Gravitational lensing by elliptical galaxies

The fraction of high-redshift sources which are multiply-imaged by intervening galaxies is strongly dependent on the cosmological constant, and so can be a useful probe of the cosmological model. However its power is limited by various systematic (and random) uncertainties in the calculation of lensing probabilities, one of the most important of which is the dynamical normalisation of elliptical galaxies. Assuming ellipticals' mass distributions can be modelled as isothermal spheres, the mass normalisation depends on: the velocity anisotropy; the luminosity density; the core radius; and the area over which the velocity dispersion is measured. The differences in the lensing probability and optical depth produced by using the correct normalisation can be comparable to the differences between even the most extreme cosmological models. The existing data is not sufficient to determine the correct normalisation with enough certainty to allow lensing statistics to be used to their full potential. However, as the correct lensing probability is almost certainly higher than is usually assumed, upper bounds on the cosmological constant are not weakened by these possibilities.Comment: MNRAS, in press; 13 pages, 22 figure

Gravitational lensing in galaxy redshift surveys

Gravitationally-lensed quasars should be discovered as a by-product of large galaxy redshift surveys, being discovered spectroscopically when a low-redshift galaxy exhibits high-redshift quasar emission lines. The number of lenses expected is higher than previously estimated, mainly due to the fact that the presence of the quasar images brings faint deflector galaxies above the survey limit. Thus the a posteriori likelihood of the discovery of Q 2237+0305 in the Center for Astrophysics redshift survey is approximately 0.03. In the future, the 2 degree Field survey should yield at least 10 lensed quasars, and the Sloan Digitial Sky Survey up to 100.Comment: Gravitational Lensing: Recent Progress and Future Goals, C.S. Kochanek & T.G. Brainerd, eds., in press; 2 pages, 1 figur

Using the 2dF galaxy redshift survey to detect gravitationally-lensed quasars

Galaxy redshift surveys can be used to detect gravitationally-lensed quasars if the spectra obtained are searched for the quasars' emission lines. Previous investigations of this possibility have used simple models to show that the 2 degree Field (2dF) redshift survey could yield several tens of new lenses, and that the larger Sloan Digital Sky Survey should contain an order of magnitude more. However the particular selection effects of the samples were not included in these calculations, limiting the robustness of the predictions; thus a more detailed simulation of the 2dF survey was undertaken here. The use of an isophotal magnitude limit reduces both the depth of the sample and the expected number of lenses, but more important is the Automatic Plate Measuring survey's star-galaxy separation algorithm, used to generate the 2dF input catalogue. It is found that most quasar lenses are classed as merged stars, with only the few lenses with low-redshift deflectors likely to be classified as galaxies. Explicit inclusion of these selection effects implies that the 2dF survey should contain 10 lenses on average. The largest remaining uncertainty is the lack of knowledge of the ease with which any underlying quasars can be extracted from the survey spectra.Comment: MNRAS, in press; 14 pages, 19 figure

Young people's participation in the development of a self-care intervention--a multi-site formative research study.

The poor outcomes of young people with chronic health conditions indicate that current services and self-care programmes are not meeting the needs of young people. How young people self-manage their condition impacts on long-term health outcomes, but there is little published evidence that details the development of self-care programmes and their most effective components. This article reports on an innovative formative research study, the purpose of which was to develop a self-care intervention prototype. Participants were 87 young people, aged 12-17, and seven young adult facilitators, aged 18-25, with type 1 diabetes or asthma. Each contributed to talking groups exploring themes that young people wanted to be addressed within a self-care programme. Instead of being focused on 'illness', young people's main concerns were directed toward 'life as an adolescent', while at the same time building sustainable daily routines of self-care. Overall, this article illustrates the process of initiating and implementing a developmental approach focused on young people, while also demonstrating the tailored self-care intervention that the process developed. This approach can be used to involve young people in the design and development of other conditions that rely on self-care interventions

Application of the Contouring Method to Extended Microlensed Sources

The method devised by Lewis et al. (1993) for calculating the light curve of a microlensed point source is expanded to two dimensions to enable the calculation of light curves of extended sources. This method is significantly faster than the ray shooting method that has been used in the past. The increased efficiency is used to obtain much higher resolution light curves over increased timescales. We investigate the signatures arising from different source geometries in a realistic microlensing model. We show that a large fraction of high magnification events (HMEs) in image A of Q2237+0305 involve only one caustic, and could therefore yield information on the structure of the quasar continuum through the recognition of a characteristic event shape. In addition, the cataloguing of HMEs into morphological type will, in theory, enable the direction of the transverse motion, as well as the source size to be obtained from long term monitoring.Comment: 10 pages including 4 figures. Accepted for publication in M.N.R.A.

Host Galaxy Contribution to the Colours of `Red' Quasars

We describe an algorithm that measures self-consistently the relative galaxy contribution in a sample of radio-quasars from their optical spectra alone. This is based on a spectral fitting method which uses the size of the characteristic 4000\AA~ feature of elliptical galaxy SEDs. We apply this method to the Parkes Half-Jansky Flat Spectrum sample of Drinkwater et al. (1997) to determine whether emission from the host galaxy can significantly contribute to the very red optical-to-near-infrared colours observed. We find that at around $2\sigma$ confidence, most of the reddening in unresolved (mostly quasar-like) sources is unlikely to be due to contamination by a red stellar component.Comment: 11 pages, 11 figures. Accepted for Publication in Monthly Notices of the Royal Astronomical Societ

Describing results of 4000 hours of multi environment model verification test Final report

Investigating categorization and formulation of stress and strength factors for semiconductor diodes to provide improved failure rate prediction from mathematical model

Interpretation of Solar Magnetic Field Strength Observations

This study based on longitudinal Zeeman effect magnetograms and spectral line scans investigates the dependence of solar surface magnetic fields on the spectral line used and the way the line is sampled in order to estimate the magnetic flux emerging above the solar atmosphere and penetrating to the corona from magnetograms of the Mt. Wilson 150-foot tower synoptic program (MWO). We have compared the synoptic program \lambda5250\AA line of Fe I to the line of Fe I at \lambda5233\AA since this latter line has a broad shape with a profile that is nearly linear over a large portion of its wings. The present study uses five pairs of sampling points on the $\lambda5233$\AA line. We recommend adoption of the field determined with a line bisector method with a sampling point as close as possible to the line core as the best estimate of the emergent photospheric flux. The combination of the line profile measurements and the cross-correlation of fields measured simultaneously with \lambda5250\AA and \lambda5233\AA yields a formula for the scale factor 1/\delta that multiplies the MWO synoptic magnetic fields. The new calibration shows that magnetic fields measured by the MDI system on the SOHO spacecraft are equal to 0.619+/-0.018 times the true value at a center-to-limb position 30 deg. Berger and Lites (2003) found this factor to be 0.64+/-0.013 based on a comparison the the Advanced Stokes Polarimeter.Comment: Accepted by Solar Physic