6 research outputs found
FALCON: a concept to extend adaptive optics corrections to cosmological fields
FALCON is an original concept for a next generation spectrograph at ESO VLT
or at future ELTs. It is a spectrograph including multiple small integral field
units (IFUs) which can be deployed within a large field of view such as that of
VLT/GIRAFFE. In FALCON, each IFU features an adaptive optics correction using
off-axis natural reference stars in order to combine, in the 0.8-1.8 \mu m
wavelength range, spatial and spectral resolutions (0.1-0.15 arcsec and
R=10000+/-5000). These conditions are ideally suited for distant galaxy
studies, which should be done within fields of view larger than the galaxy
clustering scales (4-9 Mpc), i.e. foV > 100 arcmin2. Instead of compensating
the whole field, the adaptive correction will be performed locally on each IFU.
This implies to use small miniaturized devices both for adaptive optics
correction and wavefront sensing. Applications to high latitude fields imply to
use atmospheric tomography because the stars required for wavefront sensing
will be in most of the cases far outside the isoplanatic patch.Comment: To appear in the Backaskog "Second Workshop on ELT" SPIE proceeding
Functional Interactions between the erupted/tsg101 Growth Suppressor Gene and the DaPKC and rbf1 Genes in Drosophila Imaginal Disc Tumors
BACKGROUND: The Drosophila gene erupted (ept) encodes the fly homolog of human Tumor Susceptibility Gene-101 (TSG101), which functions as part of the conserved ESCRT-1 complex to facilitate the movement of cargoes through the endolysosomal pathway. Loss of ept or other genes that encode components of the endocytic machinery (e.g. synatxin7/avalanche, rab5, and vps25) produces disorganized overgrowth of imaginal disc tissue. Excess cell division is postulated to be a primary cause of these 'neoplastic' phenotypes, but the autonomous effect of these mutations on cell cycle control has not been examined. PRINCIPAL FINDINGS: Here we show that disc cells lacking ept function display an altered cell cycle profile indicative of deregulated progression through the G1-to-S phase transition and express reduced levels of the tumor suppressor ortholog and G1/S inhibitor Rbf1. Genetic reductions of the Drosophila aPKC kinase (DaPKC), which has been shown to promote tumor growth in other fly tumor models, prevent both the ept neoplastic phenotype and the reduction in Rbf1 levels that otherwise occurs in clones of ept mutant cells; this effect is coincident with changes in localization of Notch and Crumbs, two proteins whose sorting is altered in ept mutant cells. The effect on Rbf1 can also be blocked by removal of the gamma-secretase component presenilin, suggesting that cleavage of a gamma-secretase target influences Rbf1 levels in ept mutant cells. Expression of exogenous rbf1 completely ablates ept mutant eye tissues but only mildly affects the development of discs composed of cells with wild type ept. CONCLUSIONS: Together, these data show that loss of ept alters nuclear cell cycle control in developing imaginal discs and identify the DaPKC, presenilin, and rbf1 genes as modifiers of molecular and cellular phenotypes that result from loss of ept
Apport de la haute resolution angulaire sur l'etude des galaxies lointaines : imagerie, optique adaptative et spectroscopie 3D
The PhD work presented here is related to the study of distant galaxies, whose studies are required to understand the mecanisms responsibles of galaxy formation. The Hubble Space Telescope has allowed to provide high-resolution images of distant galaxies, thus giving first clues about their morphology. In addition, the 8-10 meters telescopes like the european Very Large Telescope (VLT) located at the ground have given spectroscopic informations about these objects. The combination of all these data shows that there was a burst of star formation in the universe some 8-10 billions years ago, which has since declined. The first part of this thesis deals with morphological studies of distant galaxies from Hubble Space Telescope images. Two galaxy's populations were analysed : luminous compact galaxies (LCG) and luminous infrared galaxies (LIRG), which are both responsible of the star formation decline shown before. Those studies have allowed to build a sequence who could give a scenario of the formation of some