10,268 research outputs found
An Elliptical Galaxy Luminosity Function and Velocity Dispersion Sample of Relevance for Gravitational Lensing Statistics
We have selected 42 elliptical galaxies from the literature and estimated
their velocity dispersions at the effective radius (\sigma_{\re}) and at 0.54
effective radii (\vff). We find by a dynamical analysis that the normalized
velocity dispersion of the dark halo of an elliptical galaxy \vdm is roughly
\sigma_{\re} multiplied by a constant, which is almost independent of the
core radius or the anisotropy parameter of each galaxy. Our sample analysis
suggests that \vdm^{*} lies in the range 178-198 km s. The power law
relation we find between the luminosity and the dark matter velocity dispersion
measured in this way is (L/L^{*}) = (\vdm/\vdm^{*})^\gamma, where is
between 2-3. These results are of interest for strong gravitational lensing
statistics studies.
In order to determine the value of \vdm^{*}, we calculate \mstar in the
same \bt band in which \vdm^{*} has been estimated. We select 131
elliptical galaxies as a complete sample set with apparent magnitudes \bt
between 9.26 and 12.19. We find that the luminosity function is well fitted to
the Schechter form, with parameters \mstar = -19.66 + 5, , and the normalization constant Mpc, with the Hubble constant
\hnot = 100 km s Mpc. This normalization implies that
morphology type E galaxies make up (10.8 1.2) per cent of all galaxies.Comment: 18 pages latex, with ps figs included. accepted by New Astronomy
(revised to incorporate referees comments
Collider Searches for Long-Lived Particles Beyond the Standard Model
Experimental tests of the Standard Model of particle physics (SM) find
excellent agreement with its predictions. Since the original formation of the
SM, experiments have provided little guidance regarding the explanations of
phenomena outside the SM, such as the baryon asymmetry and dark matter. Nor
have we understood the aesthetic and theoretical problems of the SM, despite
years of searching for physics beyond the Standard Model (BSM) at particle
colliders. Some BSM particles can be produced at colliders yet evade being
discovered, if the reconstruction and analysis procedures not matched to
characteristics of the particle. An example is particles with large lifetimes.
As interest in searches for such long-lived particles (LLPs) grows rapidly, a
review of the topic is presented in this article. The broad range of
theoretical motivations for LLPs and the experimental strategies and methods
employed to search for them are described. Results from decades of LLP searches
are reviewed, as are opportunities for the next generation of searches at both
existing and future experiments.Comment: 79 pages, 36 figures, submitted to Progress in Particle and Nuclear
Physic
Task-Driven Adaptive Statistical Compressive Sensing of Gaussian Mixture Models
A framework for adaptive and non-adaptive statistical compressive sensing is
developed, where a statistical model replaces the standard sparsity model of
classical compressive sensing. We propose within this framework optimal
task-specific sensing protocols specifically and jointly designed for
classification and reconstruction. A two-step adaptive sensing paradigm is
developed, where online sensing is applied to detect the signal class in the
first step, followed by a reconstruction step adapted to the detected class and
the observed samples. The approach is based on information theory, here
tailored for Gaussian mixture models (GMMs), where an information-theoretic
objective relationship between the sensed signals and a representation of the
specific task of interest is maximized. Experimental results using synthetic
signals, Landsat satellite attributes, and natural images of different sizes
and with different noise levels show the improvements achieved using the
proposed framework when compared to more standard sensing protocols. The
underlying formulation can be applied beyond GMMs, at the price of higher
mathematical and computational complexity
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