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Goto, T.; Koyama, Y.; Wada, T.; Pearson, C.; Matsuhara, H.; Takagi, T.; Shim, H.; Im, M.; Lee, M. G.; Inami, H.; Malkan, M.; Okamura, S.; Takeuchi, T. T.; Serjeant, S.; Kodama, T.; Nakagawa, T.; Oyabu, S.; Ohyama, Y.; Lee, H. M.; Hwang, N.; Hanami, H.; Imai, K. and Ishigaki, T.
(2010).
DOI: https://doi.org/10.1051/0004-6361/200913473
Abstract
Aims. 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 8 μm LFs directly without relying on SED models.
Methods. We construct restframe 8 μm 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' × 10') is suitable to investigate wide range of galaxy environments. AKARI's 15 μm filter is advantageous here since it directly probes restframe 8 μm at z ~ 0.8, without relying on a large extrapolation based on a SED fit, which was the largest uncertainty in previous work.
Results. We have found that cluster IR LFs at restframe 8 μm 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.
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