359 research outputs found
Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory
The Pierre Auger Collaboration has reported evidence for anisotropy in the
distribution of arrival directions of the cosmic rays with energies
eV. These show a correlation with the distribution
of nearby extragalactic objects, including an apparent excess around the
direction of Centaurus A. If the particles responsible for these excesses at
are heavy nuclei with charge , the proton component of the
sources should lead to excesses in the same regions at energies . We here
report the lack of anisotropies in these directions at energies above
(for illustrative values of ). If the anisotropies
above are due to nuclei with charge , and under reasonable
assumptions about the acceleration process, these observations imply stringent
constraints on the allowed proton fraction at the lower energies
Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
Data collected by the Pierre Auger Observatory through 31 August 2007 showed
evidence for anisotropy in the arrival directions of cosmic rays above the
Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{eV}. The
anisotropy was measured by the fraction of arrival directions that are less
than from the position of an active galactic nucleus within 75 Mpc
(using the V\'eron-Cetty and V\'eron catalog). An updated
measurement of this fraction is reported here using the arrival directions of
cosmic rays recorded above the same energy threshold through 31 December 2009.
The number of arrival directions has increased from 27 to 69, allowing a more
precise measurement. The correlating fraction is , compared
with expected for isotropic cosmic rays. This is down from the early
estimate of . The enlarged set of arrival directions is
examined also in relation to other populations of nearby extragalactic objects:
galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in
hard X-rays by the Swift Burst Alert Telescope. A celestial region around the
position of the radiogalaxy Cen A has the largest excess of arrival directions
relative to isotropic expectations. The 2-point autocorrelation function is
shown for the enlarged set of arrival directions and compared to the isotropic
expectation.Comment: Accepted for publication in Astroparticle Physics on 31 August 201
Search for First Harmonic Modulation in the Right Ascension Distribution of Cosmic Rays Detected at the Pierre Auger Observatory
We present the results of searches for dipolar-type anisotropies in different
energy ranges above eV with the surface detector array of
the Pierre Auger Observatory, reporting on both the phase and the amplitude
measurements of the first harmonic modulation in the right-ascension
distribution. Upper limits on the amplitudes are obtained, which provide the
most stringent bounds at present, being below 2% at 99% for EeV
energies. We also compare our results to those of previous experiments as well
as with some theoretical expectations.Comment: 28 pages, 11 figure
Assessment of the toll-like receptor 4 Asp299Gly, Thr399Ile and interleukin-8 -251 polymorphisms in the risk for the development of distal gastric cancer
<p>Abstract</p> <p>Background</p> <p>The intensity of the inflammation induced by <it>Helicobacter pylori </it>colonization is associated with the development of distal gastric cancer (GC). The host response to <it>H</it>. <it>pylori </it>has been related to genetic polymorphisms that influence both innate and adaptive immune responses.</p> <p>Our aim was to investigate whether the presence of the <it>TLR4 Asp299Gly</it>, <it>TLR4 Thr399Ile </it>and <it>IL-8-251 </it>A/T polymorphisms had any influence in the development of distal GC in a Mexican population.</p> <p>Methods</p> <p>We studied 337 patients that were divided in two groups: 78 patients with histologically confirmed distal GC and 259 non-cancer controls. The presence of <it>H. pylori </it>in the control population was defined by positive results of at least two of four diagnostic tests: serology, histology, rapid urease test and culture. Human DNA was purified and genotyped for <it>TLR4 Asp299Gly </it>polymorphism by pyrosequencing, for <it>TLR4 Thr399Ile </it>by PCR-RFLP and for <it>IL8-251 </it>by the amplification refractory mutation system (ARMS)-PCR.</p> <p>Results</p> <p>The non-cancer control group was found to be in Hardy-Weinberg equilibrium at the polymorphic loci studied (chi-square <sub>H-W </sub>= 0.58 for <it>IL8-251</it>, 0.42 for <it>TLR4 Asp299Gly </it>and 0.17 for <it>TLR4 Thr399Ile</it>). The frequencies of mutated alleles (homozygous plus heterozygous) were compared between cases and controls. We found no significant difference for <it>TLR4- Asp299Gly </it>[the 7.7% of distal GC patients and 7.7 % non-cancer controls (p = 0.82)] and for <it>TLR4 Thr399Ile </it>[the 1.3% of GC patients and the 5% of the control population (p = 0.2)]. In contrast, for <it>IL-8-251 </it>A/T, 80.77% of the GC patients and 66.4% in the control group age and gender matched had at least one copy of mutated allele (OR = 2.12, 95% CI = 1.1–4.2) (p = 0.023).</p> <p>Conclusion</p> <p>This study showed that the <it>IL8-251*A </it>allele could be related to the development of distal gastric cancer in this Mexican population.</p
DeepZipper: A Novel Deep-learning Architecture for Lensed Supernovae Identification
