International comparison of light rail operations with reference to urban population density patterns

The experience of urban light rail in Europe offers sharp contrasts. The German and French experience has placed light rail or tram at the centre of attempts to revitalise city centres using attractive modern forms of new public%0D transport infrastructure. British experience has been based on a closer focus on value for money and tighter limits to subsidy, at both the infrastructure and operation stage. With this policy contrast as a background, this paper reports on an international research project which used GIS techniques to map light rail routes and local population density patterns for a selection of case study cities. It addresses issues such as whether specific modern tram systems such as the Sheffield Supertram was handicapped by decisions over its routing%2C together with the scale of international differences in local population densities and their impact on accessibility of the population to the light rail system. The project made use of local authority data from German, French, and British cities, plus analysis using MapInfo GIS software.

The Rank-Size Rule in Europe - testing Zipf’s law using European data

The large literature on the rank-size rule of city sizes has received rather inconsistent treatment in the European continent. Part of the problem has been the fact that (unlike the U.S.) there are inconsistent Census dates and no uniform definition of what is meant by an urban area. This paper uses data from a French research project which provides physical urban area data for a number of (not all) European countries, down to quite small minimum urban sizes. This allows international comparison of the usual Pareto estimation parameters, and also some examination of whether square or cubic terms are significant. The nature and economic basis of such non-linearities in the logarithmic rank-size relationship are of interest. The spatial nature of the urban size hierarchy has also been rather neglected recently, and much research in this area has virtually ignored the location of the cities, focusing solely on size. Appropriate treatment of nearby urban centres is a tricky empirical problem, as is the proper treatment of urban areas spreading across two or more countries. One of the main background economic motives for studying urban size hierarchies in Europe is to speculate on whether the development of the Eurozone may lead to movement towards a U.S.- type size distribution, which follows the rank-size rule rather well.

Impact on Car Ownership of Local Variation in Access to Public Transport

This paper reports on a project funded by the Volvo Research Foundations. It is international in nature and focuses on the impact of urban public transport, and light rail in particular, on restraining the growth of (or even reducing) local car ownership rates. The recent Censuses of the UK (2001) and France (1999) make these two countries particularly suitable, but the project examined other countries and urban transport systems too. We were especially interested in the `high quality' alternatives to light rail, including other urban rail, or enhanced forms of bus. Especially in Britain, the investment costs in new light rail systems have led to Government disquiet and reluctance to approve funding. The empirical work consists of econometric estimates using small area data, mainly from Censuses, reinforced by GIS mapping of urban transport access on the local small area. 300 metre and 600 metre zones of good access can then be used in the econometrics, alongside socioeconomic indicators of the economically active population. Results from a wide range of cities suggest that good access does indeed reduce car ownership below what would be expected given the local socioeconomic profile. These findings have important implications for environmental and transport policy

Urban unemployment in the EU, tertiary sector employment growth and urban size

The paper uses REGIO data to study recent change in unemployment in major urban areas of Europe. Previous results suggested a significant role for tertiarisation in employment, and a systematic association with urban size. This work is carried forward using more recent data on urban areas at NUTS3 level. Patterns in variation of unemployment across countries and city sizes are discussed. Econometric estimates going beyond OLS are discussed using LIMDEP software. Details on long term unemployment are only available at NUTS2 level, but this still provides useful insight for the largest EU urban areas for which the NUTS2 region is a useful approximation to the urban area. Some policy implications are also discussed, in the light of the recent debate over `Euro-sclerosis' in the labour market.

