I. Vauglin

Extragalactic database - VII. Reduction of astrophysical parameters

The Lyon-Meudon Extragalactic database (LEDA) gives a free access to the main astrophysical parameters for more than 100 000 galaxies. The most common names are compiled allowing users to recover quickly any galaxy. All these measured astrophysical parameters are first reduced to a common system according to well defined reduction formulae leading to mean homogeneized parameters. Further, these parameters are also transformed into corrected parameters from widely accepted models. For instance, raw 21-cm line widths are transformed into mean standard widths after correction for instrumental effect and then into maximum velocity rotation properly corrected for inclination and non-circular velocity. This paper presents the reduction formulae for each parameter: coordinates, morphological type and luminosity class, diameter and axis ratio, apparent magnitude (UBV , IR, HI) and colors, maximum velocity rotation and central velocity dispersion, radial velocity, mean surface brightness, distance modulus and absolute magnitude, and group membership. For each of these parameters intermediate quantities are given: galactic extinction, inclination, K-correction etc.. All these parameters are available from direct connexion to LEDA and distributed on a standard CD-ROM (PGC-ROM 1996) by the Observatoire de Lyon via the CNRS.

DENIS: A DEEP NEAR-INFRARED SURVEY OF THE SOUTHERN SKY

The DENIS project is the first attempt to carry out a complete digitized survey of the southern sky in the range 1–2.5µm. The main objectives of the programme and the main specifications of the camera and of the data processing stream are briefly outlined

First DENIS I-band extragalactic catalog

This paper presents the rst I-band photomet- ric catalog of the brightest galaxies extracted from the Deep Near Infrared Survey of the Southern Sky (DENIS) An automatic galaxy recognition program has been de- veloped to build this provisional catalog. The method is based on a discriminating analysis. The most discrimi- nant parameter to separate galaxies from stars is proved to be the peak intensity of an object divided by its ar- ray. Its eciency is better than 99%. The nominal ac- curacy for galaxy coordinates calculated with the Guide Star Catalog is about 6 arcsec. The cross-identication with galaxies available in the Lyon-Meudon Extragalactic DAtabase (LEDA) allows a calibraton of the I-band pho- tometry with the sample of Mathewson et Al. Thus, the catalog contains total I-band magnitude, isophotal di- ameter, axis ratio, position angle and a rough estimate of the morphological type code for 20260 galaxies. The internal completeness of this catalog reaches magnitude Ilim =1 4 :5, with a photometric accuracy of 0:18 m. 25% of the Southern sky has been processed in this study. This quick look analysis allows us to start a radio and spectrographic follow-up long before the end of the survey.

Serendipitous detection of galaxies behind the Milky Way from the DENIS survey

A search has been undertaken at Lyon Observatory to identify, by eye, galaxy candidates at galactic latitudes lower than15 degrees on the DENIS J and K-band images. This paper presents a list of 2028 objects that were serendipitously detected throughout the DENIS survey. Cross-identication with galaxy entries in the LEDA Database has been performed. Comparison with the second release of the 2MASS survey led to a satisfactory agreement of J band magnitudes (std. dev. = 0.3 mag). The distribution of galaxy candidates along the Galactic Plane shows a concentration near the galactic longitude l = 305 deg. As a by product of this inspection of J and K images some interesting galactic objects were found (star clusters and nebulae).

LEDA: The Lyon-Meudon Extragalactic Database

In 1981 our scientific team was involved in the management of large amount of HI-data. The goal, at this time, was only our own scientific research. In a collaboration with G. and A. de Vaucouleurs we started to add optical information to our first HI-catalog. It was our first contact with the difficult problem of cross-identifying two catalogs and merging them. To face this problem, one of us (GP) decided to rationalize the management by creating a database. It was created in 1983 at Lyon Observatory. LEDA is thus the oldest Extragalactic Database. Since this time, the database has been continuously updated and improved.

A European vision for a "Polar Large Telescope'' project

The Polar Large Telescope (PLT) project is primarily aimed at undertaking large, wide band synoptic astronomical surveys in the infrared in order to provide critical data to the forthcoming generation of observational facilities such as ALMA, JWST, LSST and the E-ELT, and to complement the observations obtained with them. Sensitive thermal IR surveys beyond 2.3 μm cannot be carried out from any existing ground based observatory and the Antarctic Plateau is the only place on the ground where it can be envisaged, thanks to its unique atmospheric and environmental properties, such as the turbulence profile (image quality), the low opacity and the reduced thermal background emission of the sky. These unique conditions enable high angular resolution wide field surveys in the near thermal infrared (2.3-5 μm). This spectral range is particularly well suited to tackling key astrophysical questions such as: i) investigating the nature of the distant universe, the first generation of stars and the latest stages of stellar evolution, ii) understanding transient phenomena such as gamma ray-bursts and Type Ia supernovae, iii) increasing our knowledge of extra-solar planets. Further instruments may broaden the expected science outcomes of such a 2-4 m class telescope especially for the characterization of galaxies at very large distance to provide new clues in the mysteries of dark matter and energy. Efforts will be made to merge this project with other comparable projects within an international consortium.