194 research outputs found

    Cómo la libertad entra en la filosofía

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    Inasmuch as the question about being demands an answer as to what is the highest being, any ontology must contain an internal or overt reference to the science of God. I examine the way in which we can freely pursue ontology and how philosophers have understood the relation between freedom and philosophy as a human endeavor

    The e+ e- -> P1 P2 gamma processes close to the Phi peak: toward a model-independent analysis

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    We discuss the general decomposition and possible general parameterizations of the processes e+eγP1P2γe^+ e^- \to \gamma^* \to P_1 P_2 \gamma, where P1P2=π0π0P_1 P_2=\pi^0 \pi^0, π0η\pi^0\eta, or π+π\pi^+\pi^-, for sMΦ\sqrt{s}\approx M_\Phi. Particular attention is devoted to the amplitude where the two pseudoscalar mesons are in a JCP=0++J^{CP}= 0^{++} state, where we propose a general parameterization which should help to shed light on the nature of light scalar mesons.Comment: 12 pages, Late

    A simple prescription for simulating and characterizing gravitational arcs

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    Simple models of gravitational arcs are crucial to simulate large samples of these objects with full control of the input parameters. These models also provide crude and automated estimates of the shape and structure of the arcs, which are necessary when trying to detect and characterize these objects on massive wide area imaging surveys. We here present and explore the ArcEllipse, a simple prescription to create objects with shape similar to gravitational arcs. We also present PaintArcs, which is a code that couples this geometrical form with a brightness distribution and adds the resulting object to images. Finally, we introduce ArcFitting, which is a tool that fits ArcEllipses to images of real gravitational arcs. We validate this fitting technique using simulated arcs and apply it to CFHTLS and HST images of tangential arcs around clusters of galaxies. Our simple ArcEllipse model for the arc, associated to a S\'ersic profile for the source, recovers the total signal in real images typically within 10%-30%. The ArcEllipse+S\'ersic models also automatically recover visual estimates of length-to-width ratios of real arcs. Residual maps between data and model images reveal the incidence of arc substructure. They may thus be used as a diagnostic for arcs formed by the merging of multiple images. The incidence of these substructures is the main factor preventing ArcEllipse models from accurately describing real lensed systems.Comment: 12 pages, 11 figures, accepted for publication in A&

    The first 62 AGN observed with SDSS-IV MaNGA - IV: gas excitation and star-formation rate distributions

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    We present maps of the ionized gas flux distributions, excitation, star-formation rate SFR, surface mass density ΣH+\Sigma_{H+}, and obtain total values of SFR and ionized gas masses {\it M} for 62 Active Galactic Nuclei (AGN) observed with SDSS-IV MaNGA and compare them with those of a control sample of 112 non-active galaxies. The most luminous AGN -- with L(\rm{[OIII]}\lambda 5007) \ge 3.8\times 10^{40}\,\mbox{erg}\,\mbox{s}^{-1}, and those hosted by earlier-type galaxies are dominated by Seyfert excitation within 0.2 effective radius ReR_e from the nucleus, surrounded by LINER excitation or transition regions, while the less luminous and hosted by later-type galaxies show equally frequent LINER and Seyfert excitation within 0.2Re0.2\,R_e. The extent RR of the region ionized by the AGN follows the relation RL([OIII])0.5R\propto\,L(\rm{[OIII]})^{0.5} -- as in the case of the Broad-Line Region. The SFR distribution over the region ionized by hot stars is similar for AGN and controls, while the integrated SFR -- in the range 1031010^{-3}-10\,M_\odot\,yr1^{-1} is also similar for the late-type sub-sample, but higher in the AGN for 75\% of the early-type sub-sample. We thus conclude that there is no signature of AGN quenching star formation in the body of the galaxy in our sample. We also find that 66\% of the AGN have higher ionized gas masses MM than the controls -- in the range 1053×107^5-3\times10^7\,M_\odot -- while 75\% of the AGN have higher ΣH+\Sigma_{H+} within 0.2Re0.2\,R_e than the control galaxies

    The SOAR Gravitational Arc Survey - I: Survey overview and photometric catalogs

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    We present the first results of the SOAR (Southern Astrophysical Research) Gravitational Arc Survey (SOGRAS). The survey imaged 47 clusters in two redshift intervals centered at z=0.27z=0.27 and z=0.55z=0.55, targeting the richest clusters in each interval. Images were obtained in the gg', rr' and ii' bands using the SOAR Optical Imager (SOI), with a median seeing of 0.83, 0.76 and 0.71 arcsec, respectively, in these filters. Most of the survey clusters are located within the Sloan Digital Sky Survey (SDSS) Stripe 82 region and all of them are in the SDSS footprint. Photometric calibration was therefore performed using SDSS stars located in our SOI fields. We reached for galaxies in all fields the detection limits of g23.5g \sim 23.5, r23r \sim 23 and i22.5i \sim 22.5 for a signal-to-noise ratio (S/N) = 3. As a by-product of the image processing, we generated a source catalogue with 19760 entries, the vast majority of which are galaxies, where we list their positions, magnitudes and shape parameters. We compared our galaxy shape measurements to those of local galaxies and concluded that they were not strongly affected by seeing. From the catalogue data, we are able to identify a red sequence of galaxies in most clusters in the lower zz range. We found 16 gravitational arc candidates around 8 clusters in our sample. They tend to be bluer than the central galaxies in the lensing cluster. A preliminary analysis indicates that 10\sim 10% of the clusters have arcs around them, with a possible indication of a larger efficiency associated to the high-zz systems when compared to the low-zz ones. Deeper follow-up images with Gemini strengthen the case for the strong lensing nature of the candidates found in this survey.Comment: 17 pages, 11 figures (most of them multi-panel) MNRAS (2013

    Growth and yield models, assortment type and analysis of deadwood in chestnut coppice

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    Deadwood in forest stands close to old-growthness under Mediterranean conditions in the Italian Peninsula

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    Considering that indicators of old-growth features can vary across the European ecoregions, this paper provides some results to identify the distinctive traits of old-growth forests in the Mediterranean ecoregion. Deadwood occurrence as indicator of naturalness is investigated in some remote forest areas that have developed in absence of anthropogenic disturbance over the past few decades. Eleven study sites across the Italian peninsula were elected and records of deadwood were carried out in 1-ha size plots. Deadwood volume, deadwood types and decay stages were inventoried in the selected sites. The amounts of deadwood indicate a large variability among the investigated forest stands: the total volume ranged between 2 and 143 m3ha-1, with an average of 60 m3ha-1. Lying deadwood is the most abundant component of deadwood in the investigated forests, due to the natural mortality occurring in the stands in relation to the processes established in the last decades. On the contrary, stumps are the less represented type of deadwood in almost all the study areas. All the decay classes are present in each study site. The amount of deadwood in Southern Europe, even if lower than that reported for North and Central European countries, could have a different meaning due to the faster decay occurring in Mediterranean forest ecosystems. For this reason, old-growth features and the characteristics of each indicator should be framed and referred to well-defined climatic and biogeographic contexts. Distinctively, under the conditions here investigated, three main deadwood features prove to characterize forest stands close to old-growthness: a ratio of dead to living wood not lower than 10%; lying deadwood much more abundant than the standing one; large range of deadwood size and decay classes across all the deadwood components
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