2010A&A...514A...7G

We aim to reveal environmental dependence of infrared luminosity functions (IR LFs) of galaxies at z∼0.8 using the AKARI satellite. AKARI's wide field of view and unique mid-IR filters help us to construct restframe 8µm LFs directly without relying on SED models. We construct restframe 8µm IR LFs in the cluster region RXJ1716.4+6708 at z=0.81, and compare them with a blank field using the AKARI north ecliptic pole deep field data at the same redshift. AKARI's wide field of view (10'x10') is suitable to investigate wide range of galaxy environments. AKARI's 15µm filter is advantageous here since it directly probes restframe 8µm at z∼0.8, without relying on a large extrapolation based on a SED fit, which was the largest uncertainty in previous work. We have found that cluster IR LFs at restframe 8µm have a factor of 2.4 smaller L^* and a steeper faint-end slope than that of the field. Confirming this trend, we also found that faint-end slopes of the cluster LFs becomes flatter and flatter with decreasing local galaxy density. These changes in LFs cannot be explained by a simple infall of field galaxy population into a cluster. Physics that can preferentially suppress IR luminous galaxies in high density regions is required to explain the observed results.