|Submitter:||Volker Heesen, Judith Croston, Raffaella Morganti|
|Description:|| LOFAR was from the beginning expected to provide beautiful images of the diffuse and faint radio emission in radio galaxies. And indeed, it has kept this promise! In the image above, the red, twisting structure shows the radio emission traced by LOFAR at 145 MHz of a famous and well-studied radio galaxy known as 3C31. This is superposed to an optical image (white objects which trace regions with stars) of the field. Straightaway, one can see the huge extent of the radio emission compared to the optical size. |
The new LOFAR 145-MHz map shows that 3C 31 has a larger physical size than previously known, reaching 1.1 Mpc (4 million light-years!). This means 3C31 now falls in the class of giant radio galaxies.
However, the 145-MHz LOFAR image is not only beautiful, but also very useful for understanding how such huge objects like 3C31 evolve. To do this, the LOFAR HBA image has been combined with LOFAR LBA data (60 MHz) and with observations by other radio telescopes (VLA, GMRT and WSRT). The analysis revealed that the plasma flow in the jets must decelerate while expanding into the intergalactic medium. This would suggest an age of the radio galaxy of about 190 Myr, implying supersonic expansion of the tails of plasma.
The results are presented in Heesen, V. et al. 2017 “ LOFAR reveals the giant: a low-frequency radio continuum study of the outflow in the nearby FR I radio galaxy 3C 31”, published in Monthly Notices of the Royal Astronomical Society and available on https://arxiv.org/abs/1710.09746