Line-strength indices and velocity dispersions for 148 early-type galaxies in different environments^*

¹ Instituto Astronômico e Geofísico, Universidade de São Paulo, Avenida Miguel Stéfano 4200, 04301-904 São Paulo, SP, Brazil
² Universitäts-Sternwarte München, Scheinerstr. 1, 81679 München, Germany

Corresponding author: D. Thomas, dthomas@mpe.mpg.de

Received: 30 July 2001
Accepted: 26 August 2002

Abstract

We have derived high quality line-strength indices and velocity dispersions for a sample of 148 early-type galaxies in different environments. The wavelength region covered by the observations ( to 6600 Å) includes the Lick/IDS indices H, Mg₁, Mg₂, Mgb, Fe5015, Fe5270, Fe5335, Fe5406, Fe5709, Fe5782, NaD, TiO₁ and TiO₂. The data are intended to address possible differences of the stellar populations of early-type galaxies in low- and high-density environments. This paper describes the sample properties, explains the data reduction and presents the complete list of all the measurements. Most galaxies of the sample (85%) had no previous measurements of any Lick/IDS indices and for 30% of the galaxies we present first-time determinations of their velocity dispersions. Special care is taken to identify galaxies with emission lines. We found that 62 per cent of the galaxies in the sample have emission lines, as measured by the equivalent width of the [OIII] 5007Å line, EW[OIII] > 0.3 Å.