| Description: | Low-frequency radio emission allows powerful active galactic nuclei (AGN) to be selected in a way that is unaffected by dust obscuration and orientation of the jet axis. It also reveals past activity (e.g. radio lobes) that may not be evident at higher frequencies. Currently, there are too few ‘radio-loud’ galaxies for robust, detailed studies in terms of redshift-evolution and/or environment. Hence our use of observations from the Murchison Widefield Array -- a precursor telescope for the Square Kilometre Array -- to construct the GLEAM 4-Jy (G4Jy) Sample (1,863 sources at S_151MHz > 4.0 Jy; White et al. 2020a, 2020b). This sample is dominated by AGN and is over 10 times larger than the heavily relied-upon 3CRR sample (173 sources at S_178MHz > 10.9 Jy; Laing et al. 1983) of the northern hemisphere. In order to understand how AGN influence their surroundings and the way in which galaxies evolve, it is crucial to correctly identify the galaxy hosting the radio emission. This has been completed for the G4Jy Sample -- through repeated visual inspection and extensive checks against the literature -- forming a valuable, legacy dataset for investigating relativistic jets and their interplay with the environment. The first two papers detailing the sample are now on arXiv, and you can keep up-to-date by bookmarking the following repository: https://github.com/svw26/G4Jy . Note that 140 G4Jy sources have been observed using Open Time on MeerKAT (PI: White), and that 564 G4Jy sources lie within the footprint of the LOFAR Two-metre Sky Survey (Shimwell et al. 2017).
In this image, GLEAM contours (170-231 MHz; red), NVSS contours (1.4 GHz; blue), and TGSS contours (150 MHz; yellow) are overlaid onto a mid-infrared image from AllWISE (W1). Also plotted are positions from GLEAM (red squares), NVSS (blue crosses), TGSS (yellow diamonds), and 6dFGS (magenta diamonds). The white plusses indicate the host-galaxy positions (identified in the mid-infrared) for two G4Jy radio-sources. |
