995 research outputs found

    Cold Dark Matter Halos Must Burn

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    High-quality optical rotation curves for a sample of low-luminosity spirals evidence that the dark halos around galaxies are inconsistent with the output of proper CDM simulations. In fact, dark halos enveloping stellar disks are structures with approximately a constant density out to the optical edges. This is in strong disagreement with the characteristic rho(r) ~ r^(-1.5) CDM regime and severely challenges the "standard" CDM theory, also because the halo density appears to be heated up, at gross variance with the hierarchical evolution of collision-free particles.Comment: 2 figures, definitive version to appear in the Proceedings of the MPA/ESO/MPE/USM Joint Conference: "Lighthouses of the Universe: The Most Luminous Celestial Objects and their use for Cosmology", August 2001, Garching, German

    The Dark Matter Distribution in Disk Galaxies

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    We use high-quality optical rotation curves of 9 low-luminosity disk galaxies to obtain the velocity profile of the surrounding dark matter halos. We find that they increase linearly with radius at least out to the stellar disk edge, implying that, over the entire region where the stars reside, the density of the dark halo is constant. The properties of the halo mass structure found are similar to that claimed for a number of dwarf and low surface brightness galaxies, but provide a more substantial evidence of the discrepancy between the halo mass distribution predicted in standard cold dark matter scenario and those actually detected around galaxies. We find that the density profile proposed by Burkert (1995) reproduces the halo rotation curves, with halo central densities and core radii scaling as ρ0∝r0−2/3\rho_0 \propto r_0^{-2/3}.Comment: 8 pages, 6 figures, MNRAS accepted. New section and figures added, concerning CDM mass models. Minor changes to the rest of the pape

    Secondary radiation from the Pamela/ATIC excess and relevance for Fermi

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    The excess of electrons/positrons observed by the Pamela and ATIC experiments gives rise to a noticeable amount of synchrotron and Inverse Compton Scattering (ICS) radiation when the e^+e^- interact with the Galactic Magnetic Field, and the InterStellar Radiation Field (ISRF). In particular, the ICS signal produced within the WIMP annihilation interpretation of the Pamela/ATIC excess shows already some tension with the EGRET data. On the other hand, 1 yr of Fermi data taking will be enough to rule out or confirm this scenario with a high confidence level. The ICS radiation produces a peculiar and clean "ICS Haze" feature, as well, which can be used to discriminate between the astrophysical and Dark Matter scenarios. This ICS signature is very prominent even several degrees away from the galactic center, and it is thus a very robust prediction with respect to the choice of the DM profile and the uncertainties in the ISRF.Comment: 5 pages, 3 figures; v2: improved figures, enlarged discussion on the gamma signal and data; to appear in ApJ

    Radio constraints on dark matter annihilation in the galactic halo and its substructures

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    Annihilation of Dark Matter usually produces together with gamma rays comparable amounts of electrons and positrons. The e+e- gyrating in the galactic magnetic field then produce secondary synchrotron radiation which thus provides an indirect mean to constrain the DM signal itself. To this purpose, we calculate the radio emission from the galactic halo as well as from its expected substructures and we then compare it with the measured diffuse radio background. We employ a multi-frequency approach using data in the relevant frequency range 100 MHz-100 GHz, as well as the WMAP Haze data at 23 GHz. The derived constraints are of the order =10^{-24} cm3 s^{-1} for a DM mass m_chi=100 GeV sensibly depending however on the astrophysical uncertainties, in particular on the assumption on the galactic magnetic field model. The signal from single bright clumps is instead largely attenuated by diffusion effects and offers only poor detection perspectives.Comment: 12 pages, 7 figures; v2: some references added, some discussions enlarged; matches journal versio

    Alopecia universalis occurring after alemtuzumab treatment for multiple sclerosis. A two-year follow-up of two patients

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    Alopecia Universalis (AU) is the most severe form of Alopecia Areata and is caused by cytotoxic T-cells reacting with follicular autoantigens, producing complete loss of scalp and body hair. Alemtuzumab is a highly efficacious monoclonal antibody used in the treatment of Multiple Sclerosis (MS), but it causes secondary autoimmunity in up to 40% of patients. Many factors are believed to contribute to this process, but pathogenic mechanisms are not well clear. To date, three cases of AU after treatment with Alemtuzumab have been reported. In this paper we report the cases of two patients who developed AU 12 months after the second cycle of Alemtuzumab, with a review of the literature. One year after the end of the second cycle, two female patients in their thirties experienced complete hair loss. The first case was temporally associated with a significant drop in vitamin D (VD) levels. The second case was accompanied by joint swelling. Both patients had thyroid alterations and showed no hair regrowth after a 2-year follow-up. AU must be considered among the secondary autoimmune manifestations of Alemtuzumab treatment. We emphasize the need for appropriate patient screening and thorough clinical surveillance for factors predisposing patients to secondary autoimmunity

    High Energy Neutrinos with a Mediterranean Neutrino Telescope

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    The high energy neutrino detection by a km^3 Neutrino Telescope placed in the Mediterranean sea provides a unique tool to both determine the diffuse astrophysical neutrino flux and the neutrino-nucleon cross section in the extreme kinematical region, which could unveil the presence of new physics. Here is performed a brief analysis of possible NEMO site performances.Comment: 4 pages, 3 figures, Proceedings of the 30th ICRC 200

    Consumers’ preferences for different energy mixes in Australia

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    Policy makers worldwide face several challenges in addressing climate change, including an understanding of how to successfully introduce initiatives reliant on renewable energy sources (RES). A key component in this is understanding citizen preferences in terms of willingness to pay (WTP). This research focuses on utilising a discrete choice experiment and associated hybrid choice model to model individual WTP for four different RES types (biomass, hydro, solar and wind) against four current and potential non-RES types (gas, oil, nuclear and coal). The model accounts for latent segments in relation to WTP based on pro-environmental attitudes and various socio-demographics. The research examines the case of Australia, but reports on WTP at each state and territory level rather than at the national level. The findings indicate that respondents from different states and territories have heterogeneous preferences in terms of energy mix composition, which led to different WTP values. A large dissonance emerges also comparing preferences at national and state/territory level, which may potentially act as hindrance to the achievement of the goal set for the Paris agreement
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