560 research outputs found

    Flesh on the Bones: Animal Bodies in Atlantic Roundhouses

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    This volume presents the state of research across Europe to illustrate how comparable interpretative frameworks are used by archaeologists working with both prehistoric and historical societies

    Dynamical segregation of galaxies in groups and clusters

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    We have performed a systematic analysis of the dynamics of different galaxy populations in galaxy groups from the 2dFGRS. For this purpose we have combined all the groups into a single system, where velocities v and radius r are expressed adimensionally. We have used several methods to compare the distributions of relative velocities of galaxies with respect to the group centre for samples selected according to their spectral type (as defined by Madgwick et al., 2002), bj band luminosity and B-R colour index. We have found strong segregation effects: spectral type I objects show a statistically narrower velocity distribution than that of galaxies with a substantial star formation activity (type II-IV). Similarly, the same behavior is observed for galaxies with colour index B-R>1 compared to galaxies with B-R<1. Bright (Mb-19) galaxies show the same segregation. It is not important once the sample is restricted to a given spectral type. These effects are particularly important in the central region (Rp<Rvirial/2) and do not have a strong dependence on the mass of the parent group. These trends show a strong correlation between the dynamics of galaxies in groups and star formation rate reflected both by spectral type and by colour index.Comment: 7 pages, 8 figures. Accepted for publication in MNRA

    Measuring Galaxy Environments with Deep Redshift Surveys

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    We study the applicability of several galaxy environment measures (n^th-nearest-neighbor distance, counts in an aperture, and Voronoi volume) within deep redshift surveys. Mock galaxy catalogs are employed to mimic representative photometric and spectroscopic surveys at high redshift (z ~ 1). We investigate the effects of survey edges, redshift precision, redshift-space distortions, and target selection upon each environment measure. We find that even optimistic photometric redshift errors (\sigma_z = 0.02) smear out the line-of-sight galaxy distribution irretrievably on small scales; this significantly limits the application of photometric redshift surveys to environment studies. Edges and holes in a survey field dramatically affect the estimation of environment, with the impact of edge effects depending upon the adopted environment measure. These edge effects considerably limit the usefulness of smaller survey fields (e.g. the GOODS fields) for studies of galaxy environment. In even the poorest groups and clusters, redshift-space distortions limit the effectiveness of each environment statistic; measuring density in projection (e.g. using counts in a cylindrical aperture or a projected n^th-nearest-neighbor distance measure) significantly improves the accuracy of measures in such over-dense environments. For the DEEP2 Galaxy Redshift Survey, we conclude that among the environment estimators tested the projected n^th-nearest-neighbor distance measure provides the most accurate estimate of local galaxy density over a continuous and broad range of scales.Comment: 17 pages including 16 figures, accepted to Ap

    The Spectroscopic Age of 47 Tuc

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    High signal-to-noise integrated spectra of the metal-rich globular cluster 47 Tuc, spanning the H-gamma(HR) and Fe4668 line indices, have been obtained. The combination of these indices has been suggested (Jones & Worthey 1995, ApJ, 446, L31) as the best available mechanism for cleanly separating the age-metallicity degeneracy which hampers the dating of distant, unresolved, elliptical galaxies. For the first time, we apply this technique to a nearby spheroidal system, 47 Tuc, for which independent ages, based upon more established methods, exist. Such an independent test of the technique's suitability has not been attempted before, but is an essential one before its application to more distant, unresolved, stellar populations can be considered valid. Because of its weak series of Balmer lines, relative to model spectra, our results imply a spectroscopic ``age'' for 47 Tuc well in excess of 20 Gyr, at odds with the colour-magnitude diagram age of 14+/-1 Gyr. The derived metal abundance, however, is consistent with the known value. Emission ``fill-in'' of the H-gamma line as the source of the discrepancy cannot be entirely excluded by existing data, although the observational constraints are restrictive.Comment: 17 pages, 4 figures, LaTeX, accepted for publication in The Astronomical Journal, also available at http://casa.colorado.edu/~bgibson/publications.htm

