8 research outputs found
Constraints on the energetics and plasma composition of relativistic jets in FR II sources
We explore the energetics and plasma composition in FR II sources using a new
simple method of combining shock dynamics and radiation spectrum. The hot spots
are identified with the reverse shocked region of jets. With the
one-dimensional shock jump conditions taking account of the finite pressure of
hot ICM, we estimate the rest mass and energy densities of the sum of thermal
and non-thermal particles in hot spots. Independently, based on the Synchrotron
Self-Compton (SSC) model, we estimate the number and energy densities of {\it
non-thermal} electrons using the multi-frequency radiation spectrum of hot
spots. We impose the condition that the obtained rest mass, internal energy,
and number densities of non-thermal electrons should be lower than those of the
total particles determined by shock dynamics. We apply this method to Cygnus A.
We examine three extreme cases of pure electron-positron pair plasma (Case I),
pure electron-proton plasma with separate thermalization (Case II), and pure
electron-proton plasma in thermal-equilibrium (Case III). By detailed SSC
analysis for Cygnus A and 3C123, we find that the energy density of non-thermal
electrons is about 10 times larger than that of magnetic field. We find that
the Case III is not acceptable because predicted photon spectra do not give a
good fit to the observed one. We find that Case II can also be ruled out since
the number density of non-thermal electrons exceeds that of the total number
density. Hence, we find that only pure plasma (Case I) is acceptable
among the three cases. Total kinetic power of jet and electron acceleration
efficiency are also constrained by internal energy densities of non-thermal and
total particles.Comment: 12 pages, 9 figures, accepted to MNRA
Particle acceleration in relativistic outows
In this review we confront the current theoretical understanding of particle
acceleration at relativistic outflows with recent observational results on
various source classes thought to involve such outflows, e.g. gamma-ray bursts,
active galactic nuclei, and pulsar wind nebulae. We highlight the possible
contributions of these sources to ultra-high-energy cosmic rays.Comment: Accepted for publication in Space Science Reviews, will also appear
as chapter of an ISSI publicatio