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

Algorithme de calcul de l'arbre des composantes avec applications à la reconnaissance des formes en imagerie satellitaire

Cet article présente un nouvel algorithme de calcul de l'arbre des composantes d'une image. Vis-à-vis de l'état de l'art, cet algorithme ne fait pas un usage excessif de la mémoire et travaille efficacement sur les images dont les valeurs ont une forte quantification et sur les images à valeurs à virgule flottante. Nous décrivons également une application de cet algorithme à l'identification d'objets pertinents dans des images d'astronomie

Probeless and Realistic Mixed Reality Application in Presence of Dynamic Light Sources

International audienceIn this work, we consider the challenge of achieving a coherent blending between real and virtual worlds in the context of a Mixed Reality (MR) scenario. Specifically, we have designed and implemented an interactive demonstrator that shows a realistic MR application without using any light probe. The proposed system takes as input the RGB stream of the real scene, and uses these data to recover both the position and intensity of light sources. The lighting can be static and/or dynamic and the geometry of the scene can be partially altered. Our system is robust in presence of specular effects and handles both uniform and/or textured surfaces