21,104 research outputs found
LoCuSS: Hydrostatic Mass Measurements of the High- Cluster Sample -- Cross-calibration of Chandra and XMM-Newton
We present a consistent analysis of Chandra and XMM-Newton observations of an
approximately mass-selected sample of 50 galaxy clusters at -- the
"LoCuSS High- Sample". We apply the same analysis methods to data from
both satellites, including newly developed analytic background models that
predict the spatial variation of the Chandra and XMM-Newton backgrounds to
and precision respectively. To verify the cross-calibration of
Chandra and XMM-Newton-based cluster mass measurements, we derive the mass
profiles of the 21 clusters that have been observed with both satellites,
extracting surface brightness and temperature profiles from identical regions
of the respective datasets. We obtain consistent results for the gas and total
hydrostatic cluster masses: the average ratio of Chandra- to XMM-Newton-based
measurements of and at are and
, respectively with an intrinsic scatter of for gas
masses and for hydrostatic masses. Comparison of our hydrostatic mass
measurements at with the latest LoCuSS weak-lensing results indicate
that the data are consistent with non-thermal pressure support at this radius
of . We also investigate the scaling relation between our hydrostatic
cluster masses and published integrated Compton parameter
measurements from the Sunyaev-Zel'dovich Array. We measure a scatter in mass at
fixed of at , which is consistent with
theoretical predictions of scatter.Comment: 21 pages, 11 figure
Three-Dimensional Time-Resolved Trajectories from Laboratory Insect Swarms
Aggregations of animals display complex and dynamic behaviour, both at the individual level and on the level of the group as a whole. Often, this behaviour is collective, so that the group exhibits properties that are distinct from those of the individuals. In insect swarms, the motion of individuals is typically convoluted, and swarms display neither net polarization nor correlation. The swarms themselves, however, remain nearly stationary and maintain their cohesion even in noisy natural environments. This behaviour stands in contrast with other forms of collective animal behaviour, such as flocking, schooling, or herding, where the motion of individuals is more coordinated, and thus swarms provide a powerful way to study the underpinnings of collective behaviour as distinct from global order. Here, we provide a data set of three-dimensional, time-resolved trajectories, including positions, velocities, and accelerations, of individual insects in laboratory insect swarms. The data can be used to study the collective as a whole as well as the dynamics and behaviour of individuals within the swarm
Unobtrusive and pervasive video-based eye-gaze tracking
Eye-gaze tracking has long been considered a desktop technology that finds its use inside the traditional office setting, where the operating conditions may be controlled. Nonetheless, recent advancements in mobile technology and a growing interest in capturing natural human behaviour have motivated an emerging interest in tracking eye movements within unconstrained real-life conditions, referred to as pervasive eye-gaze tracking. This critical review focuses on emerging passive and unobtrusive video-based eye-gaze tracking methods in recent literature, with the aim to identify different research avenues that are being followed in response to the challenges of pervasive eye-gaze tracking. Different eye-gaze tracking approaches are discussed in order to bring out their strengths and weaknesses, and to identify any limitations, within the context of pervasive eye-gaze tracking, that have yet to be considered by the computer vision community.peer-reviewe
CED: Color Event Camera Dataset
Event cameras are novel, bio-inspired visual sensors, whose pixels output
asynchronous and independent timestamped spikes at local intensity changes,
called 'events'. Event cameras offer advantages over conventional frame-based
cameras in terms of latency, high dynamic range (HDR) and temporal resolution.
Until recently, event cameras have been limited to outputting events in the
intensity channel, however, recent advances have resulted in the development of
color event cameras, such as the Color-DAVIS346. In this work, we present and
release the first Color Event Camera Dataset (CED), containing 50 minutes of
footage with both color frames and events. CED features a wide variety of
indoor and outdoor scenes, which we hope will help drive forward event-based
vision research. We also present an extension of the event camera simulator
ESIM that enables simulation of color events. Finally, we present an evaluation
of three state-of-the-art image reconstruction methods that can be used to
convert the Color-DAVIS346 into a continuous-time, HDR, color video camera to
visualise the event stream, and for use in downstream vision applications.Comment: Conference on Computer Vision and Pattern Recognition Workshop
On-sky speckle nulling demonstration at small angular separation with SCExAO
This paper presents the first on-sky demonstration of speckle nulling, which
was achieved at the Subaru Telescope in the context of the Subaru Coronagraphic
Extreme Adaptive Optics (SCExAO) Project. Despite the absence of a high-order
high-bandwidth closed-loop AO system, observations conducted with SCExAO show
that even in poor-to-moderate observing conditions, speckle nulling can be used
to suppress static and slow speckles even in the presence of a brighter dynamic
speckle halo, suggesting that more advanced high-contrast imaging algorithms
developed in the laboratory can be applied to ground-based systems.Comment: 5 figures, accepted for publication by PAS
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