Intrinsic Alignment in redMaPPer clusters -- II. Radial alignment of
  satellites toward cluster centers
  We study the orientations of satellite galaxies in redMaPPer clusters
constructed from the Sloan Digital Sky Survey at $0.1<z<0.35$ to determine
whether there is any preferential tendency for satellites to point radially
toward cluster centers. We analyze the satellite alignment (SA) signal based on
three shape measurement methods (re-Gaussianization, de Vaucouleurs, and
isophotal shapes), which trace galaxy light profiles at different radii. The
measured SA signal depends on these shape measurement methods. We detect the
strongest SA signal in isophotal shapes, followed by de Vaucouleurs shapes.
While no net SA signal is detected using re-Gaussianization shapes across the
entire sample, the observed SA signal reaches a statistically significant level
when limiting to a subsample of higher luminosity satellites. We further
investigate the impact of noise, systematics, and real physical isophotal
twisting effects in the comparison between the SA signal detected via different
shape measurement methods. Unlike previous studies, which only consider the
dependence of SA on a few parameters, here we explore a total of 17 galaxy and
cluster properties, using a statistical model averaging technique to naturally
account for parameter correlations and identify significant SA predictors. We
find that the measured SA signal is strongest for satellites with the following
characteristics: higher luminosity, smaller distance to the cluster center,
rounder in shape, higher bulge fraction, and distributed preferentially along
the major axis directions of their centrals. Finally, we provide physical
explanations for the identified dependences, and discuss the connection to
theories of SA.
