Environmental dependence of polycyclic aromatic hydrocarbon emission at z~0.8. Investigation by observing the RX J0152.7-1357 with AKARI

TL;DR

This study investigates how the environment influences PAH emission in galaxies at z~0.8, finding that environment affects galaxy types but not the PAH emission behavior of star-forming galaxies.

Contribution

It provides observational evidence that environment impacts galaxy type distribution but not the PAH emission properties of star-forming galaxies at intermediate redshift.

Findings

No clear difference in L8/LIR between field and cluster galaxies.

Starburst galaxies are only found in the outskirts of the cluster.

L8/LIR behavior of star-forming galaxies is consistent across environments.

Abstract

We study the environmental dependence of the strength of polycyclic aromatic hydrocarbon (PAH) emission by AKARI observations of RX J0152.7-1357, a galaxy cluster at z=0.84. PAH emission reflects the physical conditions of galaxies and dominates 8 um luminosity (L8), which can directly be measured with the L15 band of AKARI. L8 to infrared luminosity (LIR) ratio is used as a tracer of the PAH strength. Both photometric and spectroscopic redshifts are applied to identify the cluster members. The L15-band-detected galaxies tend to reside in the outskirt of the cluster and have optically green colour, R-z'~ 1.2. We find no clear difference of the L8/LIR behaviour of galaxies in field and cluster environment. The L8/LIR of cluster galaxies decreases with specific-star-formation rate divided by that of main-sequence galaxies, and with LIR, consistent with the results for field galaxies. The relation between L8/LIR and LIR is between those at z=0 and z=2 in the literature. Our data also shows that starburst galaxies, which have lower L8/LIR than main-sequence, are located only in the outskirt of the cluster. All these findings extend previous studies, indicating that environment affects only the fraction of galaxy types and does not affect the L8/LIR behaviour of star-forming galaxies.