We have used narrow emission‐line data from the new 7C Redshift Survey to investigate correlations between the narrow‐line luminosities and the radio properties of radio galaxies and steep‐spectrum quasars. The 7C Redshift Survey is a low‐frequency (151 MHz) selected sample with a flux density limit about 25 times fainter than the 3CRR sample. By combining these samples, we can for the first time distinguish whether the correlations present are controlled by 151‐MHz radio luminosity L151 or redshift z. We find unequivocal evidence that the dominant effect is a strong positive correlation between narrow‐line luminosity LNLR and L151, of the form . Correlations of LNLR with redshift or radio properties, such as linear size or 151‐MHz (rest frame) spectral index, are either much weaker or absent. We use simple assumptions to estimate the total bulk kinetic power Q of the jets in FR II radio sources, and confirm the underlying proportionality between jet power and narrow‐line luminosity first discussed by Rawlings & Saunders. We make the assumption that the main energy input to the narrow‐line region is photoionization by the quasar accretion disc, and relate Q to the disc luminosity, Qphot. We find that 0.05≲QQphot≲1, so that the jet power is within about an order of magnitude of the accretion disc luminosity. Values of QQphot∼1 require the volume filling factor η of the synchrotron‐emitting material to be of the order of unity, and in addition require one or more of the following: (i) an important contribution to the energy budget from protons; (ii) a large reservoir of mildly relativistic electrons; and (iii) a substantial departure from the minimum‐energy condition in the lobe material. The most powerful radio sources are accreting at rates close to the Eddington limit of supermassive black holes (MBH≳109 M⊙), whilst lower power sources are accreting at sub‐Eddington rates.

We describe the inter-dependence of four properties of classical double radio sources -spectral index, linear size, luminosity and redshift -from an extensive study based on spectroscopicallyidentified complete samples. We use these relationships to discuss aspects of strategies for searching for radio galaxies at extreme redshifts, in the context of possible capabilities of the new generation of proposed radio telescopes.

We present K-band imaging of all 49 radio galaxies in the 7C-I and 7C-II regions of the 7C Redshift Survey (7CRS). The low-frequency (151-MHz) selected 7CRS sample contains all sources with flux densities S 151 > 0.5 Jy in three regions of the sky. We combine the K-band magnitudes of the 7CRS radio galaxies with those from the 3CRR, 6CE and 6C samples to investigate the nature of the relationship between K-magnitude and redshift and whether there is any dependence upon radio luminosity. We find that radio galaxies appear to belong to a homogeneous population that formed the bulk of their stars at high redshifts (z f > 5) and evolved passively from then until they reach a mean present-day luminosity of 3 L . We find a significant difference between the K-magnitudes of the 7CRS and 3CRR radio galaxies with the 7CRS galaxies being ≈0.55 mag fainter at all redshifts. The cause of this weak correlation between stellar and radio luminosities probably lies in mutual correlations of these properties with the central black hole mass. We compare the evolution-corrected host luminosities at a constant radio luminosity and find that the typical host luminosity (mass) increases by approximately 1 L from z ∼ 2 to ∼0.5 which, although a much smaller factor than predicted by semi-analytic models of galaxy formation, is in line with results on optically selected quasars. Our study has therefore revealed that the small dispersion in stellar luminosity of radio galaxies around 3 L includes subtle but significant differences between the host galaxies of extreme-and moderate-power radio sources at fixed redshift, and between those of high-and low-redshift radio sources at fixed radio luminosity.

