Vol. 547
In section 4. Extragalactic astronomy

M87 at metre wavelengths: the LOFAR picture

by F. de Gasperin, E. Orru, M. Murgia, A. Merloni, et al., A&A 547, A56


This is the first image of M87 provided by LOFAR at low radio frequencies, which were never explored before at these high spatial resolution and dynamic range. M87 is the biggest elliptical galaxy at the center of the Virgo cluster. It has an active nucleus (AGN) with a supermassive black hole of mass 6.4 10^9 M_sun, and its radio jets have produced 80 kpc-long radio lobes. From these multi-wavelength observations, a low-frequency spectral index map is derived, and a best-fit model is proposed based on a continuous injection of relativistic electrons, meaning that the AGN continues to supply fresh relativistic particles to the radio lobes. The map does not reveal new extended emission, but the source appears to be well-confined by the high pressure of the intra-cluster medium.