Dynamical virial masses of Lyman-break galaxy haloes at z=3

We improve on our earlier dynamical estimate of the virial masses of the haloes of Lyman-break galaxies (LBGs) at redshift z=3 by accounting for the effects of seeing, slit width, and observational uncertainties. From an analysis of the small number of available rotation curves for LBGs we determine a relation Vc7=(1.9+/-0.2)sigma between circular velocity at a radius of 7kpc, and central line velocity width. We use this relation to transform the measured velocity widths of 32 LBGs to the distribution of circular velocities, for the population of LBGs brighter than R=25.5. We compare this distribution against the predicted distribution for the 'massive-halo' model in which LBGs pinpoint all of the highest mass dark matter haloes at that epoch. The observed LBG circular velocities are smaller than the predicted circular velocities by a factor >1.4+/-0.15. This is a lower limit as we have ignored any increase of circular velocity caused by baryonic dissipation. The massive-halo model predicts a median halo virial mass of 10^12.3 Msol, and a small spread of circular velocities. Our median estimated dynamical mass is <10^(11.6+/-0.3) Msol, which is significantly smaller; furthermore, the spread of our circular velocities is much larger than the massive-halo prediction. These results are consistent with a picture which leaves some of the most-massive haloes available for occupation by other populations which do not meet the LBG selection criteria. The median halo mass recently estimated by Adelberger et al. from the measured clustering of LBGs is 10^(11.86+/-0.3) Msol. Our dynamical analysis appears to favour lower masses and to be more in line with the median mass predicted by the collisional starburst model of Somerville et al., of 10^11.3 Msol. [abridged]Comment: 6 pages, 5 figures, MNRAS Letters, Accepte

HST Images of a Galaxy Group at z=2.81, and the Sizes of Damped Lyman Alpha Galaxies

We present HST WFPC2 observations in three bands (F450W, F467M and F814W) of a group of three galaxies at z=2.8 discovered in a ground-based narrow-band search for Lyman alpha emission near the z=2.8 quasar PKS0528-250. One of the galaxies is a damped (DLA) absorber and these observations bear on the relation between the DLA clouds and the Lyman-break galaxies and the stage in the evolution of galaxies they represent. We describe a procedure for combining the undersampled WFPC2 images pointed on a sub-pixel grid, which largely recovers the full sampling of the WFPC2 point spread function (psf). These three galaxies have similar properties to the Lyman-break galaxies except that they have strong Lyman alpha emission. The three galaxies are detected in all three bands, with average B~26, I~25. Two of the galaxies are compact with intrinsic (i.e. after correcting for the effect of the psf) half-light radii of ~0.1 arcsec (~0.4/h kpc, q_o=0.5). The third galaxy comprises two similarly compact components separated by 0.3 arcsec. The HST images and a new ground-based Lyman alpha image of the field provide evidence that the three galaxies are more extended in the light of Lyman alpha than in the continuum. The measured impact parameters for this DLA galaxy (1.17 arcsec), for a second confirmed system, and for several candidates, provide a preliminary estimate of the cross-section-weighted mean radius of the DLA gas clouds at z~3 of less than 13/h kpc, for q_o=0.5. Given the observed sky covering factor of the absorbers this implies that for q_o=0.5 the space density of DLA clouds at these redshifts is more than five times the space density of spiral galaxies locally, with the actual ratio probably considerably greater. For q_o=0.0 there is no evidence as yet that DLA clouds are more common than spiral galaxies locally.Comment: 11 pages, LaTeX, 6 Figures total (4 colour GIF-format, 2 PostScript), accepted for publication in MNRA

The Olympic transport legacy

This article examine sustainable transport provision for the London 2012Olympics and its intended legacy role in economic and social regeneration across East London. It concludes that ultimately, legacy success will depend on the ability to adapt to, and adopt, the new processes and cultural shifts over time, quickly assimilating them in a move towards more sustainable transport systems. The Olympics can put into place the foundations for a more sustainable society, but it needs more than this alone to realise the potential

Analysing road pricing implementation processes in the UK and Norway

Traditional transport policies of road expansion entail a relatively simple system of actors and processes around which expertise, knowledge, and skills which has built up over many decades. Some of the more radical Travel Demand Management measures, including urban road pricing, involve a complicated set of institutions, processes, people and procedures. Road pricing schemes often get delayed or abandoned due to controversy, disagreements, unanticipated problems and a whole host of other delaying factors. If they are implemented, they tend to be diluted and consequently become less effective. Strategic Niche Management (SNM) has previously been used to provide guidelines on the implementation of innovative transport technologies through setting up protected experimental settings (niches) in which actors learn about the design, user needs, social and political acceptability, and other aspects. Here SNM is modified to cover a policy approach through the analysis of road user charging case studies in the UK and Norway. A detailed analysis of the road user charging schemes in Bergen, Oslo, Durham and London is presented. Key factors identified include the role of stakeholder and user networks, the existence of a project champion, understanding the motivations and expectations of stakeholders and users, learning with regards to the regional context, and the change in perceptions associated with acceptance. Comparison between the four cases shows different approaches emerging from each country in implementing and ‘marketing’ of the policies. The paper concentrates on approaches such as: the purpose for introducing the policies, the involvement of users in the planning process and, the use of revenues for either providing alternative transport modes or financing road infrastructure. Key factors identified using the SNM framework include the role of stakeholder and user networks, the existence of a project champion, understanding the motivations and expectations of stakeholders and users, learning with regards to the regional context, and the change in perceptions associated with acceptance. This type of analysis could prove useful for transport planners envisaging the implementation of road pricing projects

Supporting policy packages: the future of road pricing in the UK

Transport is already a large component of our economy and society. Historically, transport programmes were substantially about developing basic infrastructure networks. Now the emphasis is on the active management of systems and operating them to maximum advantage in the face of growing travel demand and capacity limitations. Combined developments in technology and the world economy have accelerated change to almost unpredictable levels. The change affects many areas and transport is not an exception. With new vehicle technologies, radical policies and the persistent growth in private and commercial vehicles, a new changing transport landscape is emerging. One of these changes comes in the form of sustainable transport management - managing the demand of existing infrastructure networks. The role of demand management has been illustrated in many reports and papers and it seems that governments are becoming more aware of it. This paper focuses on one particular demand management policy that is often regarded as radical and generally unacceptable. Road pricing often gets delayed or abandoned due to controversy, disagreements, unanticipated problems and a whole host of other delaying factors. There are complex interactions in transport management - there is a need for cooperation between networks, stakeholders and different authorities. Single measures that focus on 'sustainable transport' usually address a limited set of objectives and are not usually combined with other policy measures. When combined, it is sometimes unclear whether the multiple interactions between policy tools and implementation networks have been considered. An emerging case of implementation of a policy package in the UK is the support of road pricing initiatives combined with public transport improvements by the Transport Innovation Fund. The paper will present a review of the UK road pricing situation along with key implementation factors that show firstly the importance of combining policy tools and secondly the necessity in creating and maintaining strong implementation networks

How to find MACHOs in the Virgo Cluster

We discuss the feasibility of finding extra-galactic MACHOs by monitoring quasars behind the Virgo cluster of galaxies. We show that with only a modest observing programme one could detect several MACHOs in the mass range 1 X 10^{-5} to 2 X 10^{-2} solar masses if they make a significant contribution to the mass of Virgo. The contamination by events from cosmologically distributed MACHOs is estimated and is negligible if either the MACHO mass is greater than about 10^{-4} solar masses or the quasar radius is greater than about 3 X 10^{15} cm.Comment: 5 pages, 1 figure, to appear in New Astronom