galaxies in today's universe. Additional studies have also shown the requirement of a high spectral resolution to compute precise star formation rates in distant galaxies. The second part of this thesis is related to the study of FALCON, a project of new generation spectrograph for the VLT, who will provide high angular and spectral resolution. FALCON's goal is to get the dynamical information of distant galaxies with a spatial resolution of 0.25 arcsec with a sufficient signal-to-noise ratio. This requires to use Adaptive Optics to compensate in real-time for image degradation due to atmospheric turbulence. In order to not suffer from anisoplanatism, FALCON will use atmospheric tomography. This consists in combining measurements from off-axis wavefront-sensors around the galaxy to correct its wavefront by using a deformable mirror, so that its dynamic can be measured. The adaptive optics system has first been studied theoritically. Then the development of a simulation tool has allowed to compute some first performances of such a system on the sky.Cette thèse se place dans le contexte de l'étude des galaxies lointaines, études nécessaires à la compréhension des mécanismes de formation des galaxies. La mise en service du télescope spatial Hubble a permis d'obtenir des images à haute résolution spatiale de ces galaxies, donnant ainsi des premiers indices sur leur morphologie. En complément, l'installation de télescopes au sol de la classe des 8-10 mètres tels que le Very Large Telescope (VLT) européen a permis d'effectuer la spectroscopie de ces objets. Toutes ces données montrent que l'univers a connu un pic de formation stellaire il y a environ 8-10 milliards d'années, formation qui a chuté depuis. La première partie de ce manuscrit est consacrée à l'étude de la morphologie des galaxies lointaines, à l'aide d'images obtenues avec le télescope spatial Hubble. Le travail présenté porte en particulier sur deux populations de galaxies responsables du déclin de la formation stellaire évoqué plus haut : les galaxies compactes lumineuses (LCG) et les galaxies lumineuses dans l'infrarouge (LIRG). Ces études ont notamment permis d'établir une séquence pouvant servir de base à un scénario de formation d'une partie des galaxies de l'univers local. Des études complémentaires ont aussi montré le besoin d'une haute résolution spectrale pour déterminer avec précision le taux de formation stellaire des galaxies lointaines. La deuxième partie est consacrée à l'étude de FALCON, un projet de spectrographe de nouvelle génération pour le VLT alliant haute résolution spatiale et spectrale. L'objectif de FALCON est de fournir l'information dynamique sur les galaxies lointaines avec une résolution spatiale de 0.25 arcsec et un rapport signal-sur-bruit suffisant. Ceci nécessite d'utiliser l'Optique Adaptative pour compenser en temps-réel la dégradation des images due à la turbulence. Afin de s'affranchir de l'anisoplanétisme propre à cette technique, FALCON utilisera des techniques de tomographie consistant à corriger le front d'onde issu de la galaxie dont on souhaite déterminer la dynamique en combinant les mesures de front d'onde sur des étoiles hors-axe qui l'entourent. Le système d'Optique Adaptative a d'abord été intensivement étudié de manière théorique. Puis le développement d'un code de simulation numérique a alors permis d'établir des premières performances d'un tel système sur le ciel
Analyse de la mise en place du système foliaire et des organes reproducteurs du maïs en fonction de la contrainte hydrique
National audienc
A multi-object multi-field spectrometer and imager for a European ELT
One of the highlights of the European ELT Science Case book is the study of
resolved stellar populations, potentially out to the Virgo Cluster of galaxies.
A European ELT would enable such studies in a wide range of unexplored distant
environments, in terms of both galaxy morphology and metallicity. As part of a
small study, a revised science case has been used to shape the conceptual
design of a multi-object, multi-field spectrometer and imager (MOMSI). Here we
present an overview of some key science drivers, and how to achieve these with
elements such as multiplex, AO-correction, pick-off technology and spectral
resolution.Comment: 9 pages, 8 figures, to be published in Proc. SPIE 6269, Ground-based
& Airborne Instrumentation for Astronom