Abstract
We analyze the relationship between star formation (SF), substructure, and
supercluster environment in a sample of 107 nearby galaxy clusters using data
from the Sloan Digital Sky Survey. Previous works have investigated the
relationships between SF and cluster substructure, and cluster substructure and
supercluster environment, but definitive conclusions relating all three of
these variables has remained elusive. We find an inverse relationship between
cluster SF fraction (f_SF) and supercluster environment density, calculated
using the galaxy luminosity density field at a smoothing length of 8 h^-1 Mpc
(D8). The slope of f_SF vs. D8 is -0.008 +/- 0.002. The f_SF of clusters
located in low-density large-scale environments, 0.244 +/- 0.011, is higher
than for clusters located in high-density supercluster cores, 0.202 +/- 0.014.
We also divide superclusters, according to their morphology, into filament- and
spider-type systems. The inverse relationship between cluster f_SF and
large-scale density is dominated by filament- rather than spider-type
superclusters. In high-density cores of superclusters, we find a higher f_SF in
spider-type superclusters, 0.229 +/- 0.016, than in filament-type
superclusters, 0.166 +/- 0.019. Using principal component analysis, we confirm
these results and the direct correlation between cluster substructure and SF.
These results indicate that cluster SF is affected by both the dynamical age of
the cluster (younger systems exhibit higher amounts of SF); the large-scale
density of the supercluster environment (high-density core regions exhibit
lower amounts of SF); and supercluster morphology (spider-type superclusters
exhibit higher amounts of SF at high densities).
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