Physical component analysis of galaxy cluster weak gravitational lensing data

We present a novel approach for reconstructing the projected mass distribution of clusters of galaxies from sparse and noisy weak gravitational lensing shear data. The reconstructions are regularised using knowledge gained from numerical simulations of clusters: trial mass distributions are constructed from N physically-motivated components, each of which has the universal density profile and characteristic geometry observed in simulated clusters. The parameters of these components are assumed to be distributed \emph{a priori} in the same way as they are in the simulated clusters. Sampling mass distributions from the components' parameters' posterior probability density function allows estimates of the mass distribution to be generated, with error bars. The appropriate number of components is inferred from the data itself via the Bayesian evidence, and is typically found to be small, reflecting the quality of the simulated data used in this work. Ensemble average mass maps are found to be robust to the details of the noise realisation, and succeed in recovering the input mass distribution (from a realistic simulated cluster) over a wide range of scales. We comment on the residuals of the reconstruction and their implications, and discuss the extension of the method to include strong lensing information.Comment: 12 pages, 7 figure

Health and well-being implications surrounding the use of wearable GPS devices in professional rugby league: A Foucauldian disciplinary analysis of the normalised use of a common surveillance aid

Wearable GPS tracking devices have become commonplace coaching aids across professional field sports to enhance sports performances and reduce injury rates, despite the implications of the technology being poorly understood. This study looked at how GPS devices are used and the impact constant surveillance has upon the physical, psychological, and emotional health of rugby football workers. The disciplinary analysis of Michel Foucault was used to investigate how British Super League teams use wearable GPS technology, to investigate the dominant 'truth' that promotes surveillance technologies as 'universally beneficial' to athlete sports performance, health and well-being. Data was drawn from semi-structured interviews with three performance analysts/strength and conditioning coaches at three different Super League clubs across the North of England. Participants confessed data generated from wearable GPS is often totally ignored, despite being specifically produced to protect athlete health and wellbeing. When used, GPS data can become a 'disciplinary tool' to normalise and coerce players to comply with potentially unhealthy physical and psychological demands of a professional playing career. Importantly, regardless of how GPS data was used, the employment of wearable GPS devices was constantly and rigorously implemented. The constant surveillance experience by working players, when mismanaged or adopted as a coercive disciplinary tool, magnifies the uncertainty and fear of failure central to the predominant challenges that arise during a working football career. This leads to the acceptance of problematic norms damaging to physical, psychological, and emotional health. If GPS or other surveillance based performance analysis technologies are to be used in sport, coaches need to regulate or re-think their day-to-day use to avoid creating new harms to athlete health and well-being

The SNAP Strong Lens Survey

Basic considerations of lens detection and identification indicate that a wide field survey of the types planned for weak lensing and Type Ia SNe with SNAP are close to optimal for the optical detection of strong lenses. Such a ``piggy-back'' survey might be expected even pessimistically to provide a catalogue of a few thousand new strong lenses, with the numbers dominated by systems of faint blue galaxies lensed by foreground ellipticals. After sketching out our strategy for detecting and measuring these galaxy lenses using the SNAP images, we discuss some of the scientific applications of such a large sample of gravitational lenses: in particular we comment on the partition of information between lens structure, the source population properties and cosmology. Understanding this partitioning is key to assessing strong lens cosmography's value as a cosmological probe.Comment: 6 pages, 4 figures. To appear in the conference proceedings of "Wide Field Imaging from Space" (published in New Astronomy Reviews), eds. T. McKay, A. Fruchter, and E. Linde

Complex training: The effect of exercise selection and training status on postactivation potentiation in rugby league players

