8,658 research outputs found
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
The First Stray Light Corrected EUV Images of Solar Coronal Holes
Coronal holes are the source regions of the fast solar wind, which fills most
of the solar system volume near the cycle minimum. Removing stray light from
extreme ultraviolet (EUV) images of the Sun's corona is of high astrophysical
importance, as it is required to make meaningful determinations of temperatures
and densities of coronal holes. EUV images tend to be dominated by the
component of the stray light due to the long-range scatter caused by
microroughness of telescope mirror surfaces, and this component has proven very
difficult to measure in pre-flight characterization. In-flight characterization
heretofore has proven elusive due to the fact that the detected image is
simultaneously nonlinear in two unknown functions: the stray light pattern and
the true image which would be seen by an ideal telescope. Using a constrained
blind deconvolution technique that takes advantage of known zeros in the true
image provided by a fortuitous lunar transit, we have removed the stray light
from solar images seen by the EUVI instrument on STEREO-B in all four filter
bands (171, 195, 284, and 304 \AA). Uncertainty measures of the stray light
corrected images, which include the systematic error due to misestimation of
the scatter, are provided. It is shown that in EUVI, stray light contributes up
to 70% of the emission in coronal holes seen on the solar disk, which has
dramatic consequences for diagnostics of temperature and density and therefore
estimates of key plasma parameters such as the plasma \ and ion-electron
collision rates.Comment: Accepted to Astrophysical Journal Letter
Large Area Crop Inventory Experiment (LACIE). Phase 3 direct wheat study of North Dakota
The author has identified the following significant results. The green number and brightness scatter plots, channel plots of radiance values, and visual study of the imagery indicate separability between barley and spring wheat/oats during the wheat mid-heading to mid-ripe stages. In the LACIE Phase 3 North Dakota data set, the separation time is more specifically the wheat soft dough stage. At this time, the barley is ripening, and is therefore, less green and brighter than the wheat. Only 4 of the 18 segments studied indicate separation of barley/other spring small grain, even though 11 of the segments have acquisitions covering the wheat soft dough stage. The remaining seven segments had less than 5 percent barley based on ground truth data
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