We present the results of our mid-infrared (MIR) observations of distant clusters of galaxies with AKARI. The wide-eld of view of IRC/AKARI (10'X10') is ideally suited for studying dust-obscured star-formation (SF) activity of galaxies along the cosmic web in the distant universe. We performed a deep and wide-field 15 μm (rest-frame  8 μm) imaging observation of the RXJ1716+6708 cluster (z = 0:81) with IRC. We find that 15 m-detected cluster member galaxies (with total infrared luminosities of LIR & 1011L⊙) are most preferentially located in the cluster outskirt regions, whilst such IR-luminous galaxies avoid the cluster centre. Our Hα follow-up study of this field conrmed that a significant fraction of 15 μm-detected cluster galaxies are heavily obscured by dust (with AHα>3 mag in extreme cases). The environment of such dusty star-burst galaxies coincides with the place where we see a sharp "break" of the colour-density relation, suggesting an important link between dust-obscured SF activity and environmental quenching. We also report the discovery of a new cluster candidate around a radio galaxy at z = 1:52 (4C 65.22), where we obtained one of the deepest IRC imaging datasets with all the nine filters at 2-24 μm. This field will provide us with the final, excellent laboratory for studying the dust-enshrouded SF activity in galaxies along the cosmic web at the critical epoch of cluster galaxy evolution with AKARI.

ABSTRACT
1. INTRODUCTION
2. PANORAMIC MIR VIEW OF A z=0.8 CLUSTER
3. A NEWLY DISCOVERED RICH CLUSTER AT z=1.5
4. SUMMARY & FUTURE
REFERENCES

• Yusei Koyama(Institute of Space Astronomical Science, Japan Aerospace Exploration Agency)