Probing the Outskirts of the Early Stage Galaxy Cluster Merger A1750
  We present results from recent Suzaku and Chandra X-ray, and MMT optical
observations of the strongly merging "double cluster" A1750 out to its virial
radius, both along and perpendicular to a putative large-scale structure
filament. Some previous studies of individual clusters have found evidence for
ICM entropy profiles that flatten at large cluster radii, as compared with the
self-similar prediction based on purely gravitational models of hierarchical
cluster formation, and gas fractions that rise above the mean cosmic value.
Weakening accretion shocks and the presence of unresolved cool gas clumps, both
of which are expected to correlate with large scale structure filaments, have
been invoked to explain these results. In the outskirts of A1750, we find
entropy profiles that are consistent with self-similar expectations, and gas
fractions that are consistent with the mean cosmic value, both along and
perpendicular to the putative large scale filament. Thus, we find no evidence
for gas clumping in the outskirts of A1750, in either direction. This may
indicate that gas clumping is less common in lower temperature (kT~4keV), less
massive systems, consistent with some (but not all) previous studies of low
mass clusters and groups. Cluster mass may therefore play a more important role
in gas clumping than dynamical state. Finally, we find evidence for diffuse,
cool (<1 keV) gas at large cluster radii (R200) along the filament, which is
consistent with the expected properties of the denser, hotter phase of the
WHIM.
