The Herschel Virgo Cluster Survey: VI. The far-infrared view of M87

TL;DR

This study uses Herschel observations to determine that the far-infrared emission from M87 is entirely due to synchrotron radiation, with no evidence of dust emission, challenging previous claims.

Contribution

It provides the first comprehensive Herschel-based analysis showing that M87's far-infrared emission is synchrotron-dominated, negating the need for a dust component.

Findings

Far-infrared emission is explained by synchrotron radiation.

No evidence of diffuse dust component in M87.

Supports the idea that the environment affects dust presence in radio galaxies.

Abstract

The origin of the far-infrared emission from the nearby radio galaxy M87 remains a matter of debate. Some studies find evidence of a far-infrared excess due to thermal dust emission, whereas others propose that the far-infrared emission can be explained by synchrotron emission without the need for an additional dust emission component. We present Herschel PACS and SPIRE observations of M87, taken as part of the science demonstration phase observations of the Herschel Virgo Cluster Survey. We compare these data with a synchrotron model based on mid-infrared, far-infrared, submm and radio data from the literature to investigate the origin of the far-infrared emission. Both the integrated SED and the Herschel surface brightness maps are adequately explained by synchrotron emission. At odds with previous claims, we find no evidence of a diffuse dust component in M87, which is not unexpected in the harsh X-ray environment of this radio galaxy sitting at the core of the Virgo Cluster.