Two close large quasar groups of size ∼ 350 Mpc at

The Clowes & Campusano large quasar group (LQG) at inline image has been re-examined using the quasar data from the DR7QSO catalogue of the Sloan Digital Sky Survey. In the 1991 discovery, the LQG impinged on the northern, southern and eastern limits of the survey. In the DR7QSO data, the western, northern and southern boundaries of the LQG remain essentially the same, but an extension eastwards of ∼2° is indicated. In the DR7QSO data, the LQG has 34 members, with inline image. A new group of 38 members is indicated at inline image and within ∼2bsl000640 of the Clowes & Campusano LQG. The characteristic sizes of these two LQGs, ∼350–400 Mpc, appear to be only marginally consistent with the scale of homogeneity in the concordance cosmology. In addition to their intrinsic interest, these two LQGs provide locations in which to investigate early large-scale structure in galaxies and to identify high-z clusters. A method is presented for assessing the statistical significance and overdensity of groups found by linkage of points

A Relationship between Supermassive Black Hole Mass and the Total Gravitational Mass of the Host Galaxy

We investigate the correlation between the mass of a central supermassive black hole and the total gravitational mass of the host galaxy (M_tot). The results are based on 43 galaxy-scale strong gravitational lenses from the Sloan Lens ACS (SLACS) Survey whose black hole masses were estimated through two scaling relations: the relation between black hole mass and Sersic index (M_bh - n) and the relation between black hole mass and stellar velocity dispersion (M_bh - sigma). We use the enclosed mass within R_200, the radius within which the density profile of the early type galaxy exceeds the critical density of the Universe by a factor of 200, determined by gravitational lens models fitted to HST imaging data, as a tracer of the total gravitational mass. The best fit correlation, where M_bh is determined from M_bh - sigma relation, is log(M_bh) = (8.18 +/- 0.11) + (1.55 +/- 0.31) (log(M_tot) - 13.0) over 2 orders of magnitude in M_bh. From a variety of tests, we find that we cannot reliably infer a connection between M_bh and M_tot from the M_bh - n relation. The M_bh - M_tot relation provides some of the first, direct observational evidence to test the prediction that supermassive black hole properties are determined by the halo properties of the host galaxy.Comment: 29 pages, 10 figures, Accepted for publication in Ap

A structure in the early Universe at z 1.3 that exceeds the homogeneity scale of the R-W concordance cosmology

A Large Quasar Group (LQG) of particularly large size and high membership has been identified in the DR7QSO catalogue of the Sloan Digital Sky Survey. It has characteristic size (volume^1/3) ~ 500 Mpc (proper size, present epoch), longest dimension ~ 1240 Mpc, membership of 73 quasars, and mean redshift = 1.27. In terms of both size and membership it is the most extreme LQG found in the DR7QSO catalogue for the redshift range 1.0 = 1.28, which is itself one of the more extreme examples. Their boundaries approach to within ~ 2 deg (~ 140 Mpc projected). This new, huge LQG appears to be the largest structure currently known in the early universe. Its size suggests incompatibility with the Yadav et al. scale of homogeneity for the concordance cosmology, and thus challenges the assumption of the cosmological principle

Characterizing the Adaptive Optics Off-Axis Point-Spread Function - I: A Semi-Empirical Method for Use in Natural-Guide-Star Observations

Even though the technology of adaptive optics (AO) is rapidly maturing, calibration of the resulting images remains a major challenge. The AO point-spread function (PSF) changes quickly both in time and position on the sky. In a typical observation the star used for guiding will be separated from the scientific target by 10" to 30". This is sufficient separation to render images of the guide star by themselves nearly useless in characterizing the PSF at the off-axis target position. A semi-empirical technique is described that improves the determination of the AO off-axis PSF. The method uses calibration images of dense star fields to determine the change in PSF with field position. It then uses this information to correct contemporaneous images of the guide star to produce a PSF that is more accurate for both the target position and the time of a scientific observation. We report on tests of the method using natural-guide-star AO systems on the Canada-France-Hawaii Telescope and Lick Observatory Shane Telescope, augmented by simple atmospheric computer simulations. At 25" off-axis, predicting the PSF full width at half maximum using only information about the guide star results in an error of 60%. Using an image of a dense star field lowers this error to 33%, and our method, which also folds in information about the on-axis PSF, further decreases the error to 19%.Comment: 29 pages, 9 figures, accepted for publication in the PAS