132 research outputs found
Planck intermediate results. VIII. Filaments between interacting clusters
About half of the baryons of the Universe are expected to be in the form of
filaments of hot and low density intergalactic medium. Most of these baryons
remain undetected even by the most advanced X-ray observatories which are
limited in sensitivity to the diffuse low density medium. The Planck satellite
has provided hundreds of detections of the hot gas in clusters of galaxies via
the thermal Sunyaev-Zel'dovich (tSZ) effect and is an ideal instrument for
studying extended low density media through the tSZ effect. In this paper we
use the Planck data to search for signatures of a fraction of these missing
baryons between pairs of galaxy clusters. Cluster pairs are good candidates for
searching for the hotter and denser phase of the intergalactic medium (which is
more easily observed through the SZ effect). Using an X-ray catalogue of
clusters and the Planck data, we select physical pairs of clusters as
candidates. Using the Planck data we construct a local map of the tSZ effect
centered on each pair of galaxy clusters. ROSAT data is used to construct X-ray
maps of these pairs. After having modelled and subtracted the tSZ effect and
X-ray emission for each cluster in the pair we study the residuals on both the
SZ and X-ray maps. For the merging cluster pair A399-A401 we observe a
significant tSZ effect signal in the intercluster region beyond the virial
radii of the clusters. A joint X-ray SZ analysis allows us to constrain the
temperature and density of this intercluster medium. We obtain a temperature of
kT = 7.1 +- 0.9, keV (consistent with previous estimates) and a baryon density
of (3.7 +- 0.2)x10^-4, cm^-3. The Planck satellite mission has provided the
first SZ detection of the hot and diffuse intercluster gas.Comment: Accepted by A&
Depression and sickness behavior are Janus-faced responses to shared inflammatory pathways
It is of considerable translational importance whether depression is a form or a consequence of sickness behavior. Sickness behavior is a behavioral complex induced by infections and immune trauma and mediated by pro-inflammatory cytokines. It is an adaptive response that enhances recovery by conserving energy to combat acute inflammation. There are considerable phenomenological similarities between sickness behavior and depression, for example, behavioral inhibition, anorexia and weight loss, and melancholic (anhedonia), physio-somatic (fatigue, hyperalgesia, malaise), anxiety and neurocognitive symptoms. In clinical depression, however, a transition occurs to sensitization of immuno-inflammatory pathways, progressive damage by oxidative and nitrosative stress to lipids, proteins, and DNA, and autoimmune responses directed against self-epitopes. The latter mechanisms are the substrate of a neuroprogressive process, whereby multiple depressive episodes cause neural tissue damage and consequent functional and cognitive sequelae. Thus, shared immuno-inflammatory pathways underpin the physiology of sickness behavior and the pathophysiology of clinical depression explaining their partially overlapping phenomenology. Inflammation may provoke a Janus-faced response with a good, acute side, generating protective inflammation through sickness behavior and a bad, chronic side, for example, clinical depression, a lifelong disorder with positive feedback loops between (neuro)inflammation and (neuro)degenerative processes following less well defined triggers
Planck early results. VI. The High Frequency Instrument data processing
We describe the processing of the 336 billion raw data samples from the High Frequency Instrument (HFI) which we performed to produce six
temperature maps from the first 295 days of Planck-HFI survey data. These maps provide an accurate rendition of the sky emission at 100, 143,
217, 353, 545 and 857GHz with an angular resolution ranging from 9.9 to 4.4 . The white noise level is around 1.5 ÎŒK degree or less in the 3 main
CMB channels (100â217 GHz). The photometric accuracy is better than 2% at frequencies between 100 and 353 GHz and around 7% at the two
highest frequencies. The maps created by the HFI Data Processing Centre reach our goals in terms of sensitivity, resolution, and photometric
accuracy. They are already sufficiently accurate and well-characterised to allow scientific analyses which are presented in an accompanying series
of early papers. At this stage, HFI data appears to be of high quality and we expect that with further refinements of the data processing we should
be able to achieve, or exceed, the science goals of the Planck project
Planck early results. VI. The High Frequency Instrument data processing
We describe the processing of the 336 billion raw data samples from the High
Frequency Instrument (HFI) which we performed to produce six temperature maps
from the first 295 days of Planck-HFI survey data. These maps provide an
accurate rendition of the sky emission at 100, 143, 217, 353, 545 and 857 GHz
with an angular resolution ranging from 9.9 to 4.4^2. The white noise level is
around 1.5 {\mu}K degree or less in the 3 main CMB channels (100--217GHz). The
photometric accuracy is better than 2% at frequencies between 100 and 353 GHz
and around 7% at the two highest frequencies. The maps created by the HFI Data
Processing Centre reach our goals in terms of sensitivity, resolution, and
photometric accuracy. They are already sufficiently accurate and
well-characterised to allow scientific analyses which are presented in an
accompanying series of early papers. At this stage, HFI data appears to be of
high quality and we expect that with further refinements of the data processing
we should be able to achieve, or exceed, the science goals of the Planck
project.Comment: Replaced by the accepted version for publication, as part of a
package of papers describing first results of the Planck mission The paper
with figures at full resolution and full color tables can also be downloaded
from the ESA site http://www.rssd.esa.int/Planc
Planck intermediate results V : Pressure profiles of galaxy clusters from the Sunyaev-Zeldovich effect
This article has an erratum: http://dx.doi.org/10.1051/0004-6361/201220040ePeer reviewe
Planck intermediate results X. Physics of the hot gas in the Coma cluster
We present an analysis of Planck satellite data on the Coma cluster observed via the Sunyaev-Zeldovich effect. Thanks to its great sensitivity, Planck is able, for the first time, to detect SZ emission up to r â 3 Ă R500. We test previously proposed spherically symmetric models for the pressure distribution in clusters against the azimuthally averaged data. In particular, we find that the Arnaud et al. (2010, A&A, 517, A92) "universal" pressure profile does not fit Coma, and that their pressure profile for merging systems provides a reasonable fit to the data only at r R500 than the mean pressure profile predicted by the simulations used to constrain the models. The Planck image shows significant local steepening of the y profile in two regions about half a degree to the west and to the south-east of the cluster centre. These features are consistent with the presence of shock fronts at these radii, and indeed the western feature was previously noticed in the ROSAT PSPC mosaic as well as in the radio. Using Plancky profiles extracted from corresponding sectors we find pressure jumps of 4.9-0.2+0.4 and 5.0-0.1+1.3 in the west and south-east, respectively. Assuming Rankine-Hugoniot pressure jump conditions, we deduce that the shock waves should propagate with Mach number Mw = 2.03-0.04+0.09 and Mse = 2.05-0.02+0.25 in the west and south-east, respectively. Finally, we find that the y and radio-synchrotron signals are quasi-linearly correlated on Mpc scales, with small intrinsic scatter. This implies either that the energy density of cosmic-ray electrons is relatively constant throughout the cluster, or that the magnetic fields fall off much more slowly with radius than previously thought. © 2013 ESO
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