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

Learning on the move: exploring work with vulnerable young men through the lens of movement

This paper discusses a practice context in which process and movement are central to the provision of care and support. It draws on data from a research project conducted with The Men’s Room, Manchester, England which used ethnographic and mobile methods to explore the complex task staff undertake in engaging and supporting highly vulnerable young men. The organisation’s commitment to getting alongside these young men includes a mobile and highly improvised use of temporary city centre spaces for delivering its work. In this paper, I argue that these movements of practice are not simply a logistical necessity or a physical activity, but involve a kinetic way of attending, reflecting, thinking and knowing in which the organisation’s movements are intrinsic to the provision of care and support

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

Claiming Space and Struggling for Recognition Partispace Working Paper Two

Aiming at contributing to a better understanding of the current developments, paradoxes and ways to deal with youth political participation in Europe, the main research question of the PARTISPACE project is: How and where do 15- to 30 year-old young people participate differently across social milieus and youth cultural scenes and across eight European cities (framed by different national welfare, education and youth policies)? In relation to this research question, this report was intended to analyse case studies which explore participation practices in formal, non-formal and informal contexts and reconstruct practices, meanings, relationship and dynamics of different forms of youth participation in a comparative perspective and local constellations of youth participation. In so doing, the report has outlined a mosaic of the different practices, activities, styles and spaces wherein young people situate their participation in the eight countries involved in the PARTISPACE project

Report of the JRC’s Descriptor 1 workshop to support the review of the Commission Decision 2010/477/EU concerning MSFD criteria for assessing Good Environmental Status

The MSFD workshop on biodiversity (MSFD D1), held in Ispra JRC (7th-9th of September 2015) aimed to provide clear proposals and conclusions on some of the outstanding issues identified in the D1 review manual (May 2015 consultation version: https://circabc.europa.eu/w/browse/46d2b7ba-d2fd-4b3c-9eaf-18c7cb702b53) in the broader context of support to the review of Commission Decision 2010/477/EU. This report is complementing the Commission Decision 2010/477/EU review manual (JRC96521) and presents the result of the scientific and technical review concluding phase 1 of the review of the Commission Decision 2010/477/EU in relation to Descriptor 1. The review has been carried out by the EC JRC together with experts nominated by EU Member States, and has considered contributions from the GES Working Group in accordance with the roadmap set out in the MSFD implementation strategy (agreed on at the 11th CIS MSCG meeting). The main issues addressed and tackled in this workshop’s report are: - Common lists of elements for the biodiversity assessments (species & habitats) o Review of the “Biological Features” in Table 1 in the MSFD Annex III in relation to D1 requirements o Review of the “Habitat Types” entries in Table 1 in the MSFD Annex III in relation to D1 requirements - Selection/deselection criteria for the inclusion of species and habitats in a group - Updated criteria and indicators for D1 - Habitat/Bird Directives, WFD, Common Fisheries Policy and D1 o Use of species and habitats for the MSFD needs that are already included in other legislation and agreements o Links between status classification approaches (FCS vs GES, GEcS vs GES) - Streamlining of assessments, including scales of assessments - Cross-cutting issues related to D1 implementation o Aggregation rules within D1 criteria/indicators o Final GES integration across descriptors assessments Steps forward and technical needs for D1.JRC.H.1-Water Resource

Regimes of youth participation? Comparative analysis of youth policies and participation across European cities

This paper problematizes the assumption that national policies have a direct impact on youth participation at local level and analyses the relationships between local forms of youth participation and local and national policies. Relying on data from a EU project, the paper focuses on formally institutionalised settings of youth participation and elaborates local constellations of youth participation in six European cities. These constellations may be referred to as regimes of youth participation as they reflect wider structures of power and knowledge that influence the way in which young people’s practices in public spaces and their claims of being part of society are recognised. However, the analysis reveals that rather deducing it from the model of welfare regimes, such a typology needs to be developed starting from the local level and should consider the ways in which different relationships between local youth policies and national welfare states affect youth participation

Stable Models of Elliptical Galaxies

We construct stable axially symmetric models of elliptical galaxies. The particle density on phase space for these models depends monotonically on the particle energy and on the third component of the angular momentum. They are obtained as minimizers of suitably defined energy-Casimir functionals, and this implies their nonlinear stability. Since our analysis proceeds from a rigorous but purely mathematical point of view it should be interesting to determine if any of our models match observational data in astrophysics. The main purpose of these notes is to initiate some exchange of information between the astrophysics and the mathematics communities.Comment: 26 page

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

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

Gender, migration and exclusionary citizenship regimes: conceptualizing transnational abandonment of wives as a form of violence against women

Based on life-history narratives of 57 women in India who married Indian-origin men settled (primarily) in the West and interviews with 21 practitioners, we document the neglect, abuse and instrumental deprivation of the women’s rights in the process of transnational abandonment. Gendered local socio-cultural milieus and economic norms contribute to these harms in a context where women’s identity and social status are closely connected to marriage. However, these harms are enabled and sustained by transnational formal-legal frameworks which make women subordinate citizens. Widening the explanatory lens for understanding domestic violence beyond the family and community, we argue that in a globalised world, (inter)state policies serve to construct categories of ‘disposable women’ who can be abused and abandoned with impunity