Tuesday

I will present radio, optical and infrared data on a new 2.5 Mpc giant radio galaxy (GRG), which is associated with a disturbed galaxy group. This new GRG spans an enormous 40 arc minutes on the sky (larger than a full moon), and was discovered in the LOFAR survey; the Multifrequency Snapshot Sky Survey (MSSS). GRGs are rare and old objects which represent the final stage in the evolution of radio sources. They can only grow in low density environments but require significant fuelling of a central supermassive black hole to grow the Mpc-sized radio lobes.

This GRG is associated with a small galaxy group, within which one is identified as a broad-line galaxy in the Sloan Digital Sky Survey (SDSS) at a redshift of 0.054. Given it is nearby, it is an ideal object to study the details behind radio loud AGN over Myear timescales, and its interaction with the warm-hot intergalactic medium. Analysis of the infrared data suggests that the host is a lenticular type galaxy with a large stellar mass (log M/Mo = 11.56 +/- 0.12), and a moderate star formation rate (1.2 +/- 0.4 Mo /year). Spatially smoothing the SDSS images shows the galaxy group to be significantly disturbed, with a prominent extension to the south-east. Overall, the evidence suggests the host galaxy has undergone one or more recent moderate merger events and is also experiencing tidal interactions with surrounding galaxies, which have caused the star formation and provided the supply of gas to trigger and fuel the AGN over the large time-scales needed to produce Mpc radio lobes.

Followup deep observations with LOFAR have revealed the detailed and curious morphology of the lobes from arc-second to arc-minute scales. In essence this GRG has three lobes associated with it, where one lobe has bifurcated into two, possibly due to the jet being disrupted by the inter-galactic medium. Furthermore, the new LOFAR data has provided direct evidence that the galaxy and its AGN have moved 30 kpc over the lifetime of the GRG (with a direction in agreement with the disturbed tail from SDSS maps), giving an age estimate of around 100 Myears.