2,971 research outputs found
Atmospheric Calorimetry above 10 eV: Shooting Lasers at the Pierre Auger Cosmic-Ray Observatory
The Pierre Auger Cosmic-Ray Observatory uses the earth's atmosphere as a
calorimeter to measure extensive air-showers created by particles of
astrophysical origin. Some of these particles carry joules of energy. At these
extreme energies, test beams are not available in the conventional sense. Yet
understanding the energy response of the observatory is important. For example,
the propagation distance of the highest energy cosmic-rays through the cosmic
microwave background radiation (CMBR) is predicted to be strong function of
energy. This paper will discuss recently reported results from the observatory
and the use of calibrated pulsed UV laser "test-beams" that simulate the
optical signatures of ultra-high energy cosmic rays. The status of the much
larger 200,000 km companion detector planned for the northern hemisphere
will also be outlined.Comment: 6 pages, 11 figures XIII International Conference on Calorimetry in
High Energy Physic
A Window On The Earliest Star Formation: Extreme Photoionization Conditions of a High-Ionization, Low-Metallicity Lensed Galaxy at z~2
We report new observations of SL2SJ021737-051329, a lens system consisting of
a bright arc at z=1.84435, magnified ~17x by a massive galaxy at z=0.65.
SL2SJ0217 is a low-mass (M <10^9 M*), low-metallicity (Z~1/20 Z*) galaxy, with
extreme star-forming conditions that produce strong nebular UV emission lines
in the absence of any apparent outflows. Here we present several notable
features from rest-frame UV Keck/LRIS spectroscopy: (1) Very strong narrow
emission lines are measured for CIV 1548,1550, HeII 1640, OIII] 1661,1666,
SiIII] 1883,1892, and CIII] 1907,1909. (2) Double-peaked LyA emission is
observed with a dominant blue peak and centered near the systemic velocity. (3)
The low- and high-ionization absorption features indicate very little or no
outflowing gas along the sightline to the lensed galaxy. The relative emission
line strengths can be reproduced with a very high-ionization, low-metallicity
starburst with binaries, with the exception of He \ii, which indicates an
additional ionization source is needed. We rule out large contributions from
AGN and shocks to the photoionization budget, suggesting that the emission
features requiring the hardest radiation field likely result from extreme
stellar populations that are beyond the capabilities of current models.
Therefore, SL2S0217 serves as a template for the extreme conditions that are
important for reionization and thought to be more common in the early Universe.Comment: 28 pages, 16 figures, 8 tables, re-submitted to ApJ, comments welcom
A Three-Point Cosmic Ray Anisotropy Method
The two-point angular correlation function is a traditional method used to
search for deviations from expectations of isotropy. In this paper we develop
and explore a statistically descriptive three-point method with the intended
application being the search for deviations from isotropy in the highest energy
cosmic rays. We compare the sensitivity of a two-point method and a
"shape-strength" method for a variety of Monte-Carlo simulated anisotropic
signals. Studies are done with anisotropic source signals diluted by an
isotropic background. Type I and II errors for rejecting the hypothesis of
isotropic cosmic ray arrival directions are evaluated for four different event
sample sizes: 27, 40, 60 and 80 events, consistent with near term data
expectations from the Pierre Auger Observatory. In all cases the ability to
reject the isotropic hypothesis improves with event size and with the fraction
of anisotropic signal. While ~40 event data sets should be sufficient for
reliable identification of anisotropy in cases of rather extreme (highly
anisotropic) data, much larger data sets are suggested for reliable
identification of more subtle anisotropies. The shape-strength method
consistently performs better than the two point method and can be easily
adapted to an arbitrary experimental exposure on the celestial sphere.Comment: Fixed PDF erro
Educational studies of cosmic rays with telescope of Geiger-Muller counters
A group of high school students (XII Liceum) in the framework of the Roland
Maze Project has built a compact telescope of three Geiger-Muller counters. The
connection between the telescope and PC computer was also created and programed
by students involved in the Project. This has allowed students to use their
equipment to perform serious scientific measurements concerning the single
cosmic ray muon flux at ground level and below. These measurements were then
analyzed with the programs based on the 'nowadays' knowledge on statistics. An
overview of the apparatus, methods and results were presented at several
students conferences and recently won the first prize in a national competition
of high school students scientific work. The telescope itself, in spite of its
'scientific' purposes, is built in such a way that it is hung on a wall in a
school physics lab and counts muons continuously. This can help to raise the
interest for studying physics among others. At present a few (3) groups of
young participants of the Roland Maze Project have already built their own
telescopes for their schools and some others are working on it. This work is a
perfect example of what can be done by young people when respective
opportunities are created by more experienced researchers and a little help and
advice is given.Comment: 5 figures, 10 page
Lens Galaxy Properties of SBS1520+530: Insights from Keck Spectroscopy and AO Imaging
We report on an investigation of the SBS 1520+530 gravitational lens system
and its environment using archival HST imaging, Keck spectroscopic data, and
Keck adaptive-optics imaging. The AO imaging has allowed us to fix the lens
galaxy properties with a high degree of precision when performing the lens
modeling, and the data indicate that the lens has an elliptical morphology and
perhaps a disk. The new spectroscopic data suggest that previous determinations
of the lens redshift may be incorrect, and we report an updated, though
inconclusive, value z_lens = 0.761. We have also spectroscopically confirmed
the existence of several galaxy groups at approximately the redshift of the
lens system. We create new models of the lens system that explicitly account
for the environment of the lens, and we also include improved constraints on
the lensing galaxy from our adaptive-optics imaging. Lens models created with
these new data can be well-fit with a steeper than isothermal mass slope (alpha
= 2.29, with the density proportional to r^-alpha) if H_0 is fixed at 72
km/s/Mpc; isothermal models require H_0 ~ 50 km/s/Mpc. The steepened profile
may indicate that the lens is in a transient perturbed state caused by
interactions with a nearby galaxy.Comment: 12 pages, 10 figures, submitted to Ap
TeV gamma-UHECR anisotropy by decaying nuclei in flight: first neutrino traces?
