1,534 research outputs found
CMB signal in WMAP 3yr data with FastICA
We present an application of the fast Independent Component Analysis
(FastICA) to the WMAP 3yr data with the goal of extracting the CMB signal. We
evaluate the confidence of our results by means of Monte Carlo simulations
including CMB, foreground contaminations and instrumental noise specific of
each WMAP frequency band. We perform a complete analysis involving all or a
subset of the WMAP channels in order to select the optimal combination for CMB
extraction, using the frequency scaling of the reconstructed component as a
figure of merit. We found that the combination KQVW provides the best CMB
frequency scaling, indicating that the low frequency foreground contamination
in Q, V and W bands is better traced by the emission in the K band. The CMB
angular power spectrum is recovered up to the degree scale, it is consistent
within errors for all WMAP channel combination considered, and in close
agreement with the WMAP 3yr results. We perform a statistical analysis of the
recovered CMB pattern, and confirm the sky asymmetry reported in several
previous works with independent techniques.Comment: 10 pages, 7 figures, submitted to MNRA
New insights into foreground analysis of the WMAP five-year data using FASTICA
In this paper, we present a foreground analysis of the WMAP 5-year data using
the FASTICA algorithm, improving on the treatment of the WMAP 3-year data in
Bottino et al 2008. We revisit the nature of the free-free spectrum with the
emphasis on attempting to confirm or otherwise the spectral feature claimed in
Dobbler et al 2008b and explained in terms of spinning dust emission in the
warm ionised medium. With the application of different Galactic cuts, the index
is always flatter than the canonical value of 2.14 except for the Kp0 mask
which is steeper. Irrespective of this, we can not confirm the presence of any
feature in the free-free spectrum. We experiment with a more extensive approach
to the cleaning of the data, introduced in connection with the iterative
application of FASTICA. We confirm the presence of a residual foreground whose
spatial distribution is concentrated along the Galactic plane, with pronounced
emission near the Galactic center. This is consistent with the WMAP haze
detected in Finkbeiner 2004. Finally, we attempted to perform the same analysis
on full-sky maps. The code returns good results even for those regions where
the cross-talk among the components is high. However, slightly better results
in terms of the possibility of reconstructing a full-sky CMB map, are achieved
with a simultaneous analysis of both the five WMAP maps and foreground
templates. Nonetheless, some residuals are still present and detected in terms
of an excess in the CMB power spectrum, on small angular scales. Therefore, a
minimal mask for the brightest regions of the plane is necessary, and has been
defined.Comment: Accepted for publication in MNRAS, 25 pages, 17 figures, 4 tables.
Version with full resolution figures available at:
http://www.mpa-garching.mpg.de/~bottino/downloads/bottino_etal.pd
Full Sky Study of Diffuse Galactic Emission at Decimeter Wavelengths
A detailed knowledge of the Galactic radio continuum is of high interest for
studies of the dynamics and structure of the Galaxy as well as for the problem
of foreground removal in Cosmic Microwave Background measurements. In this work
we present a full-sky study of the diffuse Galactic emission at frequencies of
few GHz, where synchrotron radiation is by far the dominant component. We
perform a detailed combined analysis of the extended surveys at 408, 1420 and
2326 MHz (by Haslam et al. 1982, Reich 1982, Reich & Reich, 1986 and Jonas et
al. 1998, respectively). Using the technique applied by Schlegel et al. (1998)
to the IRAS data, we produce destriped versions of the three maps. This allows
us to construct a nearly-full-sky map of the spectral index and of the
normalization factor with sub-degree angular resolution. The resulting
distribution of the spectral indices has an average of beta = 2.695 and
dispersion sigma_{beta} = 0.120. This is representative for the Galactic
diffuse synchrotron emission, with only minor effects from free-free emission
and point sources.Comment: 10 pages, 16 jpeg figures, accepted to Astronomy & Astrophysics,
Comments and figure adde
Prácticas de bioseguridad adoptadas en grandes explotaciones de bovinos de carne de la zona Central de Chile
