Consistency between the radio and MIR faint source counts using the radio-MIR correlation

We show from the recent extrapolation of the radio-FIR correlation to the MIR that the 20 cm and 15 um differential source counts are likely to come from the same parent population.Comment: 2 pages, 2 figures, to appear in proceedings of 'Multi-wavelength AGN surveys', Cozumel, 200

Gambling and the use of credit: an individual and household level analysis

We explore the relationship between gambling and other forms of risk-taking behaviour, i.e. exposure to debt and the use of credit, at the individual and household level using representative pooled cross-section data drawn from the UK Expenditure and Food Surveys (EFS), 2001 to 2007. Gambling and the use of credit are shown to be positively correlated at the household level. While both the incidence and amount of gambling vary according to household income, the positive association between gambling and the use of credit is remarkably stable across household income. In addition to our household level analysis, we also explore the prevalence of intra-household gambling, which has attracted relatively limited attention in the existing literature. It is apparent that there is strong intra-household correlation in both gambling activity and in the use of credit, with somewhat stronger relationships in lower income households

Cross-correlation of the unresolved X-ray background with faint galaxies

At the faint end of the deepest X-ray surveys, a population of X-ray luminous galaxies is seen. In this paper, we present the results of a cross-correlation between the residual, unresolved X-ray photons in a very deep X-ray survey and the positions of faint galaxies, in order to examine the importance of these objects at even fainter flux levels. We measure a significant correlation on all angular scales up to ~1 arcmin. This signal could account for a significant fraction of the unresolved X-ray background, approximately 35 per cent if the clustering is similar to optically selected galaxies. However, the angular form of the correlation is seen to be qualitatively similar to that expected for clusters of galaxies and the X-ray emission could be associated with hot gas in clusters or with QSOs within galaxy clusters rather than emission from individual faint galaxies. The relative contribution from each of these possibilities cannot be determined with the current data.Comment: 7 pages LaTeX including 9 EPS figures. Uses mn.sty. Accepted for publication by MNRA

The discovery of very red counterparts to faint X-ray sources

We present deep K-band imaging at the positions of four very faint X-ray sources found in the UK ROSAT Deep Survey to have no optical counterpart brighter than R~23. Likely identifications are found within the ROSAT error circle in all four fields with R-K colours of between 3.2 +/- 0.4 and 6.4 +/- 0.6. From a consideration of the R-K colours and X-ray to optical luminosity ratios of the candidate identifications, we tentatively classify two of the X-ray sources as very distant (z ~ 1) clusters of galaxies, one as a narrow emission line galaxy and one as an obscured QSO.Comment: 7 pages, LaTeX, 7 figures (1 postscript file each). Uses mn.sty and epsf.sty. Accepted by MNRAS. For more information see http://www.astro.soton.ac.uk/~amn/UKdee

Intergenerational Analysis of Social Interaction and Social Skills: An Analysis of U.S. and U.K. Panel Data

A body of empirical evidence supports a positive relationship between educational attainment and social interaction. We build on this literature by exploring the relationship between the social interaction of parents and their offspring from an empirical perspective. Using two U.K. and U.S. panel data sets, we find robust evidence of intergenerational links between the social interaction of parents and their offspring supporting the existence of positive intergenerational effects in social interaction. These links exist after controlling for an extensive set of factors covering family background including income and wealth as well as attempting to control for issues related to reverse causality and endogeneity. Our empirical evidence indicates that higher levels of parental social interaction are associated with higher levels of child social interaction. Our findings indicate an important influence on this facet of children's human capital, namely social skills, with positive consequences expected for educational attainment

The epidemiology of golfrelated injuries in Australian amateur golfers - a multivariate analysis

Objective. To perform an epidemiological study in order to determine the golf-related injury locations, injury rates and possible risk factors for golf injury in amateur golfers across Australia. Method. A retrospective cross-sectional survey of Australian golf club members was used to collect data for the study. Chi-square testing was used to evaluate the association between golf injury and each possible risk factor at univariate level. All the possible risk factors were further examined in multivariate analysis using logistical regression. Results. There were 1 634 golfers included in the present study. Of these, 288 reported having had one or more golfrelated injuries in the previous year. The most common injury location was the lower back (25.3%), followed by the elbow (15.3%) and shoulder (9.4%). The most common injury mechanism was poor technique in execution of the golf swing (44.8%). Age, warm-up status, conditioning habits, wearing a golf glove/s and injury acquired in other sports / activities were significantly associated with risk of golf injury (p < 0.05). Equipment use such as type of golf club shaft used, type of shoes used and other factors studied were not statistically significant. Conclusion. The most injured sites identified in this study were the lower back, elbow and shoulder respectively. Risk of injury during golfing varied according to age group, warm-up status, conditioning habits, whether the player wore a golf glove/s, and whether the golfer had been injured in other activities. South African Journal of Sports Medicine Vol. 19 (1) 2007: pp. 12-1

