716 research outputs found
The Evolution of X-Ray Clusters in a Cold Plus Hot Dark Matter Universe
We present the first self-consistently computed results on the evolution of
X-ray properties of galaxy clusters in a Cold + Hot Dark Matter (CHDM) model.
We have performed a hydrodynamic plus N-body simulation for the COBE-compatible
CHDM model with standard mass components: Omega(hot) = 0.3, Omega(cold) = 0.6
and Omega(baryon) = 0.1 (h = 0.5). In contrast with the CDM model, which fails
to reproduce the observed temperature distribution function dN/dT (Bryan et al.
1994b), the CHDM model fits the observational dN/dT quite well. Our results on
X-ray luminosity are less firm but even more intriguing. We find that the
resulting X-ray luminosity functions at redshifts z = 0.0, 0.2, 0.4, 0.7 are
well fit by observations, where they overlap. The fact that both temperatures
and luminosities provide a reasonable fit to the available observational data
indicates that, unless we are missing some essential physics, there is neither
room nor need for a large fraction of gas in rich clusters: 10% (or less) in
baryons is sufficient to explain their X-ray properties. We also see a tight
correlation between X-ray luminosity and gas temperature.Comment: 11 pages, 3 figures uuencoded postscript file, (92 kb), accepted for
publication in Astrophysical Journal Letters. Also available via anonymous
ftp at zeus.ncsa.uiuc.edu in gc3/publications/gc3005, LCA01
A Universal Temperature Profile for Galaxy Clusters
We investigate the predicted present-day temperature profiles of the hot,
X-ray emitting gas in galaxy clusters for two cosmological models - a current
best-guess LCDM model and standard cold dark matter (SCDM). Our
numerically-simulated "catalogs" of clusters are derived from high-resolution
(15/h kpc) simulations which make use of a sophisticated, Eulerian-based,
Adaptive Mesh-Refinement (AMR) code that faithfully captures the shocks which
are essential for correctly modelling cluster temperatures. We show that the
temperature structure on Mpc-scales is highly complex and non-isothermal.
However, the temperature profiles of the simulated LCDM and SCDM clusters are
remarkably similar and drop-off as
where and . This decrease
is in good agreement with the observational results of Markevitch et al.(1998)
but diverges, primarily in the innermost regions, from their fit which assumes
a polytropic equation of state. Our result is also in good agreement with a
recent sample of clusters observed by BeppoSAX though there is some indication
of missing physics at small radii (). We discuss the
interpretation of our results and make predictions for new x-ray observations
that will extend to larger radii than previously possible. Finally, we show
that, for , our universal temperature profile is consistent with
our most recent simulations which include both radiative cooling and supernovae
feedback.Comment: 8 pages, 6 figures, accepted for publication in ApJ, full-page
version of Fig. 2 at
http://www.cita.utoronto.ca/+AH4-cloken/PAPERS/UTP/f2.ep
Does an athlete's anger differ by sport type and gender?
Anger is an emotion that is frequently associated with a bad reputation. Anger has proven to play an effective role in certain athletic achievements; however, it is unknown which sport and gender have the athletes whose performance is most influenced by anger. In this study, we administered the STAXI-2 to determine relationships between gender and levels of athlete anger in 156 British athletes across a range of contact and non-contact sports and competitive levels (from professional/Olympians to recreational). We investigated differences in levels of anger in relation to the sport they played. Although not statistically significant, the results indicated that male athletes scored higher in trait, expression-out, anger control-out, and overall anger index, but females scored higher in state anger. The findings revealed that athletes in contact sports have higher levels of trait anger, but non contact athletes have higher levels of state anger. This study’s findings imply that anger does not influence all athletes similarly because anger is subjective to persons and sports
Language-Guided Audio-Visual Source Separation via Trimodal Consistency
We propose a self-supervised approach for learning to perform audio source
separation in videos based on natural language queries, using only unlabeled
video and audio pairs as training data. A key challenge in this task is
learning to associate the linguistic description of a sound-emitting object to
its visual features and the corresponding components of the audio waveform, all
without access to annotations during training. To overcome this challenge, we
adapt off-the-shelf vision-language foundation models to provide pseudo-target
supervision via two novel loss functions and encourage a stronger alignment
between the audio, visual and natural language modalities. During inference,
our approach can separate sounds given text, video and audio input, or given
text and audio input alone. We demonstrate the effectiveness of our
self-supervised approach on three audio-visual separation datasets, including
MUSIC, SOLOS and AudioSet, where we outperform state-of-the-art strongly
supervised approaches despite not using object detectors or text labels during
training.Comment: Accepted at CVPR 202
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