Constraints on the Intracluster Dust Emission in the Coma Cluster of Galaxies

Abstract

We have undertaken a search for the infrared emission from the intracluster dust in the Coma cluster of galaxies by the Multiband Imaging Photometer for Spitzer. Our observations yield the deepest mid and far-infrared images of a galaxy cluster ever achieved. In each of the three bands, we have not detected a signature of the central excess component in contrast to the previous report on the detection by Infrared Space Observatory (ISO). We still find that the brightness ratio between 70 μm and 160 μm shows a marginal sign of the central excess, in qualitative agreement with the ISO result. Our analysis suggests that the excess ratio is more likely due to faint infrared sources lying on fluctuating cirrus foreground. Our observations yield the 2σ upper limits on the excess emission within 100 kpc of the cluster center as 5 × 10^-3 MJy sr^-1, 6 × 10^-2 MJy sr^-1, and 7 × 10^-2 MJy sr^-1, at 24, 70, and 160 μm, respectively. These values are in agreement with those found in other galaxy clusters and suggest that dust is deficient near the cluster center by more than 3 orders of magnitude compared with the interstellar medium.