  We aim to use multi-band imaging from the Phase-3 Verification Data of the
J-PLUS survey to derive accurate photometric redshifts (photo-z) and look for
potential new members in the surroundings of the nearby galaxy clusters A2589
(z=0.0414) & A2593 (z=0.0440), using redshift probability distribution
functions. The ultimate goal is to demonstrate the usefulness of a 12-band
filter system in the study of large-scale structure in the local universe. We
present an optimized pipeline for the estimation of photo-z in clusters of
galaxies. We tested our photo-z with a sample of 296 spectroscopically
confirmed cluster members with a magnitude of <r>= 16.6 and redshift <z>=0.041.
The combination of seven narrow and five broadband filters with a typical
photometric-depth of r<21.5 provides dz/(1+z)=0.01 photo-z estimates. A
precision of dz/(1+z)=0.005 is obtained for the 177 galaxies brighter than
magnitude r<17. To foresee the precision beyond the spectroscopic sample, we
designed a set of simulations in which real cluster galaxies are modeled and
reinjected inside the images at different signal-to-noise. A precision of
dz/(1+z)=0.02 and dz/(1+z)=0.03 is expected at <r>= 18-22, respectively.
Complementarily, we used SDSS/DR12 data to derive photo-z estimates for the
same galaxy sample, demonstrating that the wavelength-resolution of the J-PLUS
can double the precision achieved by SDSS for galaxies with a high S/N. We find
as much as 170 new candidates across the entire field. The spatial distribution
of these galaxies may suggest an overlap between the systems with no evidence
of a clear filamentary structure connecting the clusters. These preliminary
results show the potential of J-PLUS data to revisit membership of groups and
clusters from nearby galaxies, important for the determination of luminosity
and mass functions and environmental studies at the intermediate and low-mass
regime.
