Remnant radio-loud AGN in the Herschel-ATLAS field
2018
Only a small fraction of observed active galactic nuclei (AGN) display large-scale radio emission associated with jets, yet these radio-
loudAGN have become increasingly important in models of galaxy evolution. In determining the dynamics and energetics of the radio sources over
cosmic time, a key question concerns what happens when their jets switch off. The resulting ‘remnant' radio-
loudAGN have been surprisingly evasive in past radio surveys, and therefore statistical information on the population of radio-
loudAGN in their dying phase is limited. In this paper, with the recent developments of Low-Frequency Array (
LOFAR) and the Very Large Array, we are able to provide a systematically selected sample of remnant radio-
loudAGN in the Herschel-ATLAS field. Using a simple core-detection method, we constrain the upper limit on the fraction of remnants in our radio-
loudAGN sample to 9 per cent, implying that the extended lobe emission fades rapidly once the core/jets turn off. We also find that our remnant sample has a wide range of spectral indices (−1.5 ⩽ α 1400 150 ⩽ −0.5), confirming that the lobes of some remnants may possess flat spectra at low frequencies just as active sources do. We suggest that, even with the unprecedented sensitivity of
LOFAR, our sample may still only contain the youngest of the remnant population.
Keywords:
-
Correction
-
Source
-
Cite
-
Save
85
References
54
Citations
NaN
KQI