1,439 research outputs found
The ALHAMBRA photometric system
This paper presents the characterization of the optical range of the ALHAMBRA
photometric system, a 20 contiguous, equal-width, medium-band CCD system with
wavelength coverage from 3500A to 9700A. The photometric description of the
system is done by presenting the full response curve as a product of the
filters, CCD and atmospheric transmission curves, and using some first and
second order moments of this response function. We also introduce the set of
standard stars that defines the system, formed by 31 classic spectrophotometric
standard stars which have been used in the calibration of other known
photometric systems, and 288 stars, flux calibrated homogeneously, from the
Next Generation Spectral Library (NGSL). Based on the NGSL, we determine the
transformation equations between Sloan Digital Sky Survey (SDSS) ugriz
photometry and the ALHAMBRA photometric system, in order to establish some
relations between both systems. Finally we develop and discuss a strategy to
calculate the photometric zero points of the different pointings in the
ALHAMBRA project.Comment: Astronomical Journal on the 14th of January 201
Spin precession and spin Hall effect in monolayer graphene/Pt nanostructures
Spin Hall effects have surged as promising phenomena for spin logics
operations without ferromagnets. However, the magnitude of the detected
electric signals at room temperature in metallic systems has been so far
underwhelming. Here, we demonstrate a two-order of magnitude enhancement of the
signal in monolayer graphene/Pt devices when compared to their fully metallic
counterparts. The enhancement stems in part from efficient spin injection and
the large resistivity of graphene but we also observe 100% spin absorption in
Pt and find an unusually large effective spin Hall angle of up to 0.15. The
large spin-to-charge conversion allows us to characterise spin precession in
graphene under the presence of a magnetic field. Furthermore, by developing an
analytical model based on the 1D diffusive spin-transport, we demonstrate that
the effective spin-relaxation time in graphene can be accurately determined
using the (inverse) spin Hall effect as a means of detection. This is a
necessary step to gather full understanding of the consequences of spin
absorption in spin Hall devices, which is known to suppress effective spin
lifetimes in both metallic and graphene systems.Comment: 14 pages, 6 figures. Accepted in 2D Materials.
https://doi.org/10.1088/2053-1583/aa882
Environmental impacts on the Galapagos Islands: identification of interactions, perceptions and steps forward
The ALHAMBRA Project: A large area multi medium-band optical and NIR photometric survey
(ABRIDGED) We describe the first results of the ALHAMBRA survey which
provides cosmic tomography of the evolution of the contents of the Universe
over most of Cosmic history. Our approach employs 20 contiguous, equal-width,
medium-band filters covering from 3500 to 9700 A, plus the JHKs bands, to
observe an area of 4 sqdeg on the sky. The optical photometric system has been
designed to maximize the number of objects with accurate classification by SED
and redshift, and to be sensitive to relatively faint emission lines. The
observations are being carried out with the Calar Alto 3.5m telescope using the
cameras LAICA and O-2000. The first data confirm that we are reaching the
expected magnitude limits of AB<~25 mag in the optical filters from the blue to
8300 A, and from AB=24.7 to 23.4 for the redder ones. The limit in the NIR is
(Vega) K_s~20, H~21, J~22. We expect to obtain accurate redshift values, Delta
z/(1+z) <~ 0.03 for about 5x10^5 galaxies with I<~25 (60% complete), and
z_med=0.74. This accuracy, together with the homogeneity of the selection
function, will allow for the study of the redshift evolution of the large scale
structure, the galaxy population and its evolution with redshift, the
identification of clusters of galaxies, and many other studies, without the
need for any further follow-up. It will also provide targets for detailed
studies with 10m-class telescopes. Given its area, spectral coverage and its
depth, apart from those main goals, the ALHAMBRA-Survey will also produce
valuable data for galactic studies.Comment: Accepted to the Astronomical Journal. 43 pages, 18 figures. The
images have been reduced in resolution to adapt to standard file sizes.
Readers can find the full-resolution version of the paper at the ALHAMBRA web
site (http://www.iaa.es/alhambra) under the "Publications" lin
Exact solution of the two-dimensional Dirac oscillator
In the present article we have found the complete energy spectrum and the
corresponding eigenfunctions of the Dirac oscillator in two spatial dimensions.
