829 research outputs found
Lensed CMB power spectra from all-sky correlation functions
Weak lensing of the CMB changes the unlensed temperature anisotropy and
polarization power spectra. Accounting for the lensing effect will be crucial
to obtain accurate parameter constraints from sensitive CMB observations.
Methods for computing the lensed power spectra using a low-order perturbative
expansion are not good enough for percent-level accuracy. Non-perturbative
flat-sky methods are more accurate, but curvature effects change the spectra at
the 0.3-1% level. We describe a new, accurate and fast, full-sky
correlation-function method for computing the lensing effect on CMB power
spectra to better than 0.1% at l<2500 (within the approximation that the
lensing potential is linear and Gaussian). We also discuss the effect of
non-linear evolution of the gravitational potential on the lensed power
spectra. Our fast numerical code is publicly available.Comment: 16 pages, 4 figures. Changes to match PRD version including new
section on non-linear corrections. CAMB code available at http://camb.info
Development of ultra-light pixelated ladders for an ILC vertex detector
The development of ultra-light pixelated ladders is motivated by the
requirements of the ILD vertex detector at ILC. This paper summarizes three
projects related to system integration. The PLUME project tackles the issue of
assembling double-sided ladders. The SERWIETE project deals with a more
innovative concept and consists in making single-sided unsupported ladders
embedded in an extra thin plastic enveloppe. AIDA, the last project, aims at
building a framework reproducing the experimental running conditions where sets
of ladders could be tested
Rhythmic dynamics and synchronization via dimensionality reduction : application to human gait
Reliable characterization of locomotor dynamics of human walking is vital to understanding the neuromuscular control of human locomotion and disease diagnosis. However, the inherent oscillation and ubiquity of noise in such non-strictly periodic signals pose great challenges to current methodologies. To this end, we exploit the state-of-the-art technology in pattern recognition and, specifically, dimensionality reduction techniques, and propose to reconstruct and characterize the dynamics accurately on the cycle scale of the signal. This is achieved by deriving a low-dimensional representation of the cycles through global optimization, which effectively preserves the topology of the cycles that are embedded in a high-dimensional Euclidian space. Our approach demonstrates a clear advantage in capturing the intrinsic dynamics and probing the subtle synchronization patterns from uni/bivariate oscillatory signals over traditional methods. Application to human gait data for healthy subjects and diabetics reveals a significant difference in the dynamics of ankle movements and ankle-knee coordination, but not in knee movements. These results indicate that the impaired sensory feedback from the feet due to diabetes does not influence the knee movement in general, and that normal human walking is not critically dependent on the feedback from the peripheral nervous system
Measurement of the rate of nu_e + d --> p + p + e^- interactions produced by 8B solar neutrinos at the Sudbury Neutrino Observatory
Solar neutrinos from the decay of B have been detected at the Sudbury
Neutrino Observatory (SNO) via the charged current (CC) reaction on deuterium
and by the elastic scattering (ES) of electrons. The CC reaction is sensitive
exclusively to nu_e's, while the ES reaction also has a small sensitivity to
nu_mu's and nu_tau's. The flux of nu_e's from ^8B decay measured by the CC
reaction rate is
\phi^CC(nu_e) = 1.75 +/- 0.07 (stat)+0.12/-0.11 (sys.) +/- 0.05(theor) x 10^6
/cm^2 s.
Assuming no flavor transformation, the flux inferred from the ES reaction
rate is
\phi^ES(nu_x) = 2.39+/-0.34 (stat.)+0.16}/-0.14 (sys) x 10^6 /cm^2 s.
