1,775 research outputs found

    Response to comment on 'Amphibian fungal panzootic causes catastrophic and ongoing loss of biodiversity'

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    Lambert et al. question our retrospective and holistic epidemiological assessment of the role of chytridiomycosis in amphibian declines. Their alternative assessment is narrow and provides an incomplete evaluation of evidence. Adopting this approach limits understanding of infectious disease impacts and hampers conservation efforts. We reaffirm that our study provides unambiguous evidence that chytridiomycosis has affected at least 501 amphibian species

    Measurement of the Crab Nebula Spectrum Past 100 TeV with HAWC

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    We present TeV gamma-ray observations of the Crab Nebula, the standard reference source in ground-based gamma-ray astronomy, using data from the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory. In this analysis we use two independent energy-estimation methods that utilize extensive air shower variables such as the core position, shower angle, and shower lateral energy distribution. In contrast, the previously published HAWC energy spectrum roughly estimated the shower energy with only the number of photomultipliers triggered. This new methodology yields a much improved energy resolution over the previous analysis and extends HAWC's ability to accurately measure gamma-ray energies well beyond 100 TeV. The energy spectrum of the Crab Nebula is well fit to a log parabola shape (dNdE=ϕ0(E/7 TeV)−α−ÎČln⁥(E/7 TeV))\left(\frac{dN}{dE} = \phi_0 \left(E/\textrm{7 TeV}\right)^{-\alpha-\beta\ln\left(E/\textrm{7 TeV}\right)}\right) with emission up to at least 100 TeV. For the first estimator, a ground parameter that utilizes fits to the lateral distribution function to measure the charge density 40 meters from the shower axis, the best-fit values are ϕo\phi_o=(2.35±\pm0.04−0.21+0.20^{+0.20}_{-0.21})×\times10−13^{-13} (TeV cm2^2 s)−1^{-1}, α\alpha=2.79±\pm0.02−0.03+0.01^{+0.01}_{-0.03}, and ÎČ\beta=0.10±\pm0.01−0.03+0.01^{+0.01}_{-0.03}. For the second estimator, a neural network which uses the charge distribution in annuli around the core and other variables, these values are ϕo\phi_o=(2.31±\pm0.02−0.17+0.32^{+0.32}_{-0.17})×\times10−13^{-13} (TeV cm2^2 s)−1^{-1}, α\alpha=2.73±\pm0.02−0.02+0.03^{+0.03}_{-0.02}, and ÎČ\beta=0.06±\pm0.01±\pm0.02. The first set of uncertainties are statistical; the second set are systematic. Both methods yield compatible results. These measurements are the highest-energy observation of a gamma-ray source to date.Comment: published in Ap

    J-PLUS: Tools to identify compact planetary nebulae in the Javalambre and southern photometric local universe surveys

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    From the approximately ∌\sim3,500 planetary nebulae (PNe) discovered in our Galaxy, only 14 are known to be members of the Galactic halo. Nevertheless, a systematic search for halo PNe has never been performed. In this study, we present new photometric diagnostic tools to identify compact PNe in the Galactic halo by making use of the novel 12-filter system projects, J-PLUS (Javalambre Photometric Local Universe Survey) and S-PLUS (Southern-Photometric Local Universe Survey). We reconstructed the IPHAS (Isaac Newton Telescope (INT) Photometric Hα{\alpha} Survey of the Northern Galactic Plane) diagnostic diagram and propose four new ones using i) the J-PLUS and S-PLUS synthetic photometry for a grid of photo-ionisation models of halo PNe, ii) several observed halo PNe, as well as iii) a number of other emission-line objects that resemble PNe. All colour-colour diagnostic diagrams are validated using two known halo PNe observed by J-PLUS during the scientific verification phase and the first data release (DR1) of S-PLUS and the DR1 of J-PLUS. By applying our criteria to the DR1s (∌\sim1,190 deg2^2), we identified one PN candidate. However, optical follow-up spectroscopy proved it to be a H II region belonging to the UGC 5272 galaxy. Here, we also discuss the PN and two H II galaxies recovered by these selection criteria. Finally, the cross-matching with the most updated PNe catalogue (HASH) helped us to highlight the potential of these surveys, since we recover all the known PNe in the observed area. The tools here proposed to identify PNe and separate them from their emission-line contaminants proved to be very efficient thanks to the combination of many colours, even when applied -like in the present work- to an automatic photometric search that is limited to compact PNe

    Spatially uninformative sounds increase sensitivity for visual motion change

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    It has recently been shown that spatially uninformative sounds can cause a visual stimulus to pop out from an array of similar distractor stimuli when that sound is presented in temporal proximity to a feature change in the visual stimulus. Until now, this effect has predominantly been demonstrated by using stationary stimuli. Here, we extended these results by showing that auditory stimuli can also improve the sensitivity of visual motion change detection. To accomplish this, we presented moving visual stimuli (small dots) on a computer screen. At a random moment during a trial, one of these stimuli could abruptly move in an orthogonal direction. Participants’ task was to indicate whether such an abrupt motion change occurred or not by making a corresponding button press. If a sound (a short 1,000 Hz tone pip) co-occurred with the abrupt motion change, participants were able to detect this motion change more frequently than when the sound was not present. Using measures derived from signal detection theory, we were able to demonstrate that the effect on accuracy was due to increased sensitivity rather than to changes in response bias
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