Synchrotron self-absorption in the GPS radio galaxy B0108+388

Abstract

Context. The compact radio source in the nucleus of the GPS radio galaxy B0108+388 consists of two jets that have spectra that turn over at frequecies lower than ∼5 GHz. There is evidence that the spectral turnover in B0108+388 results from free-free absorption by non-uniform thermal plasma in central tens of parsecs. Aims. To reveal the real cause of the low frequency cutoff in the jet spectra, it is necessary to consider different mechanisms and, in particular, syncrotron self-absorption. Methods. We suggest that spectral turnovers at low frequencies of the jets are caused by synchrotron self-absorption. Estimations of physical parameters of these jets were obtained with a method based on a non-uniform synchrotron source model. Results. We find that magnetic fields in these jets are nearly uniform with 10 −2 < H ⊥ < 10 −1 G and with relativistic electron density 10 1 < n e < 10 2 cm −3 . The relativistic electron energy is higher everywhere in the jets than the magnetic field energy, but by taking the estimated uncertainties into account it is possible that energy equipartition is in effect. We compare the physical conditions in the jets and in the nuclei of classical doubles. Conclusions. We present evidence that the spectral turnover in the B0108+388 results from synchrotron self-absorption.

Chang-Es V: Nuclear Outflow in a Virgo Cluster Spiral After a Tidal Disruption Event

“…We note that a magnetic field as large as B(−2) = 10 (e.g. Artyukh et al 2008) would reduce the required U o to a more reasonable 3 − 4%, but this would still have to be removed by an inhomogeneous, depolarizing screen to satisfy our limit. Finally we calculate Stokes Q in the same approximation and limit.…”

“…For ν 5 = 1 (a spectral turnover of 5 GHz, Fig. 6), for fields even as large as 0.04 G (a comfortable upper limit, see Artyukh et al 2008) the lifetime of particles radiating at the spectral turnover is about 58 years and γ e = 173. Higher energy particles by about a factor of one hundred would be evolving substantially.…”

“…For synchrotron self-absorption (SSA) as an explanation for a GPS source (see e.g. Artyukh et al 2008) one expects the brightness temperature of the source to approach the electron kinetic temperature (e.g. Longair 1994).…”

The spectral turnover-linear size relation and the dynamical evolution of compact steep spectrum sources

“…Ubachukwu, Okoye & Onuora 1991, and references therein). Assuming lobe confinement by ram‐pressure balance with the external medium, then we have (Ubachukwu et al 1991; Fanti et al 1995; Readhead et al 1996; Carvalho 1998; Artyukh, Chernikov & Tyul'bashev 2008; Labiano 2008; Orienti & Dallacasa 2008) where P i is lobe internal pressure, n e is external medium density and m H is proton mass. Using , it can be shown that the kinetic power, P cj , delivered by the core to the jet can be expressed according to the following relation (see also Carvalho 1998): where Ω is jet opening solid angle and c is light speed.…”

“…Ubachukwu, Okoye & Onuora 1991, and references therein). Assuming lobe confinement by ram-pressure balance with the external medium, then we have (Ubachukwu et al 1991;Fanti et al 1995;Readhead et al 1996;Carvalho 1998;Artyukh, Chernikov & Tyul'bashev 2008;Labiano 2008;Orienti & Dallacasa 2008)…”