Déconvolution de données hyper-spectrales en astronomie

National audienceCe papier présente une méthode de déconvolution de données hyper-spectrales prenant en compte les correlations spatiales et spectrales de la scène observée. Pour cela nous introduisons une régularization séparable appliquée à l'objet renormalisé pour tenir compte de la dynamique des objets observé. Il ne reste ainsi que deux hyper-paramètres qui restent à près constant d'une observation à l'autre. Cette méthode a été appliquée avec succès tant à des données simulées qu'à des données réelles provenant du spectrographe SNIFS de la Nearby SuperNova factory

4D deconvolution and demixing for supernova follow-up

4 pagesInternational audienceWe present an inverse problem approach to jointly solve a problem of deconvolution and demixing of sources from 4D (x, y, λ, t) astronomical data obtained by observing a super- nova and its host galaxy at different epochs. In order to obtain supernova spectra of high photometric quality, we take special care of avoiding demixing biases and deconvolution artifacts caused by the very limited size of the field of view. We assert the performances of our method on realistic simulated data

Restoration of hyperspectral astronomical data from Integral field spectrograph

International audienceIn this paper we present a method for hyper-spectral image restoration for integral field spectrographs (IFS) data. It takes advantage of all the spectral and spatial correlations in the observed scene to enhance the spatial resolution. We illustrate this method with simulations coming from the Multi Unit Spectroscopic Explorer (MUSE) instrument. It shows the clear increase of the spatial resolution provided by our method as well as its denoising capability

Heterogeneous Multidimensional Data Deblurring

International audienceWe present a new scheme for deconvolution of heterogeneous multidimensional data (\eg spatio-temporal or spatio-spectral). It is derived, in a very general way, following an inverse problem approach. This method exploits the continuity of both object and PSF along the different dimensions to elaborate separable constraints. This improves the effectiveness and the robustness of the deconvolution technique. We demonstrate these improvements by processing real X-ray video sequences $(x,y,t)$ and astronomical multi-spectral images $(x,y,\lambda)$

Measurement of telescope transmission using a Collimated Beam Projector

With the increasingly large number of type Ia supernova being detected by current-generation survey telescopes, and even more expected with the upcoming Rubin Observatory Legacy Survey of Space and Time, the precision of cosmological measurements will become limited by systematic uncertainties in flux calibration rather than statistical noise. One major source of systematic error in determining SNe Ia color evolution (needed for distance estimation) is uncertainty in telescope transmission, both within and between surveys. We introduce here the Collimated Beam Projector (CBP), which is meant to measure a telescope transmission with collimated light. The collimated beam more closely mimics a stellar wavefront as compared to flat-field based instruments, allowing for more precise handling of systematic errors such as those from ghosting and filter angle-of-incidence dependence. As a proof of concept, we present CBP measurements of the StarDICE prototype telescope, achieving a standard (1 sigma) uncertainty of 3 % on average over the full wavelength range measured with a single beam illumination

Slitless spectrophotometry with forward modelling: principles and application to atmospheric transmission measurement

In the next decade, many optical surveys will aim to tackle the question of dark energy nature, measuring its equation of state parameter at the permil level. This requires trusting the photometric calibration of the survey with a precision never reached so far, controlling many sources of systematic uncertainties. The measurement of the on-site atmospheric transmission for each exposure, or on average for each season or for the full survey, can help reach the permil precision for magnitudes. This work aims at proving the ability to use slitless spectroscopy for standard star spectrophotometry and its use to monitor on-site atmospheric transmission as needed, for example, by the Vera C. Rubin Observatory Legacy Survey of Space and Time supernova cosmology program. We fully deal with the case of a disperser in the filter wheel, which is the configuration chosen in the Rubin Auxiliary Telescope. The theoretical basis of slitless spectrophotometry is at the heart of our forward model approach to extract spectroscopic information from slitless data. We developed a publicly available software called Spectractor (https://github.com/LSSTDESC/Spectractor) that implements each ingredient of the model and finally performs a fit of a spectrogram model directly on image data to get the spectrum. We show on simulations that our model allows us to understand the structure of spectrophotometric exposures. We also demonstrate its use on real data, solving specific issues and illustrating how our procedure allows the improvement of the model describing the data. Finally, we discuss how this approach can be used to directly extract atmospheric transmission parameters from data and thus provide the base for on-site atmosphere monitoring. We show the efficiency of the procedure on simulations and test it on the limited data set available.Comment: 30 pages, 36 figures, submitted to Astronomy and Astrophysic

