Modelling the broad-band spectra of X-ray emitting GPS galaxies

The study of the broad-band emission of GHz-Peaked-Spectrum (GPS) radio galaxies is a powerful tool to investigate the physical processes taking place in the central, kpc-sized region of their active hosts, where the jets propagate and the lobes expand, interacting with the surrounding interstellar medium (ISM). We recently developed a new dynamical-radiative model to describe the evolution of the GPS phenomenon (Stawarz et al. 2008): as the relativistic jets propagate through the ISM, gradually engulfing narrow-line emitting gas clouds along their way, the electron population of the expanding lobes evolves, emitting synchrotron light, as well as inverse-Compton radiation via up-scattering of the photon fields from the host galaxy and its active nucleus. The model, which successfully reproduces the key features of the GPS radio sources as a class, provides a description of the evolution of their spectral energy distribution (SED) with the lobes' expansion, predicting significant and complex X-ray to gamma-ray emission. We apply here the model to the broad-band SED's of a sample of known, X-ray emitting GPS galaxies, and show that: (i) the free-free absorption mechanism enables us to reproduce the radio continuum at frequencies below the turnover; (ii) the lobes' non-thermal, inverse-Compton emission can account for the observed X-ray spectra, providing a viable alternative to the thermal, accretion-dominated scenario. We also show that, in our sample, the relationship between the X-ray and radio hydrogen column densitities, N_H and N_HI, is suggestive of a positive correlation, which, if confirmed, would support the scenario of high-energy emitting lobes.Comment: 4 pages, 2 figures, accepted for publication in Astronomische Nachrichten (issue dedicated to the Proceedings of "The Fourth Workshop on Compact Steep Spectrum and GHz-Peaked Spectrum Radio Sources"

The inflation experience of older households

Recent increases in inflation have been accompanied by concerns over the extent to which official figures match the 'true' household experience of inflation. Rapid increases in the prices of household fuel, petrol and diesel and, more recently, of food have brought considerable attention to the fact that inflation will be different for different households according to their expenditure patterns. Any measure of inflation, such as the Retail Prices Index (RPI) or Consumer Prices Index (CPI), is necessarily only an average of the experience of different households and may not be especially representative of what is happening for any household in particular. Using data from the Expenditure and Food Survey, this Commentary looks at the inflation experience (based on the RPI) for different groups of households, examining how the average inflation rate they face has varied over time and making comparisons across the groups, focusing in particular on pensioner households

The expenditure experience of older households

This commentary examines detailed trends in expenditure patterns between 1995 and 2007, with a particular focus on the pensioner population. Pensioners are not a homogeneous group, but differ widely in both their levels and patterns of spending, and so we look not just at pensioners as a whole but also at pensioners according to age, income, household composition and so on. Spending may tell us something about household welfare that other, often-used measures like incomes do not. In particular, it may be that spending is informative about long-run well-being whereas income is more about current, short-run living standards. Using data from the Family Expenditure Survey/Expenditure and Food Survey, an annual, cross-sectional study of the spending patterns of 6,000-7,000 households, we look in depth at changes in the level of real expenditures and how spending patterns have changed over time. Then, using data from two waves of the English Longitudinal Study of Ageing, we examine household fuel expenditures in detail. Fuel is clearly of great current policy concern given recent large increases in the price of domestic fuel that may impact particularly severely on poorer and older households

A survey of the UK benefit system

This paper describes all the main benefits in the UK system, giving details of rates and allowances, as well as numbers and types of claimants and levels of expenditure

Optical spectroscopy of faint gigahertz peaked spectrum sources

We present spectroscopic observations of a sample of faint Gigahertz Peaked Spectrum (GPS) radio sources drawn from the Westerbork Northern Sky Survey (WENSS). Redshifts have been determined for 19 (40%) of the objects. The optical spectra of the GPS sources identified with low redshift galaxies show deep stellar absorption features. This confirms previous suggestions that their optical light is not significantly contaminated by AGN-related emission, but is dominated by a population of old (>9 Gyr) and metal-rich (>0.2 [Fe/H]) stars, justifying the use of these (probably) young radio sources as probes of galaxy evolution. The optical spectra of GPS sources identified with quasars are indistinguishable from those of flat spectrum quasars, and clearly different from the spectra of Compact Steep Spectrum (CSS) quasars. The redshift distribution of the GPS quasars in our radio-faint sample is comparable to that of the bright samples presented in the literature, peaking at z ~ 2-3. It is unlikely that a significant population of low redshift GPS quasars is missed due to selection effects in our sample. We therefore claim that there is a genuine difference between the redshift distributions of GPS galaxies and quasars, which, because it is present in both the radio-faint and bright samples, can not be due to a redshift-luminosity degeneracy. It is therefore unlikely that the GPS quasars and galaxies are unified by orientation, unless the quasar opening angle is a strong function of redshift. We suggest that the GPS quasars and galaxies are unrelated populations and just happen to have identical observed radio-spectral properties, and hypothesise that GPS quasars are a sub-class of flat spectrum quasars.Comment: LaTeX, 13 pages. Accepted by MNRAS. For related papers see http://www.ast.cam.ac.uk/~snelle

Household consumption through recent recessions

This paper examines trends in household consumption and saving behaviour in each of the last three recessions in the UK. We identify several dimensions along which the most recent recession (the so-called 'Great Recession') has been different from those that occurred in the 1980s and 1990s. These include its depth and length as well as the composition of the cutbacks in expenditure - with a greater reliance on cuts to nondurable expenditure than was seen in previous recessions. We show that, both inside and outside recessions, the extent to which the growth in durable purchases is more volatile than growth in nondurable purchases has declined over the past 15 years. Finally, we present evidence that suggests that two aspects of fiscal policy in the UK in 2008 and 2009 - the temporary reduction in the rate of VAT and a car scrappage scheme - had some success in encouraging households to bring forward some durable purchases.

The living standards of families with children reporting low incomes

The Government has high-profile child poverty targets which are assessed using a measure of income, as recorded in the Household Below Average Income series (HBAI). However, income is an imperfect measure of living standards. Previous analysis suggests that some children in households with low income do not have commensurately low living standards. This report aims to document the extent to which this is true, focusing on whether children in low-income households have different living standards depending on whether their parents are employed, self-employed, or workless

Structure, spectra and variability of some GPS radio sources

We report the results of multifrequency-VLBI observations of GHz-Peaked-Spectrum (GPS) radio sources. The VLBI structure and component spectra of some GPS sources are presented. Our VLBI results show that about 80% of the GPS galaxies exhibit a compact double or CSO-like structure, while the GPS quasars tend to show a core-jet. The component spectra of the GPS galaxies are often steep/convex, and the core has a flat spectrum but it is usually hidden or weak. In addition, we studied the variability of GPS sources by comparing new flux density measures, acquired with the Urumqi 25m telescope at 4.85 GHz, with previous 87GB data. The results show that 44% of the GPS quasars varied higher than 10% in passed 20 years, while the fraction is only 12% for the GPS galaxies meaning that the GPS quasars are much more variable than GPS galaxies. In total, 25% of GPS sources show >10% variability at 4.85 GHz in our sample.Comment: 4 pages, 7 figure