328 research outputs found
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
The pre-launch Planck Sky Model: a model of sky emission at submillimetre to centimetre wavelengths
We present the Planck Sky Model (PSM), a parametric model for the generation
of all-sky, few arcminute resolution maps of sky emission at submillimetre to
centimetre wavelengths, in both intensity and polarisation. Several options are
implemented to model the cosmic microwave background, Galactic diffuse emission
(synchrotron, free-free, thermal and spinning dust, CO lines), Galactic H-II
regions, extragalactic radio sources, dusty galaxies, and thermal and kinetic
Sunyaev-Zeldovich signals from clusters of galaxies. Each component is
simulated by means of educated interpolations/extrapolations of data sets
available at the time of the launch of the Planck mission, complemented by
state-of-the-art models of the emission. Distinctive features of the
simulations are: spatially varying spectral properties of synchrotron and dust;
different spectral parameters for each point source; modeling of the clustering
properties of extragalactic sources and of the power spectrum of fluctuations
in the cosmic infrared background. The PSM enables the production of random
realizations of the sky emission, constrained to match observational data
within their uncertainties, and is implemented in a software package that is
regularly updated with incoming information from observations. The model is
expected to serve as a useful tool for optimizing planned microwave and
sub-millimetre surveys and to test data processing and analysis pipelines. It
is, in particular, used for the development and validation of data analysis
pipelines within the planck collaboration. A version of the software that can
be used for simulating the observations for a variety of experiments is made
available on a dedicated website.Comment: 35 pages, 31 figure
Ultra High Energy Cosmology with POLARBEAR
Observations of the temperature anisotropy of the Cosmic Microwave Background
(CMB) lend support to an inflationary origin of the universe, yet no direct
evidence verifying inflation exists. Many current experiments are focussing on
the CMB's polarization anisotropy, specifically its curl component (called
"B-mode" polarization), which remains undetected. The inflationary paradigm
predicts the existence of a primordial gravitational wave background that
imprints a unique B-mode signature on the CMB's polarization at large angular
scales. The CMB B-mode signal also encodes gravitational lensing information at
smaller angular scales, bearing the imprint of cosmological large scale
structures (LSS) which in turn may elucidate the properties of cosmological
neutrinos. The quest for detection of these signals; each of which is orders of
magnitude smaller than the CMB temperature anisotropy signal, has motivated the
development of background-limited detectors with precise control of systematic
effects. The POLARBEAR experiment is designed to perform a deep search for the
signature of gravitational waves from inflation and to characterize lensing of
the CMB by LSS. POLARBEAR is a 3.5 meter ground-based telescope with 3.8
arcminute angular resolution at 150 GHz. At the heart of the POLARBEAR receiver
is an array featuring 1274 antenna-coupled superconducting transition edge
sensor (TES) bolometers cooled to 0.25 Kelvin. POLARBEAR is designed to reach a
tensor-to-scalar ratio of 0.025 after two years of observation -- more than an
order of magnitude improvement over the current best results, which would test
physics at energies near the GUT scale. POLARBEAR had an engineering run in the
Inyo Mountains of Eastern California in 2010 and will begin observations in the
Atacama Desert in Chile in 2011.Comment: 8 pages, 6 figures, DPF 2011 conference proceeding
α7-Nicotinic Acetylcholine Receptor: Role in Early Odor Learning Preference in Mice
Recently, we have shown that mice with decreased expression of α7-nicotinic acetylcholine receptors (α7) in the olfactory bulb were associated with a deficit in odor discrimination compared to wild-type mice. However, it is unknown if mice with decreased α7-receptor expression also show a deficit in early odor learning preference (ELP), an enhanced behavioral response to odors with attractive value observed in rats. In this study, we modified ELP methods performed in rats and implemented similar conditions in mice. From post-natal days 5–18, wild-type mice were stroked simultaneously with an odor presentation (conditioned odor) for 90 s daily. Control mice were only stroked, exposed to odor, or neither. On the day of testing (P21), mice that were stroked in concert with a conditioned odor significantly investigated the conditioned odor compared to a novel odor, as observed similarly in rats. However, mice with a decrease in α7-receptor expression that were stroked during a conditioned odor did not show a behavioral response to that odorant. These results suggest that decreased α7-receptor expression has a role in associative learning, olfactory preference, and/or sensory processing deficits
