Galaxy Clusters at 0.9<z<1.7 in the AKARI NEP deep field
Abstract
There is a huge gap between properties of red-sequence selected massive galaxy clusters at z<1 and Lyman-break selected proto-clusters at z>3. It is important to understand when and how the z>3 proto-clusters evolve into passive clusters at z<1. We aim to fill this cluster desert by using the space-based N4(4um) imaging with the AKARI. The z'-N4 color is a powerful separator of cluster galaxies at z>1, taking advantage of the 4000A break and the 1.6um bump. We carefully selected 16 promising cluster candidates at 0.9<z<1.7, which all show obvious over-density of galaxies and a prominent red-sequence. At this redshift range, the mid-infrared S15um/S9um flux ratio is an extinction-free indicator of galaxy star formation activity due to the redshifted PAH emission lines (6.2,7.7 and 8.6um). We show statistically that the cluster galaxies have a lower S15um/S9um flux ratio than field galaxies, i.e., cluster galaxies already have lower star-formation activity at 0.9<z<1.7, pushing the formation epoch of these galaxy clusters to a higher redshift.
Cite
@article{arxiv.0810.0529,
title = {Galaxy Clusters at 0.9<z<1.7 in the AKARI NEP deep field},
author = {Tomotsugu Goto and Hitoshi Hanami and Myungshin Im and Koji Imai and Hanae Inami and Tsuyoshi Ishigaki and Hyung Mok Lee and Hideo Matsuhara and Takao Nakagawa and Youichi Ohyama and Shinki Oyabu and Chris P. Pearson and Toshinobu Takagi and Takehiko Wada},
journal= {arXiv preprint arXiv:0810.0529},
year = {2017}
}
Comments
Accepted for publication in PASJ AKARI special issue. Full-resolution version available at http://ifa.hawaii.edu/~tomo/research/out/akari_cluster_v10.pdf Typos fixed