration linking the indicator and the oxygen abundance. After having worked intensively with the data reduction, I was able to recover from the data cubes the metallicity of a first sample of 9 galaxies observed during a pilot run, which aim was to prove the feasibility of the MASSIV project, and of the first sample of the MASSIV project itself. Using a program developed by myself in Python, which works on the data cubes directly, I succeeded in retrieving the radial behavior of metallicity in some MASSIV galaxies. The results we obtained concern mainly the mass-metallicity relation of galaxies at 1<z<2 within both the samples, and the metallicity gradients of the galaxies of the MASSIV sample. From times to times, the study of the kinematics of the galaxies as proven to be a good asset to explain and interpret our results. We have studied the global form and evolution of the mass-metallicity relation. It is shown that our galaxies have low metallicities, that the form of our relation is not the same as in the local universe, and that galaxies for which we have detected an interacting companion have a specific behavior. We have also measured metallicity gradients in 29 galaxies of the MASSIV sample, an important part of which were positive ones (more than the half). We have then tried to apply a chemical evolution model to these galaxies to retrieve an estimation of infall rates of intergalactic metal-poor gas

A chemical survey of exoplanets with ARIEL

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10–100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio

Characterization and modeling of tropospheric propagation at high latitudes for satcom systems

International audienceThe work presented in this paper aims at developing and evaluating the potentialities of a highresolution meteorological model coupled with an electromagnetic module to produce reliable tropospheric attenuation statistics at polar latitudes. To do so, an Atmospheric Numerical Simulator (ANS) based on the high-resolution weather model PWRF-ARW dedicated to polar latitudes is used to generate 3D daily states of the atmosphere in Svalbard (Norway, 80° north latitude) at high spatial (2×2km²) and temporal (5mn) resolutions. Because of considerable computational times, this preliminary work focuses on the simulation of a single day (2017/02/21) during which typical polar precipitations occur. First, the PWRF meteorological outputs relevant for propagation purposes (3D atmospheric datacubes) are compared with reference reanalysis data (Arome-Arctic, CARRA, ERA5) as well as meteorological measurements collected during the THOR7 propagation experiment based on the Svalbard archipelago. Second, an electromagnetic module is used to convert the PWRF meteorological output datacubes into tropospheric attenuation time series simulating the link at Ka band between the THOR7 beacon and the SvalSat teleport. These are compared with the experimental time series collected during the THOR7 propagation experiment. Synthetic attenuation statistics are also produced for that specific day and compared to the experimental statistics derived from the THOR7 propagation experiment. On the 2017/02/21, the results show a good agreement between PWRF outputs and the other meteorological data sources. Additionally, if the synthetic attenuation times series reproduces quite well the experimental time series dynamics, the statistical analysis reveals overestimations that could be explained by either an approximative modeling of the hydrometeors in mixed-phase or wrong predicted hydrometeors contents

Assemblage des galaxies au cours du temps (évolution chimique des galaxies à 1<z<2 avec la spectroscopie 3D)

TOULOUSE3-SCD-Bib. electronique (315559904) / SudocTOULOUSE-Observ. Midi Pyréné (315552299) / SudocSudocFranceF

Characterization and modeling of tropospheric propagation at high latitudes for satcom systems

International audienceThe work presented in this paper aims at developing and evaluating the potentialities of a highresolution meteorological model coupled with an electromagnetic module to produce reliable tropospheric attenuation statistics at polar latitudes. To do so, an Atmospheric Numerical Simulator (ANS) based on the high-resolution weather model PWRF-ARW dedicated to polar latitudes is used to generate 3D daily states of the atmosphere in Svalbard (Norway, 80° north latitude) at high spatial (2×2km²) and temporal (5mn) resolutions. Because of considerable computational times, this preliminary work focuses on the simulation of a single day (2017/02/21) during which typical polar precipitations occur. First, the PWRF meteorological outputs relevant for propagation purposes (3D atmospheric datacubes) are compared with reference reanalysis data (Arome-Arctic, CARRA, ERA5) as well as meteorological measurements collected during the THOR7 propagation experiment based on the Svalbard archipelago. Second, an electromagnetic module is used to convert the PWRF meteorological output datacubes into tropospheric attenuation time series simulating the link at Ka band between the THOR7 beacon and the SvalSat teleport. These are compared with the experimental time series collected during the THOR7 propagation experiment. Synthetic attenuation statistics are also produced for that specific day and compared to the experimental statistics derived from the THOR7 propagation experiment. On the 2017/02/21, the results show a good agreement between PWRF outputs and the other meteorological data sources. Additionally, if the synthetic attenuation times series reproduces quite well the experimental time series dynamics, the statistical analysis reveals overestimations that could be explained by either an approximative modeling of the hydrometeors in mixed-phase or wrong predicted hydrometeors contents

Modélisation du comportement pluriannuel de l'atténuation due à la pluie en bande Ka en Guyane française à l'aide d'un simulateur atmosphérique reposant sur un modèle de prévision météorologique à haute résolution

International audienceCe papier présente l'utilisation d'un simulateur atmosphérique reposant sur un modèle de prévision météorologique à haute résolution pour reproduire des statistiques d'atténuations due à la pluie pluriannuelles en bande Ka en Guyane française. Les résultats obtenus à l'aide de ce modèle sont comparés d'une part aux données expérimentales disponibles dans cette région et d'autre part aux modèles de prévision de l'UIT

Rain Attenuation Estimation with the Numerical Weather Prediction Model WRF: Impact of Rain Drop Size Distribution for a Temperate Climate

International audienceFrequencies at and above K/Ka band are required for the deployment of (very) high throughput satellites. Yet, radio-links at those frequencies are strongly affected by tropospheric constituents, especially rain. The knowledge of the signal attenuation due to rain comes from dedicated propagation experiments with satellite beacons. Numerical Weather Prediction models could act as an alternative source of rain information, but the validation of their performances against beacon data remains incomplete, notably with respect to the local climatology. This work takes a look at the rain attenuation predicted with the Weather Research and Forecasting (WRF) model 4.0.3 initialized with ERA-5 data, tests nine microphysics schemes, either single-or double-moment, and adapts rigorously the electromagnetic model to their assumed rain drop size distributions. Results are compared over three months in Toulouse, in a temperate region, at both 20.2 and 39.4 GHz, and a strategy is outlined to select the best parametrizations from the error metrics

Modélisation du comportement pluriannuel de l'atténuation due à la pluie en bande Ka en Guyane française à l'aide d'un simulateur atmosphérique reposant sur un modèle de prévision météorologique à haute résolution

International audienceCe papier présente l'utilisation d'un simulateur atmosphérique reposant sur un modèle de prévision météorologique à haute résolution pour reproduire des statistiques d'atténuations due à la pluie pluriannuelles en bande Ka en Guyane française. Les résultats obtenus à l'aide de ce modèle sont comparés d'une part aux données expérimentales disponibles dans cette région et d'autre part aux modèles de prévision de l'UIT

FREQUENCY SCALING OF RAIN ATTENUATION FOR VERY HIGH THROUGHPUT SATELLITE SYSTEMS

International audienceIn this paper, we present a methodology to compare frequency scaling techniques of rain attenuation. This methodology consists in obtaining rain attenuation from beacon measurements, selecting a subset of events, and applying metrics on the obtained time series. Are also discussed methodologies to separate the contributions of clouds and rain to attenuation, as well as a method to identify events affected by noise. The relevance of the approaches is evaluated on a database of satellite beacon attenuation: Italsat beacon measurements from Spino d'Adda (7 years)