Ucma/GRP inhibits phosphate-induced vascular smooth muscle cell calcification via SMAD-dependent BMP signalling
Vascular calcification (VC) is the process of deposition of calcium phosphate crystals in the blood vessel wall, with a central role for vascular smooth muscle cells (VSMCs). VC is highly prevalent in chronic kidney disease (CKD) patients and thought, in part, to be induced by phosphate imbalance. The molecular mechanisms that regulate VC are not fully known. Here we propose a novel role for the mineralisation regulator Ucma/GRP (Upper zone of growth plate and Cartilage Matrix Associated protein/Gla Rich Protein) in phosphate-induced VSMC calcification. We show that Ucma/GRP is present in calcified atherosclerotic plaques and highly expressed in calcifying VSMCs in vitro. VSMCs from Ucma/GRP(-/-) mice showed increased mineralisation and expression of osteo/chondrogenic markers (BMP-2, Runx2, beta-catenin, p-SMAD1/5/8, ALP, OCN), and decreased expression of mineralisation inhibitor MGP, suggesting that Ucma/GRP is an inhibitor of mineralisation. Using BMP signalling inhibitor noggin and SMAD1/5/8 signalling inhibitor dorsomorphin we showed that Ucma/GRP is involved in inhibiting the BMP-2-SMAD1/5/8 osteo/chondrogenic signalling pathway in VSMCs treated with elevated phosphate concentrations. Additionally, we showed for the first time evidence of a direct interaction between Ucma/GRP and BMP-2. These results demonstrate an important role of Ucma/GRP in regulating osteo/chondrogenic differentiation and phosphate-induced mineralisation of VSMCs.NWO ZonMw [MKMD 40-42600-98-13007]; FCT [SFRH/BPD/70277/2010]info:eu-repo/semantics/publishedVersio
Development and characterization of the readout system for POLARBEAR-2
POLARBEAR-2 is a next-generation receiver for precision measurements of the
polarization of the cosmic microwave background (Cosmic Microwave Background
(CMB)). Scheduled to deploy in early 2015, it will observe alongside the
existing POLARBEAR-1 receiver, on a new telescope in the Simons Array on Cerro
Toco in the Atacama desert of Chile. For increased sensitivity, it will feature
a larger area focal plane, with a total of 7,588 polarization sensitive
antenna-coupled Transition Edge Sensor (TES) bolometers, with a design
sensitivity of 4.1 uKrt(s). The focal plane will be cooled to 250 milliKelvin,
and the bolometers will be read-out with 40x frequency domain multiplexing,
with 36 optical bolometers on a single SQUID amplifier, along with 2 dark
bolometers and 2 calibration resistors. To increase the multiplexing factor
from 8x for POLARBEAR-1 to 40x for POLARBEAR-2 requires additional bandwidth
for SQUID readout and well-defined frequency channel spacing. Extending to
these higher frequencies requires new components and design for the LC filters
which define channel spacing. The LC filters are cold resonant circuits with an
inductor and capacitor in series with each bolometer, and stray inductance in
the wiring and equivalent series resistance from the capacitors can affect
bolometer operation. We present results from characterizing these new readout
components. Integration of the readout system is being done first on a small
scale, to ensure that the readout system does not affect bolometer sensitivity
or stability, and to validate the overall system before expansion into the full
receiver. We present the status of readout integration, and the initial results
and status of components for the full array.Comment: Presented at SPIE Astronomical Telescopes and Instrumentation 2014:
Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for
Astronomy VII. Published in Proceedings of SPIE Volume 915
Planck Intermediate Results. IV. The XMM-Newton validation programme for new Planck galaxy clusters
We present the final results from the XMM-Newton validation follow-up of new
Planck galaxy cluster candidates. We observed 15 new candidates, detected with
signal-to-noise ratios between 4.0 and 6.1 in the 15.5-month nominal Planck
survey. The candidates were selected using ancillary data flags derived from
the ROSAT All Sky Survey (RASS) and Digitized Sky Survey all-sky maps, with the
aim of pushing into the low SZ flux, high-z regime and testing RASS flags as
indicators of candidate reliability. 14 new clusters were detected by XMM,
including 2 double systems. Redshifts lie in the range 0.2 to 0.9, with 6
clusters at z>0.5. Estimated M500 range from 2.5 10^14 to 8 10^14 Msun. We
discuss our results in the context of the full XMM validation programme, in
which 51 new clusters have been detected. This includes 4 double and 2 triple
systems, some of which are chance projections on the sky of clusters at
different z. We find that association with a RASS-BSC source is a robust
indicator of the reliability of a candidate, whereas association with a FSC
source does not guarantee that the SZ candidate is a bona fide cluster.
