# On the origin of Fanaroff-Riley classification of radio galaxies: Deceleration of supersonic radio lobes - Astrophysics > Astrophysics of Galaxies

On the origin of Fanaroff-Riley classification of radio galaxies: Deceleration of supersonic radio lobes - Astrophysics > Astrophysics of Galaxies - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Abstract: We argue that the origin of -FRI-FRI{-.1em}I dichotomy- the divisionbetween Fanaroff-Riley class I FRI with subsonic lobes and class I{-.1em}IFRI{-.1em}I radio sources with supersonic lobes is sharp in the radio-opticalluminosity plane Owen-White diagram - can be explained by the decelerationof advancing radio lobes. The deceleration is caused by the growth of theeffective cross-sectional area of radio lobes. We derive the condition in whichan initially supersonic lobe turns into a subsonic lobe, combining theram-pressure equilibrium between the hot spots and the ambient medium with therelation between -the hot spot radius- and -the linear size of radio sources-obtained from the radio observations. We find that the dividing line betweenthe supersonic lobes and subsonic ones is determined by the ratio of the jetpower $L { m j}$ to the number density of the ambient matter at the coreradius of the host galaxy $\bar{n} { m a}$. It is also found that there existsthe maximal ratio of $L { m j}-\bar{n} { m a}$ and its value resides in$L { m j}-\bar{n} { m a} { m max}\approx 10^{44-47} { m erg} { m s}^{-1}{ m cm}^{3}$, taking account of considerable uncertainties. This suggests thatthe maximal value $L { m j}-\bar{n} { m a} { m max}$ separates betweenFRIs and FRI{-.1em}Is.

Autor: Nozomu Kawakatu, Motoki Kino, Hiroshi Nagai

Fuente: https://arxiv.org/