The EFIGI catalogue of 4458 nearby galaxies with detailed morphology

Accepted for publication in Astronomy and Astrophysics, 27 pages, 7 tables, 32 colour figures. Data available at http://www.efigi.orgInternational audienceNow that large databases of resolved galaxy images are provided by modern imaging surveys, advanced morphological studies can be envisioned, urging for well defined calibration samples. We present the EFIGI catalogue, a multiwavelength database specifically designed for a dense sampling of all Hubble types. The catalogue merges data from standard surveys and catalogues (Principal Galaxy Catalogue, Sloan Digital Sky Survey, Value-Added Galaxy Catalogue, HyperLeda, and the NASA Extragalactic Database) and provides detailed morphological information. Imaging data are obtained from the SDSS DR4 in the u, g, r, i, and z bands for a sample of 4458 PGC galaxies, whereas photometric and spectroscopic data are obtained from the SDSS DR5 catalogue. Point-Spread Function models are derived in all five bands. Composite colour images of all objects are visually examined by a group of astronomers, and galaxies are staged along the Hubble sequence and classified according to 16 morphological attributes describing their structure, texture, as well as environment and appearance on a five-level scale. The EFIGI Hubble sequence shows remarkable agreement with the RC3 Revised Hubble Sequence. The main characteristics and reliability of the catalogue are examined, including photometric completeness, type mix, systematic trends and correlations. The final EFIGI database is a large sub-sample of the local Universe, with a dense sampling of Sd, Sdm, Sm and Im types compared to magnitude-limited catalogues. We estimate the photometric catalogue to be more than ~ 80% complete for galaxies with 10 < g < 14. More than 99.5% of EFIGI galaxies have a known redshift in the HyperLeda and NED databases

The polarized dust shell around alpha Orionis. II The silicon fractional condensation, mass-loss rate and grain radius

International audienc

The polarized dust shell around alpha Orionis. II The silicon fractional condensation, mass-loss rate and grain radius

International audienc

Widening the application of AATSR SST data to operational tasks through the Medspiration Service

For over a decade the ATSR series of sensors produced high quality SST data products, but the narrow swath did not encourage their use for operational tasks. This changed in 2005 when the European Space Agency's Medspiration Service introduced AATSR data in the GHRSST L2P format. This paper describes the opportunities provided by the Medspiration system for facilitating the complementary use of SST products from AATSR and from other satellite sensors. It explains how, following the implementation by Medspiration of GHRSST procedures, data products and tools, AATSR data are now being used around the world to complement the use of other sources of SST and to facilitate bias adjustments between them. Despite the limited daily coverage of AATSR its broadly reliable accuracy and stability seem to be beneficial to SST analyses that merge all available observations. The new analyses are already contributing to improved ocean and weather forecasting. This represents an unforeseen but significant role for the ATSR series, through which it continues to make an important contribution to the operational uses of SST

Spectroscopic confirmation of redshifts predicted by gravitational lensing

We present deep spectroscopic measurements of 18 distant field galaxies identified as gravitationally-lensed arcs in a Hubble Space Telescope image of the cluster Abell 2218. Redshifts of these objects were predicted by Kneib et al. (1996) using a lensing analysis constrained by the properties of two bright arcs of known redshift and other multiply-imaged sources. The new spectroscopic identifications were obtained using long exposures with the LDSS-2 spectrograph on the William Herschel Telescope and demonstrate the capability of that instrument to new limits, $R\simeq$24; the lensing magnification implies true source magnitudes as faint as $R\simeq$25. Statistically, our measured redshifts are in excellent agreement with those predicted from Kneib et al.'s lensing analysis which gives considerable support to the redshift distribution derived by the lensing inversion method for the more numerous and fainter arclets extending to $R\simeq 25.5$. We explore the remaining uncertainties arising from both the mass distribution in the central regions of Abell 2218 and the inversion method itself, and conclude that the mean redshift of the faint field population at $R\simeq$25.5 ($B\sim 26$-27) is low, $$=0.8-1. We discuss this result in the context of redshift distributions estimated from multi-colour photometry. Although such comparisons are not straightforward, we suggest that photometric techniques may achieve a reasonable level of agreement particularly when they include near-infrared photometry with discriminatory capabilities in the $1<z<$2 range.Comment: 20 pages, LaTeX, 18 figures. Submitted to MNRAS. Figures 1,8,9,10 & 11 and whole paper available at ftp://ftp.ast.cam.ac.uk/pub/tebbels/a2218inv

COLNACOQ. Composés lipophiles naturels dans l’environnement des coquillages. Rapport final

Cette étude s’est inscrite dans un contexte d’évaluation de la salubrité des mollusques bivalves destinés à la consommation humaine. Ces organismes peuvent en effet accumuler des toxines, en particulier de microalgues, en concentrations importantes, pouvant induire des intoxications chez les personnes les consommant. Afin d’assurer la protection des consommateurs, les toxines réglementées sont recherchées dans les coquillages par techniques physico-chimiques. En parallèle, les toxines émergentes, potentiellement produites par d’autres organismes que les micro-algues telles que les micromycètes, peuvent être detectées par l’utilisation du test de toxicité aigüe sur souris. Cependant, ce bio-essai présente de très nombreux inconvénients, notamment éthiques et méthodologiques. C’est pourquoi une suite de bio-essais miniaturisés a été développée en utilisant trois types de tests : cytotoxicité sur cellules KB, la toxicité aguë sur larves de diptères, et activités antibactériennes sur bactéries marines. Ces tests ont dans un premier temps été adaptés à des protocoles de routine, puis leur périmètre de détection a été évalué à différents niveaux de complexité de la matrice : toxine lipophile pure connue ou émergente, extrait brut de micro-algue ou de micromycète producteur de toxine, et matrices de bivalves dopées par des toxines. Les trois tests se sont révélés être complémentaires dans leurs champs de détection, et une démarche pour leur mise en place a pu été proposée. Une douzaine de souches de microalgues et 24 souches de micromycètes ont été cultivées et testées avec la suite de bio-essais. Pour certaines souches de micro-algues et de micromycètes de nouveaux composés ont pu être mis en évidence. En s’appuyant sur des techniques de spectrométrie de masse haute résolution, des exercices de déréplication ont été entrepris pour deux organismes en particulier : le dinoflagellé Vulcanodinium rugosum et le micromycète Beauveria brongniartii. La procédure développée a été validée pour la matrice coquillage et pourra de ce fait être utilisé dans le cadre de recherche de composés toxiques dans cette matrice, notamment dans les dispositifs nationaux de vigilance alimentaire