Extragalactic database. VII Reduction of astrophysical parameters

TL;DR

This paper details the methods used to homogenize and correct astrophysical parameters for over 100,000 galaxies in the LEDA database, facilitating consistent and comparable galaxy data analysis.

Contribution

It introduces standardized reduction formulae for various galaxy parameters, enabling uniform data correction and transformation in the LEDA extragalactic database.

Findings

Parameters are homogenized using well-defined reduction formulae.

Corrected parameters account for instrumental and physical effects.

Data is accessible via direct connection and on CD-ROM.

Abstract

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 (telnet lmc.univ-lyon1.fr, login: leda, no passwd OR http://www-obs.univ-lyon1.fr/leda ) and distributed on a standard CD-ROM (PGC-ROM 1996) by the Observatoire de Lyon via the CNRS (mail to petit@obs.univ-lyon1.fr).