2,122 research outputs found
An SZ/X-ray galaxy cluster model and the X-ray follow-up of the Planck clusters
Sunyaev-Zel'dovich (SZ) cluster surveys will become an important cosmological
tool over next few years, and it will be essential to relate these new surveys
to cluster surveys in other wavebands. We present an empirical model of cluster
SZ and X-ray observables constructed to address this question and to motivate,
dimension and guide X-ray follow-up of SZ surveys. As an example application of
the model, we discuss potential XMM-Newton follow-up of Planck clusters.Comment: 4 pages, 5 figures. To appear in the proceedings of the XXXXIIIrd
Rencontres de Morion
GABAergic compensation in connexin36 knock-out mice evident during low-magnesium seizure-like event activity
Gap junctions within the cerebral cortex may facilitate cortical seizure formation by their ability to synchronize electrical activity. To investigate this, one option is to compare wild-type (WT) animals with those lacking the gene for connexin36 (Cx36 KO); the protein that forms neuronal gap junctions between cortical inhibitory cells. However, genetically modified knock-out animals may exhibit compensatory effects; with the risk that observed differences between WT and Cx36 KO animals could be erroneously attributed to Cx36 gap junction effects. In this study we investigated the effect of GABAA-receptor modulation (augmentation with 16 μM etomidate and blockade with 100 μM picrotoxin) on low-magnesium seizure-like events (SLEs) in mouse cortical slices. In WT slices, picrotoxin enhanced both the amplitude (49% increase, p = 0.0006) and frequency (37% increase, p = 0.005) of SLEs; etomidate also enhanced SLE amplitude (18% increase, p = 0.003) but reduced event frequency (25% decrease, p < 0.0001). In Cx36 KO slices, the frequency effects of etomidate and picrotoxin were preserved, but the amplitude responses were abolished. Pre-treatment with the gap junction blocker mefloquin in WT slices did not significantly alter the drug responses, indicating that the reduction in amplitude seen in the Cx36 KO mice was not primarily mediated by their lack of interneuronal gap junctions, but was rather due to pre-existing compensatory changes in these animals. Conclusions from studies comparing seizure characteristics between WT and Cx36 KO mice must be viewed with a degree of caution because of the possible confounding effect of compensatory neurophysiological changes in the genetically modified animals
CARMA observations of massive Planck-discovered cluster candidates at z>0.5 associated with WISE overdensities: Breaking the size-flux degeneracy
We use a Bayesian software package to analyze CARMA-8 data towards 19
unconfirmed Planck SZ-cluster candidates from Rodriguez-Gonzalvez et al.
(2015), that are associated with significant overdensities in WISE. We used two
cluster parameterizations, one based on a (fixed shape) generalized-NFW
pressure profile and another based on a beta-gas-density profile (with varying
shape parameters) to obtain parameter estimates for the nine CARMA-8
SZ-detected clusters. We find our sample is comprised of massive,
Y_{500}=0.0010 \pm 0.0015 arcmin^2, relatively compact, theta_{500}= 3.9 \pm
2.0 arcmin systems. Results from the beta model show that our cluster
candidates exhibit a heterogeneous set of brightness-temperature profiles.
Comparison of Planck and CARMA-8 measurements showed good agreement in Y_{500}
and an absence of obvious biases. We estimated the total cluster mass M_{500}
as a function of z for one of the systems; at the preferred photometric
redshift of 0.5, the derived mass, M_{500} \approx 0.8 \pm 0.2 \times 10^{15}
Msun. Spectroscopic Keck/MOSFIRE data confirmed a galaxy member of one of our
cluster candidates to be at z=0.565. Applying a Planck prior in Y_{500} to the
CARMA-8 results reduces uncertainties for both parameters by a factor >4,
relative to the independent Planck or CARMA-8 measurements. We here demonstrate
a powerful technique to find massive clusters at intermediate z \gtrsim 0.5
redshifts using a cross-correlation between Planck and WISE data, with
high-resolution follow-up with CARMA-8. We also use the combined capabilities
of Planck and CARMA-8 to obtain a dramatic reduction by a factor of several, in
parameter uncertainties.Comment: 26 pages, 8 figures, appearing in MNRAS (responded to referee report
The pre-launch Planck Sky Model: a model of sky emission at millimetre to centimetre wavelengths
Semi-classical Green kernel asymptotics for the Dirac operator
We consider a semi-classical Dirac operator in arbitrary spatial dimensions
with a smooth potential whose partial derivatives of any order are bounded by
suitable constants. We prove that the distribution kernel of the inverse
operator evaluated at two distinct points fulfilling a certain hypothesis can
be represented as the product of an exponentially decaying factor involving an
associated Agmon distance and some amplitude admitting a complete asymptotic
expansion in powers of the semi-classical parameter. Moreover, we find an
explicit formula for the leading term in that expansion.Comment: 46 page
Connexin36 knockout mice display increased sensitivity to pentylenetetrazol-induced seizure-like behaviors
Large-scale synchronous firing of neurons during seizures is modulated by electrotonic coupling between neurons via gap junctions. To explore roles for connexin36 (Cx36) gap junctions in seizures, we examined the seizure threshold of connexin36 knockout (Cx36KO) mice using a pentylenetetrazol (PTZ) model
A Comparison of Algorithms for the Construction of SZ Cluster Catalogues
We evaluate the construction methodology of an all-sky catalogue of galaxy
clusters detected through the Sunyaev-Zel'dovich (SZ) effect. We perform an
extensive comparison of twelve algorithms applied to the same detailed
simulations of the millimeter and submillimeter sky based on a Planck-like
case. We present the results of this "SZ Challenge" in terms of catalogue
completeness, purity, astrometric and photometric reconstruction. Our results
provide a comparison of a representative sample of SZ detection algorithms and
highlight important issues in their application. In our study case, we show
that the exact expected number of clusters remains uncertain (about a thousand
cluster candidates at |b|> 20 deg with 90% purity) and that it depends on the
SZ model and on the detailed sky simulations, and on algorithmic implementation
of the detection methods. We also estimate the astrometric precision of the
cluster candidates which is found of the order of ~2 arcmins on average, and
the photometric uncertainty of order ~30%, depending on flux.Comment: Accepted for publication in A&A: 14 pages, 7 figures. Detailed
figures added in Appendi
A comparison of algorithms for the construction of SZ cluster catalogues
J.-B. Melin et al.We evaluate the construction methodology of an all-sky catalogue of galaxy clusters detected through the Sunyaev-Zel'dovich (SZ) effect. We perform an extensive comparison of twelve algorithms applied to the same detailed simulations of the millimeter and submillimeter sky based on a Planck-like case. We present the results of this >SZ Challenge> in terms of catalogue completeness, purity, astrometric and photometric reconstruction. Our results provide a comparison of a representative sample of SZ detection algorithms and highlight important issues in their application. In our study case, we show that the exact expected number of clusters remains uncertain (about a thousand cluster candidates at |b| > 20 deg with 90% purity) and that it depends on the SZ model and on the detailed sky simulations, and on algorithmic implementation of the detection methods. We also estimate the astrometric precision of the cluster candidates which is found of the order of ~2 arcmin on average, and the photometric uncertainty of about 30%, depending on flux. © ESO, 2012.Peer Reviewe
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