We show that the energy spectrum depends on the spin of the Dirac particle.Comment: revtex, 6pp. IVIC-CFLE 93/0
LensPerfect: Gravitational Lens Massmap Reconstructions Yielding Exact Reproduction of All Multiple Images
We present a new approach to gravitational lens massmap reconstruction. Our
massmap solutions perfectly reproduce the positions, fluxes, and shears of all
multiple images. And each massmap accurately recovers the underlying mass
distribution to a resolution limited by the number of multiple images detected.
We demonstrate our technique given a mock galaxy cluster similar to Abell 1689
which gravitationally lenses 19 mock background galaxies to produce 93 multiple
images. We also explore cases in which far fewer multiple images are observed,
such as four multiple images of a single galaxy. Massmap solutions are never
unique, and our method makes it possible to explore an extremely flexible range
of physical (and unphysical) solutions, all of which perfectly reproduce the
data given. Each reconfiguration of the source galaxies produces a new massmap
solution. An optimization routine is provided to find those source positions
(and redshifts, within uncertainties) which produce the "most physical" massmap
solution, according to a new figure of merit developed here. Our method imposes
no assumptions about the slope of the radial profile nor mass following light.
But unlike "non-parametric" grid-based methods, the number of free parameters
we solve for is only as many as the number of observable constraints (or
slightly greater if fluxes are constrained). For each set of source positions
and redshifts, massmap solutions are obtained "instantly" via direct matrix
inversion by smoothly interpolating the deflection field using a recently
developed mathematical technique. Our LensPerfect software is straightforward
and easy to use and is made publicly available via our website.Comment: 17 pages, 18 figures, accepted by ApJ. Software and full-color
version of paper available at http://www.its.caltech.edu/~coe/LensPerfect
Grandes branquiópodos (Crustacea: Branchiopoda: Anostraca, Notostraca) en la provincia de Málaga (España) (año hidrológico 2012/2013)
Grans branquiòpodes (Crustacea, Branchiopoda: Anostraca, Notostraca) a la provÃncia de Mà laga, Espanya (any hidrològic 2012/2013)
S'enumeren les cites d'una campanya de mostratge de grans branquiòpodes portada a terme a la provÃncia de Mà laga (Andalusia, sud d'Espanya) que ha permès la detecció de cinc espècies (Branchipus cortesi, Chirocephalus diaphanus, Streptocephalus torvicornis, Triops mauritanicus aggr. i Phallocryptus spinosa) en 90 masses d'aigua mostrejades.Large branchiopods (Crustacea, Branchiopoda, Anostraca, Notostraca) from Málaga province, Spain (2012/2013 hydrological year)
This paper presents the occurrence of the large branchiopods detected during a survey carried out in the province of Málaga (Andalusia, southern Spain). Five species (Branchipus cortesi, Chirocephalus diaphanus, Streptocephalus torvicornis, Triops mauritanicus aggr. and Phallocryptus spinosa) were recorded at 90 sampled wetlands.Se enumeran las citas de una campaña de muestreo de grandes branquiópodos realizada en la provincia de Málaga (AndalucÃa, sur de España) que ha permitido la detección de cinco especies (Branchipus cortesi, Chirocephalus diaphanus, Streptocephalus torvicornis, Triops mauritanicus aggr. y Phallocryptus spinosa) en 90 masas de agua muestreadas
Communications in flexible supervisor for laboratory research in renewable energy
In laboratories new systems are created where researchers hope to obtain improved functions at a reasonable cost. In them, specialists need efficient tools that offer better performance and flexible features. This paper designs and implements a SCADA system for GERA laboratory (Scientific Group for Applied Renewable Energy at the University of Oriente) adjusted to the inherent characteristics of flexibility and functionality required in research centers. All these features are supported in an efficient communication system with the implementation of various protocols and novel solutions for this type of systems for monitoring and control. It verifies and validates the system for formal methods
Searching for galaxy clusters in the VST-KiDS Survey
We present the methods and first results of the search for galaxy clusters in
the Kilo Degree Survey (KiDS). The adopted algorithm and the criterium for
selecting the member galaxies are illustrated. Here we report the preliminary
results obtained over a small area (7 sq. degrees), and the comparison of our
cluster candidates with those found in the RedMapper and SZ Planck catalogues;
the analysis to a larger area (148 sq. degrees) is currently in progress. By
the KiDS cluster search, we expect to increase the completeness of the clusters
catalogue to z = 0.6-0.7 compared to RedMapper.Comment: 5 pages, 4 figures, to be published in the Proceedings of the
Conference "The Universe of Digital Sky Surveys", Naples, November 25-28 201
- …