A dynamical model for FR II type radio sources with terminated jet activity

Abstract

Context. The extension of the KDA analytical model of FR II−type source evolution originally assuming a continuum injection process in the jet−IGM (intergalactic medium) interaction towards a case of the jet's termination is presented and briefly discussed. Aims. The dynamical evolution of FR II−type sources predicted with this extended model, hereafter referred to as KDA EXT, and its application to the chosen radio sources. Methods. Following the classical approach based on the source's continuous injection and self-similarity, I propose the effective formulae describing the length and luminosity evolution of the lobes during an absence of the jet flow, and present the resulting diagrams for the characteristics mentioned. Results. Using an algorithm based on the numerical integration of a modified formula for jet power, the KDA EXT model is fitted to three radio galaxies. Their predicted spectra are then compared to the observed spectra, proving that these fits are better than the best spectral fit provided by the original KDA model of the FR II−type sources dynamical evolution.

Reassessment of an Origin of the Radio Structure of J1420–0545

“…However, the very large size and uncommon propagation speed of J1420−0545 (resulting from its relatively young age determined from the model) testify against a dense environment. The analysis of Kuligowska (2017) shows how much the radio spectrum will steepen in relation to its initial slope when a period of quiescence is comparable to the lifetime of the jet activity, even if α inj is not very high.…”

“…Komissarov & Gubanov 1994;Murgia et al 2011). For this reason, an extension of the DYNAGE code (the dynamical model with terminated jet activity, KDA EXT), described by Kuligowska (2017), was applied. The extension of the DYNAGE code is based on the division of the cocoon's temporal evolution into two periods: the time of the jet activity until its termination (t j ) and that from the terminated activity until the actual age of the source, t. The evolution during the first period is described in detail in Machalski et al (2007).…”

“…The extension of the DYNAGE code is based on the division of the cocoon's temporal evolution into two periods: the time of the jet activity until its termination (t j ) and that from the terminated activity until the actual age of the source, t. The evolution during the first period is described in detail in Machalski et al (2007). A further evolution after t j , proposed by Kuligowska (2017), relying on modified expressions for the adiabatic expansion of the cocoon, its pressure, and integrated radio power, is summarized in the Appendix. In the first step of the modeling, we repeated the calculations of MJSK using the new data for the narrow lobes (the entries in column 5 of Table 2), and realized that the earlier models for the "Primary" or "Inner" origin of the structure are not changed appreciably.…”

Studying the highly bent spectra of FR II-type radio galaxies with the KDA EXT model

“…Among them are both very weak radio relics (Shulevski et al 2015) and objects with so-called recurrent activity (Saikia A&A proofs: manuscript no. 31535_corr & Jamrozy 2010), as well as the more typical, powerful radio galaxies with curved spectra (i.e., the ones modeled and discussed by Kuligowska (2017). It is worth emphasising that the problem of evolution of FR II-type sources after their jet activity has stopped was previously widely discussed by Kaiser & Cotter (2002).…”

“…However, their statistical test suggests that the KDA model still appears to provide better results than the Manolakou & Kirk and Blundell et al models. The KDA EXT model originally published by Kuligowska (2017) arose from the need to better understand the processes occurring in FR II−type radio sources after the end of their nuclear activity. In contrast to the previously developed models describing the dynamics of these sources and based on the "standard model", such as KDA, BRW and MK, KDA EXT was constructed on the assumption of the lack of so-called continuous injection (hereafter CI) of new particles into the lobes at the time at which the given source is observed.…”