This study compared the postactivation potentiation (PAP) response of the hex bar deadlift (HBD) and back squat (BS) exercises. The PAP response between different levels of athletes was also compared. Ten professional and 10 amateur rugby league players performed 2 experimental sessions. Participants performed a countermovement jump (CMJ) before and 2, 4, 6, 8, 10, 12, 14, and 16 minutes after a conditioning activity (CA) that contained 1 set of 3 repetitions at 93% 1 repetition maximum of either HBD or BS. A force platform determined peak power output (PPO), force at PPO, velocity at PPO, and jump height of each CMJ. Surface electromyography (EMG) of the vastus lasteralis, rectus femoris, tibialis anterior, and gastrocnemius medialis of each participant's dominant leg was recorded during each CMJ. A further 10 participants performed a control trial without a CA. The HBD expressed PAP between 2 and 6 minutes post-CA, whereas the BS did not. The HBD exhibited a significantly (p ≤ 0.05) greater PAP response than the BS for PPO. There were no significant (p > 0.05) differences between stronger and weaker players. There were no significant (p > 0.05) changes in the EMG variables. These results suggest that HBD is a suitable CA for eliciting PAP in stronger and weaker athletes. Strength and conditioning coaches should consider the CA and time frame between the CA and the plyometric exercise for optimal PAP responses

Combining internal- and external-training-load measures in professional rugby league

Purpose: This study investigated the effect of training mode on the relationships between measures of training load in professional rugby league players. Methods: Five measures of training load (internal: individualized training impulse, session rating of perceived exertion; external—body load, high-speed distance, total impacts) were collected from 17 professional male rugby league players over the course of two 12-week pre-season periods. Training was categorized by mode (small-sided games, conditioning, skills, speed, strongman, and wrestle) and subsequently subjected to a principal component analysis. Extraction criteria were set at an eigenvalue of greater than one. Modes that extracted more than one principal component were subjected to a varimax rotation. Results: Small-sided games and conditioning extracted one principal component, explaining 68% and 52% of the variance, respectively. Skills, wrestle, strongman, and speed extracted two principal components explaining 68%, 71%, 72%, and 67% of the variance respectively. Conclusions: In certain training modes the inclusion of both internal and external training load measures explained a greater proportion of the variance than any one individual measure. This would suggest that in those training modes where two principal components were identified, the use of only a single internal or external training load measure could potentially lead to an underestimation of the training dose. Consequently, a combination of internal and external load measures is required during certain training modes

AMUSE-Virgo I. Super-massive black holes in low-mass spheroids

We present the first results from the AGN Multiwavelength Survey of Early-type galaxies in the Virgo cluster (AMUSE-Virgo). This large program targets 100 early-type galaxies with the Advanced CCD Imaging Spectrometer on board the Chandra X-ray Observatory and the Multi-band Imaging Photometer on board the Spitzer Space Telescope, with the aim of providing an unbiased census of low-level super-massive black hole (SMBH) activity in the local universe. Here we report on the Chandra observations of the first 16 targets, and combine them with results from archival data of another, typically more massive, 16 targets. Point-like X-ray emission from a position coincident with the optical nucleus is detected in 50% of the galaxies (down to our completeness limit of ~4E+38 erg/sec). Two of the X-ray nuclei are hosted by galaxies (VCC1178=N4464 and VCC1297=N4486B) with absolute B magnitudes fainter than -18, where nuclear star clusters are known to become increasingly common. After carefully accounting for possible contamination from low mass X-ray binaries, we argue that the detected nuclear X-ray sources are most likely powered by low-level accretion on to a SMBH, with a <11% chance contamination in VCC1178, where a star cluster is barely resolvable in archival Hubble Space Telescope images. Based on black hole mass estimates from the global properties of the host galaxies, all the detected nuclei are highly sub-Eddington, with luminosities in the range -8.4<log(L_0.3-10keV/L_Edd)<-5.9. The incidence of nuclear X-ray activity increases with the stellar mass M_star of the host galaxy: only between 3-44% of the galaxies with M_star<1E+10 M_Sun harbor an X-ray active SMBH. The fraction rises to between 49-87% in galaxies with stellar mass above 1E+10 M_Sun (at the 95% confidence level).Comment: Revised version, accepted by Ap

