A WISE View of a Nearby Supercluster A2199
  We use Wide-field Infrared Survey Explorer (WISE) data covering the entire region (~130 deg^2) of the A2199 supercluster at z=0.03 to study the mid-infrared (MIR) properties of supercluster galaxies. We identify a `MIR star-forming sequence' in the WISE [3.4]-[12] color-12 \mu m luminosity diagram, consisting of late-type, star-forming galaxies. At a fixed star formation rate (SFR), the MIR-detected galaxies at 22 \mu m or 12 \mu m tend to be more metal rich and to have higher surface brightness than those without MIR detection. Using these MIR-detected galaxies, we construct the IR luminosity function (LF) and investigate its environmental dependence. Both total IR (TIR) and 12 \mu m LFs are dominated by late-type, star-forming galaxies. The contribution of active galactic nuclei (AGN)-host galaxies increases with both TIR and 12 \mu m luminosities. The contribution of early-type galaxies to the 12 \mu m LFs increases with decreasing luminosity. The faint-end slope of the TIR LFs does not change with environment, but the change of faint-end slope in the 12 \mu m LFs with the environment is significant: there is a steeper faint-end slope in the cluster core than in the cluster outskirts. This steepening results primarily from the increasing contribution of early-type galaxies toward the cluster. These galaxies are passively evolving, and contain old stellar populations with weak MIR emission from the circumstellar dust around asymptotic giant branch stars. 
Ho Seong Hwang (1), Margaret J. Geller (1), Antonaldo Diaferio (2,3),   Kenneth J. Rines (4) ((1) SAO, (2) Universita` di To...
astro-ph.CO