Bioseguridad se refiere al conjunto de acciones implementadas, orientadas a prevenir el ingreso y salida de agentes causantes de enfermedades en un área que se intenta proteger, así como también limitar su diseminación al interior de esta unidad. El objetivo de este estudio fue definir especificaciones técnicas de bioseguridad predial para rebaños de bovinos de carne y determinar el nivel de cumplimiento de estas prácticas en explotaciones de bovinos de carne de la zona central. Para ello se elaboró un Protocolo de Bioseguridad Predial, compuesto de 80 especificaciones técnicas. Este Protocolo fue evaluado mediante la aplicación de una encuesta en 10 planteles bovinos de producción de carne de ciclo completo con una masa superior a 1000 animales, ubicados en las regiones Quinta, Metropolitana y Sexta. La información obtenida se analizó en forma descriptiva y los resultados fueron expresados en porcentajes de cumplimiento. Los resultados obtenidos de este estudio indicaron que el 50,2% de las especificaciones técnicas de bioseguridad descritas son aplicadas. El mayor nivel de cumplimiento se observó en la prevención de la diseminación de agentes causantes de enfermedades (64,8%), observándose la aplicación de programas de vacunación y control de parásitos en la totalidad de los planteles. En la prevención de la salida de agentes causantes de enfermedades, se registró un nivel de cumplimiento del 40%, detectándose como prácticas habituales el envío de animales enfermos hacia otros planteles. Se observó una reducida implementación de prácticas destinadas a prevenir el ingreso de agentes causantes de enfermedades (45,7%), en especial en el ingreso de personas al plantel. Se concluye que las explotaciones de bovinos de carne evaluadas tienen riesgo de introducir y diseminar agentes causantes de enfermedades que pueden afectar la salud animal y alterar la seguridad y calidad de un producto alimenticio
Anisotropies of the Cosmic Microwave Background
We review the present status of Cosmic Microwave Background (CMB) anisotropy
observations and discuss the main related astrophysical issues, instrumental
effects and data analysis techniques. We summarise the balloon-borne and
ground-based experiments that, after COBE-DMR, yielded detection or significant
upper limits to CMB fluctuations. A comparison of subsets of combined data
indicates that the acoustic features observed today in the angular power
spectrum are not dominated by undetected systematics. Pushing the accuracy of
CMB anisotropy measurements to their ultimate limits represents one of the best
opportunities for cosmology to develop into a precision science in the next
decade. We discuss the forthcoming sub-orbital and space programs, as well as
future prospects of CMB observations.Comment: 83 pages, 16 figures. Revised version, accepted by "La Rivista del
Nuovo Cimento
Effect of Fourier filters in removing periodic systematic effects from CMB data
We consider the application of high-pass Fourier filters to remove periodic
systematic fluctuations from full-sky survey CMB datasets. We compare the
filter performance with destriping codes commonly used to remove the effect of
residual 1/f noise from timelines. As a realistic working case, we use
simulations of the typical Planck scanning strategy and Planck Low Frequency
Instrument noise performance, with spurious periodic fluctuations that mimic a
typical thermal disturbance. We show that the application of Fourier high-pass
filters in chunks always requires subsequent normalisation of induced offsets
by means of destriping. For a complex signal containing all the astrophysical
and instrumental components, the result obtained by applying filter and
destriping in series is comparable to the result obtained by destriping only,
which makes the usefulness of Fourier filters questionable for removing this
kind of effects.Comment: 10 pages, 8 figures, published in Astronomy & Astrophysic
Characterization of the Hamamatsu R11265-103-M64 multi-anode photomultiplier tube
The aim of this paper is to fully characterize the new multi-anode
photomultiplier tube R11265-103-M64, produced by Hamamatsu. Its high effective
active area (77%), its pixel size, the low dark signal rate and the capability
to detect single photon signals make this tube suitable for an application in
high energy physics, such as for RICH detectors. Four tubes and two different
bias voltage dividers have been tested. The results of a standard
characterization of the gain and the anode uniformity, the dark signal rate,
the cross-talk and the device behaviour as a function of temperature have been
studied. The behaviour of the tube is studied in a longitudinal magnetic field
up to 100 Gauss. Shields made of a high permeability material are also
investigated. The deterioration of the device performance due to long time
operation at intense light exposure is studied. A quantitative analysis of the
variation of the gain and the dark signals rate due to the aging is described.Comment: 22 page
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