* Astronomy

Title: A WISE View of a Nearby Supercluster A2199
Authors: Ho Seong Hwang (1), Margaret J. Geller (1), Antonaldo Diaferio (2,3), Kenneth J. Rines (4) ((1) SAO, (2) Universita' di Torino, (3) INFN Torino, (4) WWU)

We use Wide-field Infrared Survey Explorer (WISE) data covering the entire region (~130 deg²) 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] colour-12 µm luminosity diagram, consisting of late-type, star-forming galaxies. At a fixed star formation rate (SFR), the MIR-detected galaxies at 22 µm or 12 µm 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 µm LFs are dominated by late-type, star-forming galaxies. The contribution of active galactic nuclei (AGN)-host galaxies increases with both TIR and 12 µm luminosities. The contribution of early-type galaxies to the 12 µm 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 µm 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.

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Google earth file: Abell 2199.kmz (4kb, kmz)