Discovery of "Warm Dust" Galaxies in Clusters at z~0.3: Evidence for
  Stripping of Cool Dust in the Dense Environment?
  Using far-infrared imaging from the "Herschel Lensing Survey", we derive dust
properties of spectroscopically-confirmed cluster member galaxies within two
massive systems at z~0.3: the merging Bullet Cluster and the more relaxed
MS2137.3-2353. Most star-forming cluster sources (~90%) have characteristic
dust temperatures similar to local field galaxies of comparable infrared (IR)
luminosity (T_dust ~ 30K). Several sub-LIRG (L_IR < 10^11 L_sun) Bullet Cluster
members are much warmer (T_dust > 37K) with far-infrared spectral energy
distribution (SED) shapes resembling LIRG-type local templates. X-ray and
mid-infrared data suggest that obscured active galactic nuclei do not
contribute significantly to the infrared flux of these "warm dust" galaxies.
Sources of comparable IR-luminosity and dust temperature are not observed in
the relaxed cluster MS2137, although the significance is too low to speculate
on an origin involving recent cluster merging. "Warm dust" galaxies are,
however, statistically rarer in field samples (> 3sigma), indicating that the
responsible mechanism may relate to the dense environment. The spatial
distribution of these sources is similar to the whole far-infrared bright
population, i.e. preferentially located in the cluster periphery, although the
galaxy hosts tend towards lower stellar masses (M_* < 10^10 M_sun). We propose
dust stripping and heating processes which could be responsible for the
unusually warm characteristic dust temperatures. A normal star-forming galaxy
would need 30-50% of its dust removed (preferentially stripped from the outer
reaches, where dust is typically cooler) to recover a SED similar to a "warm
dust" galaxy. These progenitors would not require a higher IR-luminosity or
dust mass than the currently observed normal star-forming population.