Comparison of \phi^CC(nu_e) to the Super-Kamiokande Collaboration's precision
value of \phi^ES(\nu_x) yields a 3.3 sigma difference, providing evidence that
there is a non-electron flavor active neutrino component in the solar flux. The
total flux of active ^8B neutrinos is thus determined to be 5.44 +/-0.99 x
10^6/cm^2 s, in close agreement with the predictions of solar models.Comment: 6 pages (LaTex), 3 figures, submitted to Phys. Rev. Letter
Detection of non-thermal X-ray emission in the lobes and jets of Cygnus A
This article has been published in Monthly Notices of the Royal Astronomical Society © 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. 21 pages, 8 figuresWe present a spectral analysis of the lobes and X-ray jets of Cygnus A, using more than 2 Ms of observations. The X-ray jets are misaligned with the radio jets and significantly wider. We detect non-thermal emission components in both lobes and jets. For the eastern lobe and jet, we find 1 keV flux densities of nJy and nJy, and photon indices of and respectively. For the western lobe and jet, we find flux densities of nJy and nJy, and photon indices of and respectively. Using these results, we modeled the electron energy distributions of the lobes as broken power laws with age breaks. We find that a significant population of non-radiating particles is required to account for the total pressure of the eastern lobe. In the western lobe, no such population is required and the low energy cutoff to the electron distribution there needs to be raised to obtain pressures consistent with observations. This discrepancy is a consequence of the differing X-ray photon indices, which may indicate that the turnover in the inverse-Compton spectrum of the western lobe is at lower energies than in the eastern lobe. We modeled the emission from both jets as inverse-Compton emission. There is a narrow region of parameter space for which the X-ray jet can be a relic of an earlier active phase, although lack of knowledge about the jet's electron distribution and particle content makes the modelling uncertain.Peer reviewedFinal Published versio
A pan-chromatic view of the galaxy cluster XMMU J1230.3+1339 at z=0.975 - Observing the assembly of a massive system
We present a comprehensive galaxy cluster study of XMMU J1230.3+1339 based on
a joint analysis of X-ray data, optical imaging and spectroscopy observations,
weak lensing results, and radio properties for achieving a detailed
multi-component view of this newly discovered system at z=0.975. We find an
optically very rich and massive system with
M200(4.20.8)10^14 M\sun, Tx5.3(+0.7--0.6)keV,
and Lx(6.50.7)10^44 erg/s, for which various widely used
mass proxies are measured and compared. We have identified multiple
cluster-related components including a central fly-through group close to core
passage with associated marginally extended 1.4GHz radio emission possibly
originating from the turbulent wake region of the merging event. On the cluster
outskirts we see evidence for an on-axis infalling group with a second
Brightest Cluster Galaxy (BCG) and indications for an additional off-axis group
accretion event. We trace two galaxy filaments beyond the nominal cluster
radius and provide a tentative reconstruction of the 3D-accretion geometry of
the system. In terms of total mass, ICM structure, optical richness, and the
presence of two dominant BCG-type galaxies, the newly confirmed cluster XMMU
J1230.3+1339 is likely the progenitor of a system very similar to the local
Coma cluster, differing by 7.6 Gyr of structure evolution.Comment: 26 pages, 14 color figures, accepted for publication in A&
First Neutrino Observations from the Sudbury Neutrino Observatory
The first neutrino observations from the Sudbury Neutrino Observatory are
presented from preliminary analyses. Based on energy, direction and location,
the data in the region of interest appear to be dominated by 8B solar
neutrinos, detected by the charged current reaction on deuterium and elastic
scattering from electrons, with very little background. Measurements of
radioactive backgrounds indicate that the measurement of all active neutrino
types via the neutral current reaction on deuterium will be possible with small
systematic uncertainties. Quantitative results for the fluxes observed with
these reactions will be provided when further calibrations have been completed.Comment: Latex, 7 pages, 10 figures, Invited paper at Neutrino 2000
Conference, Sudbury, Canada, June 16-21, 2000 to be published in the
Proceeding
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&
First simultaneous optical/near-infrared imaging of an X-ray selected, high-redshift cluster of galaxies with GROND: the galaxy population of XMMU J0338.7+0030 at z=1.1
The XMM-Newton Distant Cluster Project is a serendipitous survey for clusters
of galaxies at redshifts z>=0.8 based on deep archival XMM-Newton observations.
... Low-significance candidate high-z clusters are followed up with the
seven-channel imager GROND (Gamma-Ray Burst Optical and Near-Infrared Detector)
that is mounted at a 2m-class telescope. ... The test case is XMMU
J0338.7+0030, suggested to be at z~1.45+/-0.15 from the analysis of the z-H vs
H colour-magnitude diagram obtained from the follow-up imaging. Later VLT-FORS2
spectroscopy enabled us to identify four members, which set this cluster at
z=1.097+/-0.002. To reach a better knowledge of its galaxy population, we
observed XMMU J0338.7+0030 with GROND for about 6 hr. The publicly available
photo-z code le Phare was used. The Ks-band number counts of the non-stellar
sources out of the 832 detected down to z'~26 AB-mag in the 3.9x4.3 square
arcmin region of XMMU J0338.7+0030 imaged at all GROND bands clearly exceed
those computed in deep fields/survey areas at ~20.5 - 22.5 AB-mag. The
photo-z's of the three imaged spectroscopic members yield z=1.12+/-0.09. The
spatial distribution and the properties of the GROND sources with a photo-z in
the range 1.01 - 1.23 confirm the correspondence of the X-ray source with a
galaxy over-density at a significance of at least 4.3 sigma. Candidate members
that are spectro-photometrically classified as elliptical galaxies define a red
locus in the i'-z' vs z' colour-magnitude diagram that is consistent with the
red sequence of the cluster RDCS J0910+5422 at z=1.106. XMMU J0338.7+0030 hosts
also a population of bluer late-type spirals and irregulars. The starbursts
among the photometric members populate both loci, consistently with previous
results. The analysis of the available data set indicates that XMMU
J0338.7+0030 is a low-mass cluster (M_200 ~ 1E14 M_sun) at z=1.1. (Abridged)Comment: accepted for publication in Astronomy & Astrophysics Main Journal, 27
pages, 24 figures, 1 tabl
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