The energy spectrum observed by the AGASA experiment and the spatial distribution of the sources of ultra-high energy cosmic rays

Seven and a half years of continuous monitoring of giant air showers triggered by ultra high-energy cosmic rays have been recently summarized by the AGASA collaboration. The resulting energy spectrum indicates clearly that the cosmic ray spectrum extends well beyond the Greisen-Zatsepin-Kuzmin (GZK) cut-off at $\sim 5 \times 10^{19}$ eV. Furthermore, despite the small number statistics involved, some structure in the spectrum may be emerging. Using numerical simulations, it is demonstrated in the present work that these features are consistent with a spatial distribution of sources that follows the distribution of luminous matter in the local Universe. Therefore, from this point of view, there is no need for a second high-energy component of cosmic rays dominating the spectrum beyond the GZK cut-off.Comment: 14 pages, 4 figures, Astrophys. J. Letters (submitted

Prospects for direct cosmic ray mass measurements through the Gerasimova-Zatsepin effect

The Solar radiation field may break apart ultra high energy cosmic nuclei, after which both remnants will be deflected in the interplanetary magnetic field in different ways. This process is known as the Gerasimova-Zatsepin effect after its discoverers. We investigate the possibility of using the detection of the separated air showers produced by a pair of remnant particles as a way to identify the species of the original cosmic ray primary directly. Event rates for current and proposed detectors are estimated, and requirements are defined for ideal detectors of this phenomenon. Detailed computational models of the disintegration and deflection processes for a wide range of cosmic ray primaries in the energy range of 10^16 to 10^20 eV are combined with sophisticated detector models to calculate realistic detection rates. The fraction of Gerasimova-Zatsepin events is found to be of the order of 10^-5 of the cosmic ray flux, implying an intrinsic event rate of around 0.07 km^-2 sr^-1 yr^-1 in the energy range defined. Event rates in any real experiment, however, existing or under construction, will probably not exceed 10^-2 yr^-1.Comment: 4 pages, 4 figure

Acceptance of fluorescence detectors and its implication in energy spectrum inference at the highest energies

Along the years HiRes and AGASA experiments have explored the fluorescence and the ground array experimental techniques to measure extensive air showers, being both essential to investigate the ultra-high energy cosmic rays. However, such Collaborations have published contradictory energy spectra for energies above the GZK cut-off. In this article, we investigate the acceptance of fluorescence telescopes to different primary particles at the highest energies. Using CORSIKA and CONEX shower simulations without and with the new pre-showering scheme, which allows photons to interact in the Earth magnetic field, we estimate the aperture of the HiRes-I telescope for gammas, iron nuclei and protons primaries as a function of the number of simulated events and primary energy. We also investigate the possibility that systematic differences in shower development for hadrons and gammas could mask or distort vital features of the cosmic ray energy spectrum at energies above the photo-pion production threshold. The impact of these effects on the true acceptance of a fluorescence detector is analyzed in the context of top-down production models

Magnetically Driven Outflows in a Starburst Environment

We here investigate the possibility that the observed collimated outflows in luminous infrared galaxies (LIGs) and some Seyfert galaxies can be produced in a starburst (SB) environment. A nuclear disk can be quickly produced by gas infall during star formation in a rotating, stellar cluster. We find that massive nuclear SBs with core disk masses M_d \sim 10^8 - 10^9 M_{\odot}, and supernova rates \nu_{SN} \simeq 5 \times 10^{-3} - 2 yr^{-1} (which are consistent with the \nu_{SN} values inferred from the observed non-thermal radio power in source candidates) may inject kinetic energies which are high enough to blow out directed flows from the accreting disk surface, within the SB lifetimes. In our models, the acceleration and collimation of the nuclear outflow are provided by magnetic fields anchored into the rotating SB-disk. The emerging outflow carries a kinetic power that is only a small fraction (a few percent) of the supernovae energy rate produced in the SB. Based on conditions determined from observed outflows and disks, we find that moderate disk magnetic fields (\gtrsim 8 \times 10^{-4} G) are able to accelerate the outflows up to the observed terminal velocities (\lesssim few 100 km s^{-1} in the case of the Seyfert galaxies, and \sim 400 - 950 km s^{-1} in the case of the LIGs). The outflow is produced within a wind zone in the disk of radius \lesssim 100 pc in the LIGs, and \lesssim 10 pc in the Seyferts, with wind mass loss to disk accretion rate ratios \dot M_w /\dot M_d \gtrsim 0.1 (where \dot M_d \sim 100 M_{\odot} yr^{-1}). The observation of rotating nuclear disks of gas within few 100 pc scales in source candidates like the LIG Arp 220, and magnetized outflows provide observational support for the picture drawn here.Comment: 31 pages, Latex file, 1 Figure, accepted for publication in the Astrophys. Journa

Intensity-fading and other MS approaches to analyze proteases and protease in inhibitors and their interactions in biological samples

Comunicaciones a congreso

A Magnetized Local Supercluster and the Origin of the Highest Energy Cosmic Rays

A sufficiently magnetized Local Supercluster can explain the spectrum and angular distribution of ultra-high energy cosmic rays. We show that the spectrum of extragalactic cosmic rays with energies below $\sim 10^{20}$ eV may be due to the diffusive propagation in the Local Supercluster with fields of $\sim 10^{-8} - 10^{-7}$ Gauss. Above $\sim 10^{20}$ eV, cosmic rays propagate in an almost rectilinear way which is evidenced by the change in shape of the spectrum at the highest energies. The fit to the spectrum requires that at least one source be located relatively nearby at $\sim 10-15$ Mpc away from the Milky Way. We discuss the origin of magnetic fields in the Local Supercluster and the observable predictions of this model.Comment: 11 pages, 2 figures, submitted to PR

The AGASA/SUGAR Anisotropies and TeV Gamma Rays from the Galactic Center: A Possible Signature of Extremely High-energy Neutrons

Recent analysis of data sets from two extensive air shower cosmic ray detectors shows tantalizing evidence of an anisotropic overabundance of cosmic rays towards the Galactic Center (GC) that ``turns on'' around $10^{18}$ eV. We demonstrate that the anisotropy could be due to neutrons created at the Galactic Center through charge-exchange in proton-proton collisions, where the incident, high energy protons obey an $\sim E^{-2}$ power law associated with acceleration at a strong shock. We show that the normalization supplied by the gamma-ray signal from EGRET GC source 3EG J1746-2851 -- ascribed to pp induced neutral pion decay at GeV energies -- together with a very reasonable spectral index of 2.2, predicts a neutron flux at $\sim 10^{18}$ eV fully consistent with the extremely high energy cosmic ray data. Likewise, the normalization supplied by the very recent GC data from the HESS air-Cerenkov telescope at \~TeV energies is almost equally-well compatible with the $\sim 10^{18}$ eV cosmic ray data. Interestingly, however, the EGRET and HESS data appear to be themselves incompatible. We consider the implications of this discrepancy. We discuss why the Galactic Center environment can allow diffusive shock acceleration at strong shocks up to energies approaching the ankle in the cosmic ray spectrum. Finally, we argue that the shock acceleration may be occuring in the shell of Sagittarius A East, an unusual supernova remnant located very close to the Galactic Center. If this connection between the anisotropy and Sagittarius A East could be firmly established it would be the first direct evidence for a particular Galactic source of cosmic rays up to energies near the ankle.Comment: 57 pages, 2 figure