  This is the first paper of a series focused on investigating the star
formation and evolutionary history of the two early-type galaxies NGC 1407 and
NGC 1400. They are the two brightest galaxies of the NGC 1407 (or Eridanus-A)
group, one of the 60 groups studied as part of the Group Evolution
Multi-wavelength Study (GEMS). Here we present new high signal-to-noise
long-slit spectroscopic data obtained at the ESO 3.6m telescope and
high-resolution multi-band imaging data from the HST/ACS and wide-field imaging
from Subaru Suprime-Cam. We spatially resolved integrated spectra out to 0.6
(NGC 1407) and 1.3 (NGC 1400) effective radii. The radial profiles of the
kinematic parameters v(rot), sigma, h3 and h4 are measured. The surface
brightness profiles are fitted to different galaxy light models and the colour
distributions analysed. The multi-band images are modelled to derive isophotal
shape parameters and residual galaxy images. The parameters from the surface
brightness profile fitting are used to estimate the mass of the possible
central supermassive black hole in NGC 1407. The galaxies are found to be
rotationally supported and to have a flat core in the surface brightness
profiles. Elliptical isophotes are observed at all radii and no fine structures
are detected in the residual galaxy images. From our results we can also
discard a possible interaction between NGC 1400, NGC 1407 and the group
intergalactic medium. We estimate a mass of 1.03x10^9 M(sun) for the
supermassive black hole in NGC 1407 galaxy.