Ultra High Cosmic Rays) made by He-like lightest nuclei might solve the AUGER
extragalactic clustering along Cen A. Moreover He like UHECR nuclei cannot
arrive from Virgo because the light nuclei fragility and opacity above a few
Mpc, explaining the Virgo UHECR absence. UHECR signals are spreading along
Cen-A as observed because horizontal galactic arms magnetic fields, bending
them on vertical angles. Cen A events by He-like nuclei are deflected as much
as the observed clustered ones; proton will be more collimated while heavy
(iron) nuclei are too much dispersed. Such a light nuclei UHECR component
coexist with the other Auger heavy nuclei and with the Hires nucleon
composition. Remaining UHECR spread group may hint for correlations with other
gamma (MeV-Al^{26} radioactive) maps, mainly due to galactic SNR sources as
Vela pulsar, the brightest, nearest GeV source. Other nearest galactic gamma
sources show links with UHECR via TeV correlated maps. We suggest that UHECR
are also heavy radioactive galactic nuclei as Ni^{56}, Ni^{57} and Co^{60}
widely bent by galactic fields. UHECR radioactivity (in and
channels) and decay in flight at hundreds keV is boosted (by huge Lorentz
factor (nearly a billion) leading to PeVs electrons and consequent synchrotron
TeVs gamma offering UHECR-TeV correlated sky anisotropy. Moreover also rarest
and non-atmospheric electron and tau neutrinos secondaries at PeVs, as the
first two rarest shower just discovered in ICECUBE, maybe the first signature
of such expected radioactive secondary tail.Comment: 7 pages,3 figures. arXiv admin note: substantial text overlap with
arXiv:1201.015
Origin of atmospheric aerosols at the Pierre Auger Observatory using backward trajectory of air masses
The Pierre Auger Observatory is the largest operating cosmic ray observatory
ever built. Calorimetric measurements of extensive air showers induced by
cosmic rays are performed with a fluorescence detector. Thus, one of the main
challenges is the monitoring of the atmosphere, both in terms of atmospheric
state variables and optical properties. To better understand the atmospheric
conditions, a study of air mass trajectories above the site is presented. Such
a study has been done using an air-modelling program well known in atmospheric
sciences. Its validity has been checked using meteorological radiosonde
soundings performed at the Pierre Auger Observatory. Finally, aerosol
concentration values measured by the Central Laser Facility are compared to
backward trajectories.Comment: 4 pages, 6 figures -- ECRS'12 European Cosmic Ray Symposium (July,
3-7, 2012) at Moscow, Russi
Assessment of left atrial volume before and after pulmonary thromboendarterectomy in chronic thromboembolic pulmonary hypertension.
BackgroundImpaired left ventricular diastolic filling is common in chronic thromboembolic pulmonary hypertension (CTEPH), and recent studies support left ventricular underfilling as a cause. To investigate this further, we assessed left atrial volume index (LAVI) in patients with CTEPH before and after pulmonary thromboendarterectomy (PTE).MethodsForty-eight consecutive CTEPH patients had pre- & post-PTE echocardiograms and right heart catheterizations. Parameters included mean pulmonary artery pressure (mPAP), pulmonary vascular resistance (PVR), cardiac index, LAVI, & mitral E/A ratio. Echocardiograms were performed 6 ± 3 days pre-PTE and 10 ± 4 days post-PTE. Regression analyses compared pre- and post-PTE LAVI with other parameters.ResultsPre-op LAVI (mean 19.0 ± 7 mL/m2) correlated significantly with pre-op PVR (R = -0.45, p = 0.001), mPAP (R = -0.28, p = 0.05) and cardiac index (R = 0.38, p = 0.006). Post-PTE, LAVI increased by 18% to 22.4 ± 7 mL/m2 (p = 0.003). This change correlated with change in PVR (765 to 311 dyne-s/cm5, p = 0.01), cardiac index (2.6 to 3.2 L/min/m2, p = 0.02), and E/A (.95 to 1.44, p = 0.002).ConclusionIn CTEPH, smaller LAVI is associated with lower cardiac output, higher mPAP, and higher PVR. LAVI increases by ~20% after PTE, and this change correlates with changes in PVR and mitral E/A. The rapid increase in LAVI supports the concept that left ventricular diastolic impairment and low E/A pre-PTE are due to left heart underfilling rather than inherent left ventricular diastolic dysfunction
Search for ultrahigh energy neutrinos in highly inclined events at the Pierre Auger Observatory
The Surface Detector of the Pierre Auger Observatory is sensitive to neutrinos of all flavors above 0.1 EeV. These interact through charged and neutral currents in the atmosphere giving rise to extensive air showers. When interacting deeply in the atmosphere at nearly horizontal incidence, neutrinos can be distinguished from regular hadronic cosmic rays by the broad time structure of their shower signals in the water-Cherenkov detectors. In this paper we present for the first time an analysis based on down-going neutrinos. We describe the search procedure, the possible sources of background, the method to compute the exposure and the associated systematic uncertainties. No candidate neutrinos have been found in data collected from 1 January 2004 to 31 May 2010. Assuming an E-2 differential energy spectrum the limit on the single-flavor neutrino is E2dN=dE-7GeVcm-2s-1sr-1 at 90% C.L. in the energy range 1 X 1017eV\u3c E 1020eV
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