Identification of filamentary structures in the environment of
  superclusters of galaxies in the Local Universe
  The characterization of the internal structure of the superclusters of
galaxies (walls, filaments and knots where the clusters are located) is
paramount for understanding the formation of the Large Scale Structure and for
outlining the environment where galaxies evolved in the last Gyr. (i) To detect
the compact regions of high relative density (clusters and rich groups of
galaxies); (ii) to map the elongated structures of low relative density
(filaments, bridges and tendrils of galaxies); (iii) to characterize the galaxy
populations on filaments and study the environmental effects they are subject
to. We employed optical galaxies with spectroscopic redshifts from the
SDSS-DR13 inside rectangular boxes encompassing the volumes of a sample of 46
superclusters of galaxies, up to z=0.15. Our methodology implements different
classical pattern recognition and machine learning techniques pipelined in the
Galaxy Systems-Finding algorithm and the Galaxy Filaments-Finding algorithm. We
detected in total 2,705 galaxy systems (clusters and groups, of which 159 are
new) and 144 galaxy filaments in the 46 superclusters of galaxies. The
filaments we detected have a density contrast above 3, with a mean value around
10, a radius of about 2.5 Mpc and lengths between 9 and 130 Mpc. Correlations
between the galaxy properties (mass, morphology and activity) and the
environment in which they reside (systems, filaments and the dispersed
component) suggest that galaxies closer to the skeleton of the filaments are
more massive by up to 25% compared to those in the dispersed component; 70 % of
the galaxies in the filament region present early type morphologies and the
fractions of active galaxies (both AGN and SF) seem to decrease as galaxies
approach the filament. These results suggest that preprocessing in large scale
filaments could have significant effects on galaxy evolution.
