A simulation-based analytic model of radio galaxies - new paper by Martin Hardcastle
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by
JeanTate
Link to abstract (arXiv:1801.00667); abstract:
I derive and discuss a simple semi-analytical model of the evolution of powerful radio galaxies which is not based on assumptions of self-similar growth, but rather implements some insights about the dynamics and energetics of these systems derived from numerical simulations, and can be applied to arbitrary pressure/density profiles of the host environment. The model can qualitatively and quantitatively reproduce the source dynamics and synchrotron light curves derived from numerical modelling. Approximate corrections for radiative and adiabatic losses allow it to predict the evolution of radio spectral index and of inverse-Compton emission both for active sources and for `remnant' sources after the jet has turned off. Code to implement the model is publicly available. Using a standard model with a light relativistic (electron-positron) jet, sub-equipartition magnetic fields, and a range of realistic group/cluster environments, I simulate populations of sources and show that the model can reproduce the range of properties of powerful radio sources as well as observed trends in the relationship between jet power and radio luminosity, and predicts their dependence on redshift and environment. I show that the distribution of source lifetimes has a significant effect on both the source length distribution and the fraction of remnant sources expected in observations, and so can in principle be constrained by observations. The remnant fraction is expected to be low even at low redshift and low observing frequency due to the rapid luminosity evolution of remnants, and to tend rapidly to zero at high redshift due to inverse-Compton losses.
There's no direct relation to what we, volunteers, do (at least, not that I can see); however, a great many of the radio sources we classify show - to varying degrees of clarity - just how unrealistic some (many?) of the assumptions that go into the "simple semi-analytical model" are. And it might be fun to discuss this; for example, what do the many #asym sources say about which assumptions?
One part of the paper I found particularly cool: Martin creates 10k simulated sources, for two time-evolution scenarios, from his model, then puts them into a (simulated) evolving universe, and extracts what they would look like, through the eyes of an ideal, contemporary radio observatory.
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