Deconvolution of (x ,y, wavelength) images

International audienceCurrently, image deconvolution receives increasing attention from the academic world. However, few works have been done in deconvolution of data with heterogeneous dimensions, for example (x, y, depth, wavelength, time...). Following an inverse problem approach, we propose to use physical correlations in the wavelengths and time axes to constraint deconvolution problem. It leads to a faster and a better reconstruction than successive images deconvolution. Moreover, in some cases, it leads to a very effective blind deconvolution scheme(deconvolution of observation blurred by an unknown process). We present deconvolution of (x,y,wavelength) data cubes from the SuperNova factory. (The SuperNova factory is a survey using an integral field spectrograph to observe spectro-photometrically Type Ia supernovae (SNeIa) in the redshift range 0.0

Partage et libération de composés d'arôme dans des matrices laitières émultionnées et gélifiées modèles de yaourts brassés

Pour dégager étapes de formulation et facteurs de composition: teneur et nature de la matière grasse, et de structure modifiant la disponibilité de l'arôme dans les yaourts brassés, des matrices laitières modèles: émulsion, et gels brassés, ont été élaborées et leurs propriétés mécaniques et leur structure, incluant la composition protéique des interfaces ont été caractérisées. L'étude du partage et de la libération des composés d'arôme a permis de montrer que la rétention des composés d'arôme hydrophobes augmente avec la teneur en matière grasse liquide. Leur vitesse de libération est liée à la teneur en matière grasse liquide dans le cas des émulsions et au seuil d'écoulement dans le cas des gels. Au delà de 30g.kg-1 de lipides, seule la fraction de matière grasse liquide doit être intégrée aux modèles de prédiction du partage. Pour les faibles teneurs en matière grasse, composition et structure de la phase continue doivent être prises en compte pour prédire partage et libération.This work aimed to sort the keys factors that modified the behavior of aroma compounds in models of stirred yogurts. Complex matrices were designed by varying the amount and the nature of emulsified fat as well as the organization of the continuous phase (emulsions vs stirred gels). Mechanical properties, structure of matrices and protein load and composition at the interface were characterized. Retention of hydrophobic aroma compounds was mainly related to the amount of liquid fat and to a lesser extent to the organization of the continuous phase. The release rate was related to the amount of liquid fat in emulsions and to the yield stress in stirred gels. Above 30 g.kg-1 of liquid fat, partition coefficients over emulsions and stirred gels can be predicted from behavior over liquid fat and water only. Below this value, composition and organization of the continuous phase must be taken into account.NANTES-BU Sciences (441092104) / SudocSudocFranceF

Radiation transfer and type a [ia] supernovae spectra analysis in the context of supernovae factory

Dans cette thèse, effectuée en cotutelle avec l'Université d'Oklahoma City, nous avons étudié le transfert radiatif dans les enveloppes en expansion rapide des supernovae de type Ia (SNeIa) dans le cadre de la collaboration SupernovaeFactory. Ces étoiles qui explosent avec une luminositée comparable à celle d'une galaxie sont utilisées comme chandelles standard permettant d'étudier le comportement à grande échelle de l'univers. Nous avons utilisé le code de transfert radiatif PHOENIX développé par P.Hauschildt, F.Allard et E.Baron, pour simuler des spectres de SNeIa à différentes dates et luminosités afin d'étudier le processus de formation spectrale. Nous avons parallèlement élaboré un module de grille adaptative qui augmente sa robustesse de convergence. Nous avons montré que la formation des spectres de SNeIa n'était pas aussi localisée que dans le modèle photospherique standard mais qu'elle mettait en relation des régions allant de 5000 km/s à 20000 km/s pour des époques proches du maximum de luminosité. Nous avons de plus développé des indicateurs spectraux permettant de mesurer la luminosité des SNeIa avec une précision égale à celle des méthodes basées sur l'analyse des courbes de lumière. Il devient ainsi possible de contraindre de façon indépendante l'évolution des SNeIa avec le redshift, ce qui place ce travail à l'interface entre l'étude des supernovae en tant qu'objets stellaires et leur utilisation en cosmologieLYON1-BU.Sciences (692662101) / SudocSTRASBOURG-Bib.Central Recherche (674822133) / SudocSudocFranceF

Temperature effect on solubility of aroma compounds in various aqueous solutions

International audienceSolubility of nine aroma compounds (methyl ketones, ethyl esters, aldehyde and alcohol) in various aqueous solutions was measured by the mutual solubility method from -10 to +10degreesC. Influence of both, the nature (carbohydrates and polyols) and the substrate concentration (from 0 to 57.5g/100g) on aroma solubility in aqueous solutions was studied. Aroma solubility in water decreased when aroma hydrophobicity increased. Aroma solubility in various aqueous solutions decreased when substrate concentration increased; their solubility was higher in polyols solutions than in polysaccharides ones. Temperature effect on aroma solubility showed a noncontinuous evolution for solutions without ice: from +25 to +4degreesC, solubility decreased, then from +4 to -5degreesC, solubility increased. Finally, from -5 to -10degreesC solubility decreased once again. The same behavior was observed for all studied media. Comparison with other characteristics (such as density and water structure) of the aqueous solutions was done in order to better understand this temperature effect on aroma solubility