The evolution of radio galaxies
The evolution of radio galaxies
Radio galaxies with extended lobes are believed to interact strongly with their environment. In this thesis, I investigate the evolution of radio galaxies with different properties and track them through the cosmological ages.
In Chapters 2 and 3, I perform a ”Monte-Carlo-based” population synthesis study which combines a model for the luminosity evolution of an individual FRII source with the radio luminosity function as a function of redshift. The artificial samples generated are then compared with complete observational samples. The results show that the properties of FRII sources are required to evolve with redshift. I also study the distribution of the jet properties as a function of redshift. From currently available data it is not possible to constrain the shape of the distribution of environment density or age, but jet power is found to follow a power-law distribution with an exponent of approximately -2. This power-law slope does not change with redshift out to z = 0.6. I also find the distribution of the pressure in the lobes of FRII sources to evolve with redshift up to z ~ 1.2.
FRI sources are not yet considered in Chapter 3, as existing analytical models for FRI soures are less successful. Thus in Chapters 4, I present a new analytical model for FRI jets. The model is based on a mixing-layer structure in which an initially laminar, relativistic flow is surrounded by a shear layer. I apply the appropriate conservation laws to constrain the jet parameters, starting the model where the radio emission is observed to brighten abruptly. Applying the model to a sample of the well-observed FRI sources, including example 3C 31, I find a self-consistent solution, from which I derive the jet power together with other properties like the entrainment rate.
The model in Chapter 4 leads an idea of estimating the maximum lengths and ages of the FR II sources by considering the entrainment process during their evolutions. In Chapter 5, I consider the laminar part of the jet may be destroyed due to the entrainment under certain assumpsions, in which case the radio outflows cease to be FR IIs after a few 108 yrs, at which point they have typically reached sizes of around 1 Mpc. Based on this idea, I then further discuss a plausible transition process from FRIIs into FRIs.
Wang, Yang
c56a6976-ef90-42bf-a8bc-9f227aa211bd
28 February 2010
Wang, Yang
c56a6976-ef90-42bf-a8bc-9f227aa211bd
Knigge, Christian
ac320eec-631a-426e-b2db-717c8bf7857e
Wang, Yang
(2010)
The evolution of radio galaxies.
University of Southampton, School of Physics and Astronomy, Doctoral Thesis, 155pp.
Record type:
Thesis
(Doctoral)
Abstract
Radio galaxies with extended lobes are believed to interact strongly with their environment. In this thesis, I investigate the evolution of radio galaxies with different properties and track them through the cosmological ages.
In Chapters 2 and 3, I perform a ”Monte-Carlo-based” population synthesis study which combines a model for the luminosity evolution of an individual FRII source with the radio luminosity function as a function of redshift. The artificial samples generated are then compared with complete observational samples. The results show that the properties of FRII sources are required to evolve with redshift. I also study the distribution of the jet properties as a function of redshift. From currently available data it is not possible to constrain the shape of the distribution of environment density or age, but jet power is found to follow a power-law distribution with an exponent of approximately -2. This power-law slope does not change with redshift out to z = 0.6. I also find the distribution of the pressure in the lobes of FRII sources to evolve with redshift up to z ~ 1.2.
FRI sources are not yet considered in Chapter 3, as existing analytical models for FRI soures are less successful. Thus in Chapters 4, I present a new analytical model for FRI jets. The model is based on a mixing-layer structure in which an initially laminar, relativistic flow is surrounded by a shear layer. I apply the appropriate conservation laws to constrain the jet parameters, starting the model where the radio emission is observed to brighten abruptly. Applying the model to a sample of the well-observed FRI sources, including example 3C 31, I find a self-consistent solution, from which I derive the jet power together with other properties like the entrainment rate.
The model in Chapter 4 leads an idea of estimating the maximum lengths and ages of the FR II sources by considering the entrainment process during their evolutions. In Chapter 5, I consider the laminar part of the jet may be destroyed due to the entrainment under certain assumpsions, in which case the radio outflows cease to be FR IIs after a few 108 yrs, at which point they have typically reached sizes of around 1 Mpc. Based on this idea, I then further discuss a plausible transition process from FRIIs into FRIs.
More information
Published date: 28 February 2010
Organisations:
University of Southampton
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Local EPrints ID: 161183
URI: http://eprints.soton.ac.uk/id/eprint/161183
PURE UUID: 4b8c2826-8760-4cb8-b781-977804989a5a
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Date deposited: 30 Jul 2010 11:37
Last modified: 14 Mar 2024 01:59
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Author:
Yang Wang
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