6,509 research outputs found

    Dark matter cores in the Fornax and Sculptor dwarf galaxies: joining halo assembly and detailed star formation histories

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    We combine the detailed Star Formation Histories of the Fornax and Sculptor dwarf Spheroidals with the Mass Assembly History of their dark matter (DM) halo progenitors to estimate if the energy deposited by Supernova type II (SNeII) is sufficient to create a substantial DM core. Assuming the efficiency of energy injection of the SNeII into DM particles is Ï”gc=0.05\epsilon_{\rm gc}=0.05, we find that a single early episode, z≳zinfallz \gtrsim z_{\rm infall}, that combines the energy of all SNeII due to explode over 0.5 Gyr, is sufficient to create a core of several hundred parsecs in both Sculptor and Fornax. Therefore, our results suggest that it is energetically plausible to form cores in Cold Dark Matter (CDM) halos via early episodic gas outflows triggered by SNeII. Furthermore, based on CDM merger rates and phase-space density considerations, we argue that the probability of a subsequent complete regeneration of the cusp is small for a substantial fraction of dwarf-size haloes.Comment: ApJL accepted versio

    Firing Up Craft Capital: The renaissance of craft and craft policy in the United Kingdom

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    Firing Up Craft Capital: The renaissance of craft and craft policy in the United Kingdom, This article was accepted for publication on the 23rd June 2015. Final published version published online 20 October 2015.Crafts have recently been experiencing a renaissance. This revitalization sees craft increasingly recognised as a growing industrial sector with benefits linked to educational, cultural and economic development policy agendas. This paper engages with policy debates around the place of craft in the United Kingdom from 2010. Drawing on craft sector perspectives and UK government policy initiatives it situates the disciplines and practices of craft within their institutional support networks, organizational contexts and draws attention to the role of individuals in driving agendas. The paper focuses on the national facing crafts development organizations, the UK Crafts Council and the UK Heritage Crafts Association, alongside recent policy discussion emerging from the UK Department for Business, Innovation and Skills. Recognizing that the legacies of past practice often inform contemporary agendas, the paper explores how the advocacy of craft in the recent past has shaped the place and positioning of craft in contemporary UK politics.This work was supported by the UK Arts and Humanities Research Council under Grant AH/I001778/1

    The habitability of stagnant-lid Earths around dwarf stars

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    The habitability of a planet depends on various factors, such as delivery of water during the formation, the co-evolution of the interior and the atmosphere, as well as the stellar irradiation which changes in time. Since an unknown number of rocky exoplanets may operate in a one-plate convective regime, i.e., without plate tectonics, we aim at understanding under which conditions planets in such a stagnant-lid regime may support habitable surface conditions. Understanding the interaction of the planetary interior and outgassing of volatiles with the atmosphere in combination with the evolution of the host star is crucial to determine the potential habitability. M-dwarf stars in particular possess a high-luminosity pre-main sequence phase which endangers the habitability of planets around them via water loss. We therefore explore the potential of secondary outgassing from the planetary interior to rebuild a water reservoir allowing for habitability at a later stage. We compute the boundaries of the habitable zone around M, K, G, and F-dwarf stars using a 1D cloud-free radiative-convective climate model accounting for the outgassing history of CO2 and H2O from an interior evolution and outgassing model for different interior compositions and stellar luminosity evolutions. The outer edge of the habitable zone strongly depends on the amount of CO2 outgassed from the interior, while the inner edge is mainly determined via the stellar irradiation, as soon as a sufficiently large water reservoir has been outgassed. A build-up of a secondary water reservoir for planets around M-dwarf stars is possible even after severe water loss during the high luminosity pre-main sequence phase as long as some water has been retained within the mantle. Earth-like stagnant-lid planets allow for habitable surface conditions within a continuous habitable zone that is dependent on interior composition.Comment: 15 pages, accepted by A&A, abstract shortene

    An individual-based profitability spectrum for understanding interactions between predators and their prey

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    There is confusion in the animal behaviour literature over the use of the terms ‘toxicity’ and ‘unpalatability’, which are commonly used interchangeably when describing the function of chemical compounds in prey, although these terms describe very different functions. Toxic chemicals cause fitness-reducing harm, whereas unpalatability provides aversive taste but no reduction in fitness. Furthermore, chemical defences are only one aspect of prey profitability. We argue that if predators are maximizing fitness, all prey can be described in terms of their costs and benefits to predators across all currencies, giving each prey item a positive or negative position on a ‘profitability spectrum’. Adaptively foraging predators should be selected to eat only prey with a positive profitability. The context of each predator–prey encounter also alters the profitability of the prey. Given that profitability is a function of the current state of both the predator and the prey individuals, we explain why it should be considered to be an attribute of a particular encounter, in contrast to its present usage as an attribute of a prey species. This individual-centred perspective requires researchers to investigate, through both theoretical models and empirical studies, the complex conditions in which predators and prey meet in real life
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