3 Description of the catalogue

  The catalogue consists of four separate files:

1.

Compiled and aperture corrected measurements of Mg₂ indices (Table 1);

2.

Observational parameters of each dataset (Table 2, available both in the text and in the electronic form at CDS);

3.

Bibliography (Table 3);

4.

Standard mean values of Mg₂ indices (Table 4).

3.1 The list of raw/compiled measurements of Mg₂ indices

The list contains the "raw" Mg₂-index in magnitudes, as given in the original publications. Observational setup and corrections possibly applied by the authors are described in the parameters file.

Each object is indexed by its normalized identifier. The galaxy identifiers follow the rule already used in Prugniel & Simien (1996 - hereafter PS96) and in Prugniel et al. (1998). Whenever it was possible, the identifier was chosen along the hierarhy NGC/IC, UGC/ESO, PGC. The original author's identifier is adopted when the cross-identification through NED or LEDA failed.

Beside the raw measurements we provide the aperture corrected and zero-pointed data (see Sect. 2).

Each measurement refers to a dataset which is expanded into its bibliographic reference in the bibliographic file and whose parameters are listed in the parameters file.

A flag on each Mg₂ index measurement is provided which describes its status (regular, discrepant, preliminary or republished, or a compilation value).

Only regular measurements are used to compute the mean standard values. Thus, the data from the $7\ Samurai$ have been used as different datasets as published by Davies et al.(1987).

3.2 The list of the observational parameters

The description of each dataset is organised in a way which allow to make the corrections needed to bring given measurement in homogeneous system of values. These parameters describe the size of the slit, or the physical size of the aperture. The dataset's mean zero-point corrections determined by us as well as the corresponding re-scaled internal errors of the datasets are provided.

3.3 The list of the bibliography

The dataset acronyms are linked to the CDS/ADS BIBCODE (http://simbad.u-strasbg.fr/biblio/biblio.html) and to the full text of the reference.

3.4 The list of adopted Mg₂ values

For 1060 galaxies an 37 globular clusters we list in this file the mean value of the Mg₂ accompanied with the corrected flow-smoothed velocity we used for computing the aperture correction, and with a flag specifying if the value is given or not in the homogeneous system. The globular clusters do not belong to the homogeneous system. The definition of our standard homogeneous system is discussed in Sect. 2 above. This list is sorted by increasing of R.A.