Nevertheless, most Planck clusters appear in RASS maps, with a significance
greater than 2 sigma being a good indication that the candidate is a real
cluster. The full sample gives a Planck sensitivity threshold of Y500 ~ 4 10^-4
arcmin^2, with indication for Malmquist bias in the YX-Y500 relation below this
level. The corresponding mass threshold depends on z. Systems with M500 > 5
10^14 Msun at z > 0.5 are easily detectable with Planck. The newly-detected
clusters follow the YX-Y500 relation derived from X-ray selected samples.
Compared to X-ray selected clusters, the new SZ clusters have a lower X-ray
luminosity on average for their mass. There is no indication of departure from
standard self-similar evolution in the X-ray versus SZ scaling properties.
(abridged)Comment: accepted by A&
Planck Intermediate Results II: Comparison of Sunyaev-Zeldovich measurements from Planck and from the Arcminute Microkelvin Imager for 11 galaxy clusters
A comparison is presented of Sunyaev-Zeldovich measurements for 11 galaxy
clusters as obtained by Planck and by the ground-based interferometer, the
Arcminute Microkelvin Imager. Assuming a universal spherically-symmetric
Generalised Navarro, Frenk & White (GNFW) model for the cluster gas pressure
profile, we jointly constrain the integrated Compton-Y parameter (Y_500) and
the scale radius (theta_500) of each cluster. Our resulting constraints in the
Y_500-theta_500 2D parameter space derived from the two instruments overlap
significantly for eight of the clusters, although, overall, there is a tendency
for AMI to find the Sunyaev-Zeldovich signal to be smaller in angular size and
fainter than Planck. Significant discrepancies exist for the three remaining
clusters in the sample, namely A1413, A1914, and the newly-discovered Planck
cluster PLCKESZ G139.59+24.18. The robustness of the analysis of both the
Planck and AMI data is demonstrated through the use of detailed simulations,
which also discount confusion from residual point (radio) sources and from
diffuse astrophysical foregrounds as possible explanations for the
discrepancies found. For a subset of our cluster sample, we have investigated
the dependence of our results on the assumed pressure profile by repeating the
analysis adopting the best-fitting GNFW profile shape which best matches X-ray
observations. Adopting the best-fitting profile shape from the X-ray data does
not, in general, resolve the discrepancies found in this subset of five
clusters. Though based on a small sample, our results suggest that the adopted
GNFW model may not be sufficiently flexible to describe clusters universally.Comment: update to metadata author list onl
Planck intermediate results. III. The relation between galaxy cluster mass and Sunyaev-Zeldovich signal
We examine the relation between the galaxy cluster mass M and
Sunyaev-Zeldovich (SZ) effect signal D_A^2 Y for a sample of 19 objects for
which weak lensing (WL) mass measurements obtained from Subaru Telescope data
are available in the literature. Hydrostatic X-ray masses are derived from
XMM-Newton archive data and the SZ effect signal is measured from Planck
all-sky survey data. We find an M_WL-D_A^2 Y relation that is consistent in
slope and normalisation with previous determinations using weak lensing masses;
however, there is a normalisation offset with respect to previous measures
based on hydrostatic X-ray mass-proxy relations. We verify that our SZ effect
measurements are in excellent agreement with previous determinations from
Planck data. For the present sample, the hydrostatic X-ray masses at R_500 are
on average ~ 20 per cent larger than the corresponding weak lensing masses, at
odds with expectations. We show that the mass discrepancy is driven by a
difference in mass concentration as measured by the two methods, and, for the
present sample, the mass discrepancy and difference in mass concentration is
especially large for disturbed systems. The mass discrepancy is also linked to
the offset in centres used by the X-ray and weak lensing analyses, which again
is most important in disturbed systems. We outline several approaches that are
needed to help achieve convergence in cluster mass measurement with X-ray and
weak lensing observations.Comment: 19 pages, 9 figures, matches accepted versio
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