Increased Prevalence of Bent Lobes for Double-Lobed Radio Galaxies in
  Dense Environments
  Double-lobed radio galaxies (DLRGs) often have radio lobes which subtend an
angle of less than 180 degrees, and these bent DLRGs have been shown to
associate preferentially with galaxy clusters and groups. In this study, we
utilize a catalog of DLRGs in SDSS quasars with radio lobes visible in VLA
FIRST 20 cm radio data. We cross-match this catalog against three catalogs of
galaxies over the redshift range $0 < z < 0.70$, obtaining 81 tentative
matches. We visually examine each match and apply a number of selection
criteria, eventually obtaining a sample of 44 securely detected DLRGs which are
paired to a nearby massive galaxy, galaxy group, or galaxy cluster. Most of the
DLRGs identified in this manner are not central galaxies in the systems to
which they are matched. Using this sample, we quantify the projected density of
these matches as a function of projected separation from the central galaxy,
finding a very steep decrease in matches as the impact parameter increases (for
$\Sigma \propto b^{-m}$ we find $m = 2.5^{+0.4}_{-0.3}$) out to $b \sim 2$ Mpc.
In addition, we show that the fraction of DLRGs with bent lobes also decreases
with radius, so that if we exclude DLRGs associated with the central galaxy in
the system the bent fraction is 78\% within 1 Mpc and 56\% within 2 Mpc,
compared to just 29\% in the field; these differences are significant at
$3.6\sigma$ and $2.8\sigma$ respectively. This behavior is consistent with ram
pressure being the mechanism that causes the lobes to bend.
