Constraining the Mass Profiles of Stellar Systems: Schwarzschild Modeling of Discrete Velocity Datasets

(ABRIDGED) We present a new Schwarzschild orbit-superposition code designed to model discrete datasets composed of velocities of individual kinematic tracers in a dynamical system. This constitutes an extension of previous implementations that can only address continuous data in the form of (the moments of) velocity distributions, thus avoiding potentially important losses of information due to data binning. Furthermore, the code can handle any combination of available velocity components, i.e., only line-of-sight velocities, only proper motions, or a combination of both. It can also handle a combination of discrete and continuous data. The code finds the distribution function (DF, a function of the three integrals of motion E, Lz, and I3) that best reproduces the available kinematic and photometric observations in a given axisymmetric gravitational potential. The fully numerical approach ensures considerable freedom on the form of the DF f(E,Lz,I3). This allows a very general modeling of the orbital structure, thus avoiding restrictive assumptions about the degree of (an)isotropy of the orbits. We describe the implementation of the discrete code and present a series of tests of its performance based on the modeling of simulated datasets generated from a known DF. We find that the discrete Schwarzschild code recovers the original orbital structure, M/L ratios, and inclination of the input datasets to satisfactory accuracy, as quantified by various statistics. The code will be valuable, e.g., for modeling stellar motions in Galactic globular clusters, and those of individual stars, planetary nebulae, or globular clusters in nearby galaxies. This can shed new light on the total mass distributions of these systems, with central black holes and dark matter halos being of particular interest.Comment: ApJ, in press; 51 pages, 11 figures; manuscript revised following comments by refere

Building up the Stellar Halo of the Galaxy

We study numerical simulations of satellite galaxy disruption in a potential resembling that of the Milky Way. Our goal is to assess whether a merger origin for the stellar halo would leave observable fossil structure in the phase-space distribution of nearby stars. We show how mixing of disrupted satellites can be quantified using a coarse-grained entropy. Although after 10 Gyr few obvious asymmetries remain in the distribution of particles in configuration space, strong correlations are still present in velocity space. We give a simple analytic description of these effects, based on a linearised treatment in action-angle variables, which shows how the kinematic and density structure of the debris stream changes with time. By applying this description we find that a single satellite of current luminosity 10^8 L_\sun disrupted 10 Gyr ago from an orbit circulating in the inner halo (mean apocentre $\sim 12$ kpc) would contribute about $\sim 30$ kinematically cold streams with internal velocity dispersions below 5 km/s to the local stellar halo. If the whole stellar halo were built by disrupted satellites, it should consist locally of 300 - 500 such streams. Clear detection of all these structures would require a sample of a few thousand stars with 3-D velocities accurate to better than 5 km/s. Even with velocity errors several times worse than this, the expected clumpiness should be quite evident. We apply our formalism to a group of stars detected near the North Galactic Pole, and derive an order of magnitude estimate for the initial properties of the progenitor system.Comment: 28 pages, 10 figures, minor changes, matches the version to appear in MNRAS, Vol. 307, p.495-517 (August 1999

Playwork goes to School:Professional (mis)recognition and playwork practice in primary school.

The article considers some of the key contemporary challenges facing playwork professionals in England when working in interagency and inter-professional contexts, specifically in English primary schools. This paper is based on a small-scale qualitative evaluation of a pilot play project situated within a primary school in a large English town. By drawing on broader debates within sociological literature and interview and observational data, this paper provides insights into the gendered, classed and interprofessional discourses that are in play within a new phase of the austere economic and occupational public sector landscape. Drawing on concepts of ‘misrecognition’, the authors’ explore issues of professional power, the process of professionalisation and how aspects such as gender and status shape contemporary inter-professional dynamics in schools and playwork contexts

Elliptical Galaxy Dynamics

A review of elliptical galaxy dynamics, with a focus on nonintegrable models. Topics covered include torus construction; modelling axisymmetric galaxies; triaxiality; collisionless relaxation; and collective instabilities.Comment: 97 Latex pages, 14 Postscript figures, uses aastex. To appear in Publications of the Astronomical Society of the Pacific, February 199

A hierarchical model of children’s research participation rights based on information, understanding, voice, and influence

© 2018, © 2018 EECERA. This paper introduces a hierarchical model of children’s (3- to 8-year olds) research participation rights that builds on work by Roger Hart and integrates key participation rights drawn from UNCRC Article 12: information, understanding, voice, and influence. It provides insight into the various levels of information that can be provided to children, the understanding that results, the scope given to them to express their views, and the degree to which their voices ultimately exert influence in research contexts. Each of these four elements plays a unique role in upholding and enhancing children’s rights in research and emphasises the need for rights to be woven into the fabric of a research project from its conception. Considering children’s rights of research participation in a more integrated manner, as suggested by the hierarchy, has the potential to improve participation experiences for children and to value them as citizens with meaningful rights

Future Socio-political Scenarios for Aquatic Resources in Europe : An Operationalized Framework for Marine Fisheries Projections

Climate change is anticipated to have long-term and widespread direct consequences for the European marine ecosystems and subsequently for the European fishery sector. Additionally, many socio-economic and political factors linked to climate change scenarios will impact the future development of fishing industries. Robust projection modeling of bioeconomic consequences of climate change on the European fishing sector must identify all these factors and their potential future interaction. In this study, four socio-political scenarios developed in the EU project CERES (Climate change and European aquatic RESources) were operationalized and used in model projections of marine wild capture fisheries. Four CERES scenarios (“World Markets,” “National Enterprise,” “Global Sustainability” and “Local Stewardship”) were based on the IPCC framework of Shared Socio-economic Pathways (SSPs). For each of these scenarios, a set of quantitative outputs was generated to allow projections of bio-economic impacts to mid-century (2050) on wild-capture fisheries operating in different European regions. Specifically, projections accounted for future changes in fisheries management targets, access regulations, international agreements, fish and fuel prices, technological developments and marine spatial planning. This study thoroughly describes the elements of these four fisheries scenarios and demonstrates an example of the “regionalization” of these scenarios by summarizing how they were applied to the North Sea flatfish fishery. Bioeconomic projections highlight the importance of future developments in fuel and fish price development to the viability of that and other fisheries. Adapting these scenarios for use in other models and regions outside the 10 European fisheries examined in CERES would be highly beneficial by allowing direct comparison of the bioeconomic risks and opportunities posed by climate change.</p

Service responses to South Asian women who attempt suicide or self-harm: challenges for service commissioning and delivery

This article draws on an investigation of service responses to women of South Asian background who have attempted suicide or self-harm within northwest England to outline policy challenges for adequate provision to this population. This article highlights, in particular, the challenges for service managers arising from and documented within the study, outlining implications for improving policy, service commissioning and provision. We suggest that these omissions have resulted in the distress of South Asian women going unrecognized in the name of respect for cultural diversity, thereby sanctioning policies and practices that further the oppression of South Asian women. Four main issues emerging from the interviews are discussed: 1) the impact of the contract culture on the form and structure of service provision; 2) limitations of current partnership arrangements with South Asian communities; 3) practical and conceptual problems within models of both consultation and change; and, 4) key practical consequences of the covert ways in which the structure and interpretation of service responses work to treat `race' as more important than gender. In terms of specific implications, it is suggested that the current policy focus on addressing service inequalities via recruitment of South Asian workers warrants critical re-evaluation, while training and management development should take as central the intersections of `race', culture, class and gender as systemic issues to be worked with rather than marginal or optional considerations. It is argued that attending to the specific needs and conditions of South Asian women attempting suicide or self-harm by providing integrated culturally and gender-sensitive services highlights good practice for everyone