An Atlas of Predicted Exotic Gravitational Lenses

Wide-field optical imaging surveys will contain tens of thousands of new strong gravitational lenses. Some of these will have new and unusual image configurations, and so will enable new applications: for example, systems with high image multiplicity will allow more detailed study of galaxy and group mass distributions, while high magnification is needed to super-resolve the faintest objects in the high redshift universe. Inspired by a set of six unusual lens systems [including five selected from the Sloan Lens ACS (SLACS) and Strong Lensing Legacy (SL2S) surveys, plus the cluster Abell 1703], we consider several types of multi-component, physically-motivated lens potentials, and use the ray-tracing code "glamroc" to predict exotic image configurations. We also investigate the effects of galaxy source profile and size, and use realistic sources to predict observable magnifications and estimate very approximate relative cross-sections. We find that lens galaxies with misaligned disks and bulges produce swallowtail and butterfly catastrophes, observable as "broken" Einstein rings. Binary or merging galaxies show elliptic umbilic catastrophes, leading to an unusual Y-shaped configuration of 4 merging images. While not the maximum magnification configuration possible, it offers the possibility of mapping the local small-scale mass distribution. We estimate the approximate abundance of each of these exotic galaxy-scale lenses to be ~1 per all-sky survey. In higher mass systems, a wide range of caustic structures are expected, as already seen in many cluster lens systems. We interpret the central ring and its counter-image in Abell 1703 as a "hyperbolic umbilic" configuration, with total magnification ~100 (depending on source size). The abundance of such configurations is also estimated to be ~1 per all-sky survey.Comment: 21 pages, 30 figures, accepted by MNRAS, copyright material cleared for re-printing. High-resolution version available from http://www.slac.stanford.edu/~pjm/atla

Drawing: an ambiguous practice

Is a lack of a definition, a position of ambiguity, desirable in response to the question: what is drawing? This paper presents a view taken from two traditionally distinct fields: art and design; design and technology. This view is formed through the research collaboration and co-editorship of TRACEY: the journal of contemporary drawing, and the pedagogical development of a Masters programme in visualisation by the authors. This view is that a lack of definition is not only desirable, it is also a necessity. Our position is that the ambiguity that inevitably stems from a lack of definition forms a strategy that enables and sustains drawing research. Our collaborative experience is that drawing research is framed by assumptions that are embedded within art and design; design and technology. Historically, these fields have developed particular views about what drawing is, or what drawing is not. This paper will attempt to break down these assumptions from the place and space that evolves through the authors’ ongoing experience of collaboration. From this place and space we will argue that there are a number of art / design categories of practice and research that ultimately describe something that is bounded (area / volume). These overlap, intersect, and perhaps like some long standing boundary war, vie for ownership of each other’s domains. Drawing could be seen as one of these domains. However, we will argue that drawing is unbounded, that there is no ‘expanded field’, and that drawing’s ubiquity necessitates a lack of definition, a position of ambiguity. A boundary can change over time for many reasons: a diverted water course, or a wooden fence that moves slightly every time it is replaced. The reason for such changes is rarely recorded and can lead to disputes (RICS, 2009)

Toward [hyper] drawing… through ambiguity

This article explores ambiguity in contemporary fine art drawing through the presentation of a proposal and subsequent response. Drawing within three figurations: Empson’s seven types of ambiguity in literary prose (first published in 1930), the logical fallacies of ambiguity, and grammatical prepositions (e.g. between, beyond, beside etc.) the article aims to investigate the opportunities that arise if we are ambivalent to, subvert, or challenge definitions of drawing. The article critiques the origins of hyperdrawing tracing from a point of retrieval, where a conceptual and practical view ‘point’ is set into motion (Hill 1966: 44) beginning with a revisiting of the author’s previous research into this hyper view (Sawdon and Marshall, 2009). This trace moves through the three figurations: mapping the seven ambiguities, overlaid and interwoven with five fallacies, drawing emergent prepositions, in advancing logical disorder. An example drawn response, titled Seventh (from a series of drawings titled First through to Seventh), is selectively unwoven in the context of the figurations. The article discusses the opportunities highlighted through this response, returning to the proposal that a position of ambiguity (a lack of definition) is desirable and presents a fallacious definition. Ultimately (drawing) ambiguity is left unresolved, however its opportunities are explored through an examination of the boundary between literary criticism and drawin