Low X-Ray Luminosity Galaxy Clusters: Main goals, sample selection,
  photometric and spectroscopic observations
  We present the study of nineteen low X-ray luminosity galaxy clusters (L$_X
\sim$ 0.5--45 $\times$ $10^{43}$ erg s$^{-1}$), selected from the ROSAT
Position Sensitive Proportional Counters (PSPC) Pointed Observations (Vikhlinin
et al. 1998) and the revised version of Mullis et al. (2003) in the redshift
range of 0.16 to 0.7. This is the introductory paper of a series presenting the
sample selection, photometric and spectroscopic observations and data
reduction. Photometric data in different passbands were taken for eight galaxy
clusters at Las Campanas Observatory; three clusters at Cerro Tololo
Interamerican Observatory; and eight clusters at the Gemini Observatory.
Spectroscopic data were collected for only four galaxy clusters using Gemini
telescopes. With the photometry, the galaxies were defined based on the
star-galaxy separation taking into account photometric parameters. For each
galaxy cluster, the catalogues contain the PSF and aperture magnitudes of
galaxies within the 90\% completeness limit. They are used together with
structural parameters to study the galaxy morphology and to estimate
photometric redshifts. With the spectroscopy, the derived galaxy velocity
dispersion of our clusters ranged from 507 km~s$^{-1}$ for [VMF98]022 to 775
km~s$^{-1}$ for [VMF98]097 with signs of substructure. Cluster membership has
been extensively discussed taking into account spectroscopic and photometric
redshift estimates. In this sense, members are the galaxies within a projected
radius of 0.75 Mpc from the X-ray mission peak and with cluster centric
velocities smaller than the cluster velocity dispersion or 6000 km~s$^{-1}$,
respectively. These results will be used in forthcoming papers to study, among
the main topics, the red cluster sequence, blue cloud and green populations;
the galaxy luminosity function and cluster dynamics.