X-ray variability of AGNs in the soft and the hard X-ray bands

We investigate the X-ray variability characteristics of hard X-ray selected AGNs (based on Swift/BAT data) in the soft X-ray band using the RXTE/ASM data. The uncertainties involved in the individual dwell measurements of ASM are critically examined and a method is developed to combine a large number of dwells with appropriate error propagation to derive long duration flux measurements (greater than 10 days). We also provide a general prescription to estimate the errors in variability derived from rms values from unequally spaced data. Though the derived variability for individual sources are not of very high significance, we find that, in general, the soft X-ray variability is higher than those in hard X-rays and the variability strengths decrease with energy for the diverse classes of AGN. We also examine the strength of variability as a function of the break time scale in the power density spectrum (derived from the estimated mass and bolometric luminosity of the sources) and find that the data are consistent with the idea of higher variability at time scales longer than the break time scale.Comment: 17 pages, 15 Postscript figures, 3 tables, accepted for publication in Ap

X-ray spectral variability of the Seyfert galaxy NGC 4051

We report on the X-ray spectral variability of the Seyfert 1 galaxy NGC 4051 observed with the Rossi X-ray Timing Explorer (RXTE) during a 1000 day period between May 1996 and March 1999. The spectra were obtained as part of monitoring observations and from two long observations using the RXTE Proportional Counter Array (PCA). During the monitoring period the 2-10 keV flux of NGC 4051 varied between 10E-12 and 7x 10E11 (cgs). We re-analysed RXTE PCA observations from a distinct low state in May 1998 using the latest background and detector response models. The RXTE and BeppoSAX observations of NGC 4051 during the low state show a very hard spectrum with a strong unresolved fluorescence line. This emission, probably due to reflection from a molecular torus, is likely to be constant over long time-scales and is therefore assumed as an underlying component at all flux states. By subtracting the torus component we are able to determine the spectral variability of the primary continuum. In the variable component we observe a strong anti-correlation of X-ray flux and spectral hardness in the PCA energy band. We show that the changes in hardness are caused by slope variability of the primary power law spectrum rather than by changing reflection or variable photoelectric absorption. The primary spectral index varies between Gamma=1.6 for the faintest states and Gamma=2.3 during the brightest states, at which level the spectral index approaches an asympotic value. We find that the response of the flux of the 6.4 keV iron fluorescence line to changes in the continuum flux depends on the timescale of the observation. The profile of the line is very broad and indicates an origin in the innermost regions of the accretion disk.Comment: accepted for publication in MNRA

Constraints on the distribution of absorption in the X-ray selected AGN population found in the 13H XMM-Newton/Chandra deep field

We present an analysis of the X-ray properties of sources detected in the 13H XMM-Newton deep (200ks) field. In order to constrain the absorbed AGN population, we use extensive Monte Carlo simulations to directly compare the X-ray colours of observed sources with those predicted by several model distributions. We have tested the simplest form of the AGN unified scheme, whereby the intrinsic XLF of absorbed AGN is set to be the same as that of their unabsorbed brethren, coupled with various model distributions of absorption. The best fitting of these models sets the fraction of AGN with absorbing column NH, proportional to (logNH)^8. We have also tested two extensions to the unified scheme: an evolving absorption scenario, and a luminosity dependent model distribution. Both of these provide poorer matches to the observed X-ray colour distributions than the best fitting simple unified model. We find that a luminosity dependent density evolution XLF reproduces poorly the 0.5-2 keV source counts seen in the 13H field. Field to field variations could be the cause of this disparity. Computing the simulated X-ray colours with a simple absorbed power-law + reflection spectral model is found to over-predict, by a factor of two, the fraction of hard sources that are completely absorbed below 0.5 keV, implying that an additional source of soft-band flux must be present for a number of the absorbed sources. Finally, we show that around 40% of the 13H sample are expected to be AGN with NH>10^22 cm^-2.Comment: 13 pages, 9 figures, Accepted for publication in MNRA

Implications of the X-ray Variability for the Mass of MCG-6-30-15

The bright Seyfert 1 galaxy \mcg shows large variability on a variety of time scales. We study the \aproxlt 3 day time scale variability using a set of simultaneous archival observations that were obtained from \rxte and the {\it Advanced Satellite for Cosmology and Astrophysics} (\asca). The \rxte\ observations span nearly $10^6$ sec and indicate that the X-ray Fourier Power Spectral Density has an rms variability of 16%, is flat from approximately 10^{-6} - 10^{-5} Hz, and then steepens into a power law $\propto f^{-\alpha}$ with \alpha\aproxgt 1. A further steepening to $\alpha \approx 2$ occurs between 10^{-4}-10^{-3} Hz. The shape and rms amplitude are comparable to what has been observed in \ngc and \cyg, albeit with break frequencies that differ by a factor of 10^{-2} and 10^{4}, respectively. If the break frequencies are indicative of the central black hole mass, then this mass may be as low as $10^6 {\rm M}_\odot$. An upper limit of $\sim 2$ ks for the relative lag between the 0.5-2 keV \asca band compared to the 8-15 keV \rxte band was also found. Again by analogy with \ngc and \cyg, this limit is consistent with a relatively low central black hole mass.Comment: 5 pages, 3 figures, LaTeX, uses emulateapj.sty and apjfonts.sty, revised version, accepted for publication in ApJ Letter