Far-infrared emission from intergalactic medium in Stephan's Quintet revealed by AKARI

TL;DR

This study uses AKARI observations to detect and analyze far-infrared emission from the intergalactic medium in Stephan's Quintet, revealing cold dust and shock-related emissions, and discussing their origins.

Contribution

First detection of intergalactic dust emission in Stephan's Quintet using AKARI's four-band far-infrared imaging.

Findings

Far-IR emission detected in the intergalactic medium of SQ.

Shock-powered [CII]158um emission contributes to 160 um band.

Cold dust temperature (~20 K) is lower than in surrounding galaxies.

Abstract

The Stephan's Quintet (SQ, HCG92) was observed with the Far-Infrared Surveyor (FIS) aboard AKARI in four far-infrared (IR) bands at 65, 90, 140, and 160 um. The AKARI four-band images of the SQ show far-IR emission in the intergalactic medium (IGM) of the SQ. In particular, the 160 um band image shows single peak emission in addition to the structure extending in the North-South direction along the shock ridge as seen in the 140 um band, H2 emission and X-ray emission. Whereas most of the far-IR emission in the shocked region comes from the cold dust component, shock-powered [CII]158um emission can significantly contribute to the emission in the 160 um band that shows a single peak at the shocked region. In the shocked region, the observed gas-to-dust mass ratio is in agreement with the Galactic one. The color temperature of the cold dust component (~20 K) is lower than that in surrounding galaxies (~30 K). We discuss a possible origin of the intergalactic dust emission.