6,250 research outputs found
The Seven Sisters DANCe III: Projected spatial distribution
Methods. We compute Bayesian evidences and Bayes Factors for a set of
variations of the classical radial models by King (1962), Elson et al. (1987)
and Lauer et al. (1995). The variations incorporate different degrees of model
freedom and complexity, amongst which we include biaxial (elliptical) symmetry,
and luminosity segregation. As a by-product of the model comparison, we obtain
posterior distributions and maximum a posteriori estimates for each set of
model parameters. Results. We find that the model comparison results depend on
the spatial extent of the region used for the analysis. For a circle of 11.5
parsecs around the cluster centre (the most homogeneous and complete region),
we find no compelling reason to abandon Kings model, although the Generalised
King model, introduced in this work, has slightly better fitting properties.
Furthermore, we find strong evidence against radially symmetric models when
compared to the elliptic extensions. Finally, we find that including mass
segregation in the form of luminosity segregation in the J band, is strongly
supported in all our models. Conclusions. We have put the question of the
projected spatial distribution of the Pleiades cluster on a solid probabilistic
framework, and inferred its properties using the most exhaustive and least
contaminated list of Pleiades candidate members available to date. Our results
suggest however that this sample may still lack about 20% of the expected
number of cluster members. Therefore, this study should be revised when the
completeness and homogeneity of the data can be extended beyond the 11.5
parsecs limit. Such study will allow a more precise determination of the
Pleiades spatial distribution, its tidal radius, ellipticity, number of objects
and total mass.Comment: 39 pages, 31 figure
Las matemáticas en el bachillerato a distancia: restricciones epistemológicas y pedagógicas
El mundo está experimentando una verdadera revolución en la difusión del conocimiento y en la mejora de la instrucción a través del avance de las tecnologías de la comunicación y la información. Esta es la tercera revolución en el aprendizaje, siendo la primera la invención del lenguaje escrito y la segunda el desarrollo de la imprenta y los libros. En la actualidad podemos encontrar enseñanza virtual en todos los niveles de enseñanza, es por ello que los sistemas educativos se enfrentan a grandes desafíos en la cada vez más demanda educación a distancia, con el propósito de proporcionar todo el espectro de servicios de educación para todos, en cualquier lugar y en cualquier momento con un enfoque centrado en un aprendizaje efectivo. A pesar de este gran desarrollo de la educación a distancia, no existen muchos estudios al respecto. La finalidad de este trabajo es estudiar las restricciones de orden epistemológico y pedagógico que puede presentar la enseñanza de las matemáticas en el bachillerato a distancia
Cloning of Gaussian states by linear optics
We analyze in details a scheme for cloning of Gaussian states based on linear
optical components and homodyne detection recently demonstrated by U. L.
Andersen et al. [PRL 94 240503 (2005)]. The input-output fidelity is evaluated
for a generic (pure or mixed) Gaussian state taking into account the effect of
non-unit quantum efficiency and unbalanced mode-mixing. In addition, since in
most quantum information protocols the covariance matrix of the set of input
states is not perfectly known, we evaluate the average cloning fidelity for
classes of Gaussian states with the degree of squeezing and the number of
thermal photons being only partially known.Comment: 8 pages, 7 figure
The Seven Sisters DANCe. I. Empirical isochrones, Luminosity and Mass Functions of the Pleiades cluster
The DANCe survey provides photometric and astrometric (position and proper
motion) measurements for approximately 2 millions unique sources in a region
encompassing 80deg centered around the Pleiades cluster.
We aim at deriving a complete census of the Pleiades, and measure the mass
and luminosity function of the cluster. Using the probabilistic selection
method described in Sarro+2014, we identify high probability members in the
DANCe (14mag) and Tycho-2 (12mag) catalogues, and study the
properties of the cluster over the corresponding luminosity range. We find a
total of 2109 high probability members, of which 812 are new, making it the
most extensive and complete census of the cluster to date. The luminosity and
mass functions of the cluster are computed from the most massive members down
to 0.025M. The size, sensitivity and quality of the sample
result in the most precise luminosity and mass functions observed to date for a
cluster. Our census supersedes previous studies of the Pleiades cluster
populations, both in terms of sensitivity and accuracy.Comment: Language Edition Done. Final version to be published in A&A. Tables
will be published at CDS. Meanwhile, they can be requested to H. Bouy (hbouy
-at- cab . inta - csic . es
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