1,392 research outputs found
Microwave ISM Emission Observed by WMAP
We investigate the nature of the diffuse Galactic emission in the Wilkinson
Microwave Anisotropy Probe (WMAP) temperature anisotropy data. Substantial
dust-correlated emission is observed at all WMAP frequencies, far exceeding the
expected thermal dust emission in the lowest frequency channels (23, 33, 41
GHz). The WMAP team (Bennett et al.) interpret this emission as dust-correlated
synchrotron radiation, attributing the correlation to the natural association
of relativistic electrons produced by SNae with massive star formation in dusty
clouds, and deriving an upper limit of 5% on the contribution of Draine &
Lazarian spinning dust at K-band (23 GHz). We pursue an alternative
interpretation that much, perhaps most, of the dust-correlated emission at
these frequencies is indeed spinning dust, and explore the spectral dependence
on environment by considering a few specific objects as well as the full sky
average. Models similar to Draine & Lazarian spinning dust provide a good fit
to the full-sky data. The full-sky fit also requires a significant component
with free-free spectrum uncorrelated with \Halpha, possibly hot (~million K)
gas within 30 degrees of the Galactic center.Comment: ApJ in press (accepted 5 Dec 2003), version 2: corrected typos and
added references. 23 pages, 5 figures, 2 tables. Free-free haze map is
available at http://skymaps.inf
Detecting Dark Matter Annihilation with CMB Polarization : Signatures and Experimental Prospects
Dark matter (DM) annihilation during hydrogen recombination (z ~ 1000) will
alter the recombination history of the Universe, and affect the observed CMB
temperature and polarization fluctuations. Unlike other astrophysical probes of
DM, this is free of the significant uncertainties in modelling galactic
physics, and provides a method to detect and constrain the cosmological
abundances of these particles. We parametrize the effect of DM annihilation as
an injection of ionizing energy at a rate e_{dm}, and argue that this simple
"on the spot'' modification is a good approximation to the complicated
interaction of the annihilation products with the photon-electron plasma.
Generic models of DM do not change the redshift of recombination, but change
the residual ionization after recombination. This broadens the surface of last
scattering, suppressing the temperature fluctuations and enhancing the
polarization fluctuations. We use the temperature and polarization angular
power spectra to measure these deviations from the standard recombination
history, and therefore, indirectly probe DM annihilation. (abridged)Comment: 13 pages, 8 figures, submitted to PR
Realizing Omega-regular Hyperproperties
We studied the hyperlogic HyperQPTL, which combines the concepts of trace
relations and -regularity. We showed that HyperQPTL is very expressive,
it can express properties like promptness, bounded waiting for a grant,
epistemic properties, and, in particular, any -regular property. Those
properties are not expressible in previously studied hyperlogics like HyperLTL.
At the same time, we argued that the expressiveness of HyperQPTL is optimal in
a sense that a more expressive logic for -regular hyperproperties would
have an undecidable model checking problem. We furthermore studied the
realizability problem of HyperQPTL. We showed that realizability is decidable
for HyperQPTL fragments that contain properties like promptness. But still, in
contrast to the satisfiability problem, propositional quantification does make
the realizability problem of hyperlogics harder. More specifically, the
HyperQPTL fragment of formulas with a universal-existential propositional
quantifier alternation followed by a single trace quantifier is undecidable in
general, even though the projection of the fragment to HyperLTL has a decidable
realizability problem. Lastly, we implemented the bounded synthesis problem for
HyperQPTL in the prototype tool BoSy. Using BoSy with HyperQPTL specifications,
we have been able to synthesize several resource arbiters. The synthesis
problem of non-linear-time hyperlogics is still open. For example, it is not
yet known how to synthesize systems from specifications given in branching-time
hyperlogics like HyperCTL.Comment: International Conference on Computer Aided Verification (CAV 2020
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
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