We measure the radio luminosity function (RLF) of steep‐spectrum radio sources using three redshift surveys of flux‐limited samples selected at low (151 and 178 MHz) radio frequency, low‐frequency source counts and the local RLF. The redshift surveys used are the new 7C Redshift Survey (7CRS) and the brighter 3CRR and 6CE surveys totalling 356 sources with virtually complete redshift z information. This yields unprecedented coverage of the radio luminosity versus z plane for steep‐spectrum sources, and hence the most accurate measurements of the steep‐spectrum RLF yet made. We find that a simple dual‐population model for the RLF fits the data well, requiring differential density evolution (with z) for the two populations. The low‐luminosity population can be associated with radio galaxies with weak emission lines, and includes sources with both FRI and FRII radio structures; its comoving space density ρ rises by about one dex between z∼0 and 1 but cannot yet be meaningfully constrained at higher redshifts. The high‐luminosity population can be associated with radio galaxies and quasars with strong emission lines, and consists almost exclusively of sources with FRII radio structure; its ρ rises by nearly three dex between z∼0 and 2. These results mirror the situation seen in X‐ray and optically selected samples of AGN where: (i) low‐luminosity objects exhibit a gradual rise in ρ with z that crudely matches the rises seen in the rates of global star formation and galaxy mergers; and (ii) the density of high‐luminosity objects rises much more dramatically. The integrated radio luminosity density of the combination of the two populations is controlled by the value of ρ at the low‐luminosity end of the RLF of the high‐luminosity population, a quantity which has been directly measured at z∼1 by the 7CRS. We argue that robust determination of this quantity at higher redshifts requires a new redshift survey based on a large (∼1000 source) sample about five times fainter than the 7CRS.

An understanding of thermal physics is crucial to much of modern physics, chemistry, and engineering. This book provides a modern introduction to the main principles that are foundational to thermal physics, thermodynamics, and statistical mechanics. The key concepts are carefully presented in a clear way, and new ideas are illustrated with worked examples as well as a description of the historical background to their discovery. Applications are presented to subjects as diverse as stellar astrophysics, information and communication theory, condensed matter physics, and climate change. Each chapter concludes with detailed exercises. This second edition of the text maintains the structure and style of the first edition but extends its coverage of thermodynamics and statistical mechanics to include several new topics, including osmosis, diffusion problems, Bayes theorem, radiative transfer, the Ising model, and Monte Carlo methods. New examples and exercises have been added throughout.

The so-called "stationary" Hα line of SS433 is shown to consist of three components. A broad component is identified as emitted in that wind from the accretion disc which grows in speed with elevation above the plane of the disc. There are two narrow components, one permanently redshifted and the other permanently to the blue. These are remarkably steady in wavelength and must be emitted from a circumbinary ring, orbiting the centre of mass of the system rather than orbiting either the compact object or its companion: perhaps the inner rim of an excretion disc. The orbiting speed (approximately 200 km s −1 ) of this ring material strongly favours a large mass for the enclosed system (around 40 M ⊙ ), a large mass ratio for SS433, a mass for the compact object plus accretion disc of ∼ 16 M ⊙ and hence the identity of the compact object as a rather massive stellar black hole.

We compare two temporal properties of classical double radio sources: i) radiative lifetimes of synchrotron-emitting particles and ii) dynamical source ages. We discuss how these can be quite discrepant from one another, rendering use of the traditional spectral ageing method inappropriate: we contend that spectral ages give meaningful estimates of dynamical ages only when these ages are ≪ 10 7 years. In juxtaposing the fleeting radiative lifetimes with source ages which are significantly longer, a refinement of the paradigm for radio source evolution is required. We move beyond the traditional bulk backflow picture and consider alternative means of the transport of high Lorentz factor (γ) particles, which are particularly relevant within the lobes of low luminosity classical double radio sources. The changing spectra along lobes are explained, not predominantly by synchrotron ageing but, by gentle gradients in a magnetic field mediated by a low-γ matrix which illuminates an energy-distribution of particles, N (γ), controlled largely by classical synchrotron loss in the high magnetic field of the hotspot. A model of magnetic field whose strength lowers with increasing distance from the hotspot, and in so doing becomes increasingly different from the equipartition value in the head of the lobe, is substantiated by constraints from different types of inverse-Compton scattered X-rays. The energy in the particles is an order of magnitude higher than that inferred from the minimum-energy estimate, implying that the jet-power is of the same order as the accretion luminosity produced by the quasar central engine. This refined paradigm points to a resolution of the findings of Rudnick et al (1994) and that both the Jaffe-Perola and Kardashev-Pacholczyk model spectra are invariably poor descriptions of the curved spectral shape of lobe emission, and indeed that for Cygnus A all regions of the lobes are characterised by a 'universal spectrum'.

High‐resolution X‐ray and low‐frequency radio imaging now allow us to examine in detail the interaction and physical properties of the radio source 3C 84 and the surrounding thermal gas. The radiative and dynamical properties of the inner X‐ray holes, which coincide with the radio lobes, indicate that the ratio of the energy factor k to the filling factor f is in the range 180