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LOFAR detected the last echo of Virgo A

Submitter: Emanuela Orru
Description: Using early phase LOFAR data, a team of radio astronomers involved in the commissioning of the International LOFAR Telescope (ILT) produced one of the best images ever made of Virgo A, the giant bubbles produced by the super-massive black hole at the center of the Virgo cluster.
The result is of great importance both from the scientific and technical point of view. It provides compelling evidence of the strong interaction between the galaxy's super-massive black hole and the galaxy's surroundings. Similar to symbiotic species, with the galaxy providing matter to feed the black hole, and the black hole returning energy to the galaxy.

From the technical point of view, Virgo A is one of the most difficult radio sources to image with high dynamic range at low frequencies. The reason is that Virgo A is at relatively low declination and the morphology of the source is a blend of compact emission at high brightness and extended emission at low brightness. We would not have expected to get such high quality results so early in the commissioning phase of LOFAR.
The image above represents two bands: optical in white/blue and radio in yellow/orange. The radio emission originates at the centre of the galaxy M87 that one can see as a white shaded area in the central part of the image. The extremely bright white area in the centre instead is due to very high surface brightness radio emission where the jet emanating from the super-massive black hole is located.

The radio data are a LOFAR HBA image at 140 MHz. The rms noise level is 20 mJy/beam, the peak flux is 101 Jy/beam and the resolution is 21 X 15 arcsec
Copyright: de Gasperin, Orru, Murgia & LOFAR collaboration 2012
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