Astron. Astrophys. 330, 819-822 (1998)

2. Observations and data analysis

Spectroscopic observations were made at the 3.5m telescope on Calar Alto using the Boller&Chivens TWIN spectrograph. The spectra cover the wavelength range Å and have an instrumental resolution of . The exposure time was 1 h. The CCD images were reduced in the usual way and the spectra were extracted and integrated with an algorithm introduced by Horne (1986). Absorption line indices of H , Mg₂, Mg , Fe 5 ( Å) and Fe 6 ( Å) were measured in the one-dimensional spectra following Faber et al. (1985). They were corrected for velocity dispersion broadening and normalized to the Lick system by means of observed reference stars. Velocity dispersions were derived using the FCQ-method by Bender (1990). Details of the observational set-up, the reduction procedure and the derivation of the data can be found in Ziegler & Bender (1997).

To get an estimate of the apparent size, surface brightness and total brightness, the Leo galaxies were imaged with a CCD camera at the 80 cm telescope of the Wendelstein Observatory. A filter corresponding to the Cousins R band was used. A calibration accurate to about 0.1 mag was achieved by the observation of the standard star cluster NGC 4147 (Christian et al., 1985), which is located in the vicinity of the Leo group. The effective radius (), effective surface brightness at (SB_e) and total apparent magnitude () were derived with the isophote fitting technique introduced by Bender & Möllenhoff (1987) and using an growth curve.

© European Southern Observatory (ESO) 1998

Online publication: January 27, 1998
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