2,371 research outputs found
CMB Distortions from Superconducting Cosmic Strings
We reconsider the effect of electromagnetic radiation from superconducting
strings on cosmic microwave background (CMB) mu- and y-distortions and derive
present (COBE-FIRAS) and future (PIXIE) constraints on the string tension,
mu_s, and electric current, I. We show that absence of distortions of the CMB
in PIXIE will impose strong constraints on mu_s and I, leaving the possibility
of light strings (G mu_s < 10^{-18}) or relatively weak currents (I < 10 TeV).Comment: 10pages, 5 figures, Submitted to PRD, v2:References added, replaced
to match the PRD versio
Polarization fluctuations due to extragalactic sources
We have derived the relationship between polarization and intensity
fluctuations due to point sources. In the case of a Poisson distribution of a
population with uniform evolution properties and constant polarization degree,
polarization fluctuations are simply equal to intensity fluctuations times the
average polarization degree. Conservative estimates of the polarization degree
of the classes of extragalactic sources contributing to fluctuations in the
frequency ranges covered by the forthcoming space missions MAP and Planck
Surveyor indicate that extragalactic sources will not be a strong limiting
factor to measurements of the polarization of the Cosmic Microwave Background.Comment: 15 pages LaTeX file, 3 postscript figures. Uses elsart.sty and
elsart.cls Accepted for publication in New Astronom
Optical Coherence Tomography Findings in Rhegmatogenous Retinal Detachment: A Systematic Review
Rhegmatogenous retinal detachment is a sight-threatening condition that may lead to blindness if left untreated. Surgical treatments may vary and are tailored to a single patient. Anatomical and functional results may vary, due to factors that are currently under study. Optical coherence tomography (OCT) allows a detailed visualization of the retinal structure. Some studies have been performed using OCT on eyes with retinal detachment. We performed a review on the subject. Several data have been obtained using different OCT applications. Some alterations may represent potential biomarkers since they are associated with visual and anatomical prognoses. Increased knowledge on the subject may be helpful to choose among different surgical strategies and endotamponades. More research on the topic is needed
Cosmological Constraints on Neutrino Injection
We derive general constraints on the relic abundances of a long-lived
particle which mainly decays into a neutrino (and something else) at
cosmological time scales. Such an exotic particle may show up in various
particle-physics models based on physics beyond the standard model. The
constraints are obtained from big-bang nucleosynthesis, cosmic microwave
background and diffuse neutrino and photon fluxes, depending on the lifetime
and the electromagnetic and hadronic branching ratios.Comment: 33 pages, 23 figure
Extragalactic Source Counts and Contributions to the Anisotropies of the Cosmic Microwave Background. Predictions for the Planck Surveyor mission
We present predictions for the counts of extragalactic sources, the
contributions to fluctuations and their spatial power spectrum in each channel
foreseen for the Planck Surveyor (formerly COBRAS/SAMBA) mission. The
contribution to fluctuations due to clustering of both radio and far--IR
sources is found to be generally small in comparison with the Poisson term;
however the relative importance of the clustering contribution increases and
may eventually become dominant if sources are identified and subtracted down to
faint flux limits. The central Planck frequency bands are expected to be
``clean'': at high galactic latitude (|b|>20), where the reduced galactic noise
does not prevent the detection of the extragalactic signal, only a tiny
fraction of pixels is found to be contaminated by discrete extragalactic
sources. Moreover, removal of contaminating signals is eased by the substantial
difference between their power spectrum and that of primordial fluctuations.Comment: 10 pages, Latex, mn.sty, 8 figures included, MNRAS, in the press.
Minor changes in the text. Sections 3.1 and 3.2 have been expanded. Source
counts in Table 2 have been slightly changed. Figure 1,2,7 and 8 have been
replaced by new version
A New Method for ISOCAM Data Reduction - I. Application to the European Large Area ISO Survey Southern Field: Method and Results
We have developed a new data reduction technique for ISOCAM LW data and have
applied it to the European Large Area ISO Survey (ELAIS) LW3 (15 micron)
observations in the southern hemisphere (S1). This method, known as LARI
technique and based on the assumption of the existence of two different time
scales in ISOCAM transients (accounting either for fast or slow detector
response), was particularly designed for the detection of faint sources. In the
ELAIS S1 field we obtained a catalogue of 462 15 micron sources with
signal-to-noise ratio >= 5 and flux densities in the range 0.45 - 150 mJy
(filling the whole flux range between the Deep ISOCAM Surveys and the IRAS
Faint Source Survey). The completeness at different flux levels and the
photometric accuracy of this catalogue have been tested with simulations. Here
we present a detailed description of the method and discuss the results
obtained by its application to the S1 LW3 data.Comment: 20 pages, LaTeX, MNRAS style, 20 postscript figures, full catalogue
not yet available at http://boas5.bo.astro.it/~elais/catalogues/. Accepted
for publication in MNRA
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