Large-scale astronomical surveys have the potential to capture data on large numbers of strongly gravitationally lensed supernovae (LSNe). To facilitate timely analysis and spectroscopic follow-up before the supernova fades, an LSN needs to be identified soon after it begins. To quickly identify LSNe in optical survey data sets, we designed ZipperNet, a multibranch deep neural network that combines convolutional layers (traditionally used for images) with long short-term memory layers (traditionally used for time series). We tested ZipperNet on the task of classifying objects from four categories—no lens, galaxy-galaxy lens, lensed Type-Ia supernova, lensed core-collapse supernova—within high-fidelity simulations of three cosmic survey data sets: the Dark Energy Survey, Rubin Observatory’s Legacy Survey of Space and Time (LSST), and a Dark Energy Spectroscopic Instrument (DESI) imaging survey. Among our results, we find that for the LSST-like data set, ZipperNet classifies LSNe with a receiver operating characteristic area under the curve of 0.97, predicts the spectroscopic type of the lensed supernovae with 79% accuracy, and demonstrates similarly high performance for LSNe 1–2 epochs after first detection. We anticipate that a model like ZipperNet, which simultaneously incorporates spatial and temporal information, can play a significant role in the rapid identification of lensed transient systems in cosmic survey experiments
Building an Efficient Cluster Cosmology Software Package for Modeling Cluster Counts and Lensing
We introduce a software suite developed for galaxy cluster cosmological
analysis with the Dark Energy Survey Data. Cosmological analyses based on
galaxy cluster number counts and weak-lensing measurements need efficient
software infrastructure to explore an increasingly large parameter space, and
account for various cosmological and astrophysical effects. Our software
package is designed to model the cluster observables in a wide-field optical
survey, including galaxy cluster counts, their averaged weak-lensing masses, or
the cluster's averaged weak-lensing radial signals. To ensure maximum
efficiency, this software package is developed in C++ in the CosmoSIS software
framework, making use of the CUBA integration library. We also implement a
testing and validation scheme to ensure the quality of the package. We
demonstrate the effectiveness of this development by applying the software to
the Dark Energy Survey Year 1 galaxy cluster cosmological data sets, and
acquired cosmological constraints that are consistent with the fiducial Dark
Energy Survey analysis
The MADPSZ catalogue of Planck clusters over the DES region: extending to lower mass and higher redshift
We present the first systematic follow-up of Planck Sunyaev-Zeldovich effect
(SZE) selected candidates down to signal-to-noise (S/N) of 3 over the 5000
deg covered by the Dark Energy Survey. Using the MCMF cluster confirmation
algorithm, we identify optical counterparts, determine photometric redshifts
and richnesses and assign a parameter, , that reflects the
probability that each SZE-optical pairing represents a real cluster rather than
a random superposition of physically unassociated systems. The new MADPSZ
cluster catalogue consists of 1092 MCMF confirmed clusters and has a purity of
85%. We present the properties of subsamples of the MADPSZ catalogue that have
purities ranging from 90% to 97.5%, depending on the adopted
threshold. halo mass estimates, redshifts, richnesses, and optical
centers are presented for all MADPSZ clusters. The MADPSZ catalogue adds 828
previously unknown Planck identified clusters over the DES footprint and
provides redshifts for an additional 50 previously published Planck selected
clusters with S/N>4.5. Using the subsample with spectroscopic redshifts, we
demonstrate excellent cluster photo- performance with an RMS scatter in
of 0.47%. Our MCMF based analysis allows us to infer the
contamination fraction of the initial S/N>3 Planck selected candidate list,
which is 50%. We present a method of estimating the completeness of the MADPSZ
cluster sample and selected subsamples. In comparison to the
previously published Planck cluster catalogues. this new S/N 3 MCMF
confirmed cluster catalogue populates the lower mass regime at all redshifts
and includes clusters up to z1.3.Comment: 20 pages, 5 Appendices, 17 figures, submitted to MNRA
Ultracool dwarfs candidates based on six years of the Dark Energy Survey data
We present a sample of 19,583 ultracool dwarf candidates brighter than z
selected from the Dark Energy Survey DR2 coadd data matched to VHS
DR6, VIKING DR5 and AllWISE covering 4,800 . The ultracool
candidates were first pre-selected based on their (i-z), (z-Y), and (Y-J)
colours. They were further classified using a method that compares their
optical, near-infrared and mid-infrared colours against templates of M, L and T
dwarfs. 14,099 objects are presented as new L and T candidates and the
remaining objects are from the literature, including 5,342 candidates from our
previous work. Using this new and deeper sample of ultracool dwarf candidates
we also present: 20 new candidate members to nearby young moving groups (YMG)
and associations, variable candidate sources and four new wide binary systems
composed of two ultracool dwarfs. Finally, we also show the spectra of twelve
new ultracool dwarfs discovered by our group and presented here for the first
time. These spectroscopically confirmed objects are a sanity check of our
selection of ultracool dwarfs and photometric classification method.Comment: 18 pages, 10 figures, 7 tables. Accepted for publication in MNRA
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