    New Supernova Candidates from SDSS-DR7 of Spectral Survey

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    The letter presents 25 discovered supernova candidates from SDSS-DR7 with our dedicated method, called Sample Decrease, and 10 of them were confirmed by other research groups, and listed in this letter. Another 15 are first discovered including 14 type Ia and one type II based on Supernova Identification (SNID) analysis. The results proved that our method is reliable, and the description of the method and some detailed spectra analysis procedures were also presented in this letter.Comment: 6 pages, 3 figure

    A veritable confusion: use and abuse of isotope analysis in archaeology

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    The expansion of isotope analyses has transformed the study of past migration and mobility, sometimes providing unexpected and intriguing results. This has, in turn, led to media attention (and concomitant misrepresentation) and scepticism from some archaeologists. Such scepticism is healthy and not always without foundation. Isotope analysis is yet to reach full maturity and challenging issues remain, concerning diagenesis, biosphere mapping resolution and knowledge of the drivers of variation. Bold and over-simplistic interpretations have been presented, especially when relying on single isotope proxies, and researchers have at times been accused of following specific agendas. It is therefore vital to integrate archaeological and environmental evidence to support interpretation. Most importantly, the use of multiple isotope proxies is key: isotope analysis is an exclusive approach and therefore single analyses provide only limited resolution. The growth in isotope research has led to a growth in rebuttals and counter-narratives. Such rebuttals warrant the same critical appraisal that is applied to original research, both of evidence for their assertions and the potential for underlying agendas. This paper takes a case study-based approach focusing on pig movements to Neolithic henge complexes to explore the dangers encountered in secondary use of isotope data

    Rings of fire and Grooved Ware settlement at West Kennet, Wiltshire

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    Alasdair Whittle has had a career-long interest in the Neolithic of the Avebury area (Fig. 17.1). In the late 1980s and early 1990s he undertook a major research project in the region to investigate the Neolithic sequence and its environment (Whittle 1993). This included a series of excavations of early Neolithic sites including the causewayed enclosure at Windmill Hill (Whittle et al. 1999), the chambered tomb at Millbarrow (Whittle 1994), and an earthen long barrow at Easton Down (Whittle et al. 1993). A series of trenches were also cut through two palisade enclosures at West Kennet (Whittle 1997). This campaign of new excavation was accompanied by research into the archives of previous investigations, particularly the publication and subsequent dating of Richard Atkinson’s excavation on and within Silbury Hill in 1968–70 (Bayliss et al. 2007a; Whittle 1997) and a reassessment of the date and development of Avebury itself (Pitts and Whittle 1992). The subsequent decades have seen continued work in the Avebury region, given focus by the Archaeological Research Agenda for the Avebury World Heritage site (AAHRG 2001). Alasdair himself has been instrumental in producing refined chronologies for the West Kennet long barrow (Bayliss et al. 2007b) and the causewayed enclosures at Windmill Hill and Knap Hill (Whittle et al. 2011, chapter 3), and in producing synthetic narratives of early Neolithic sites in the region and beyond (Whittle et al. 2007; 2011, chapters 14 and 15). Further understanding of the late Neolithic landscape has been gained through research excavations at the Beckhampton Avenue and Longstones Cove and ditched enclosure (Gillings et al. 2008), and through rescue excavations undertaken in advance of consolidation works at Silbury Hill (Leary et al. 2013a). The latter in particular has done much to improve our understanding of the development and date of Silbury Hill (Marshall et al. 2013; in prep. a; in prep. b), which has been put into context by a recent synthesis of the available scientific dating evidence for the Avebury area by Frances Healy (2016)

    Feasting and mobility in Iron Age Ireland: multi-isotope analysis reveals the vast catchment of Navan Fort, Ulster

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    Navan Fort is an iconic prehistoric Irish ceremonial centre and the legendary capital of Ulster. The fort has produced an exceptional pig-dominated faunal assemblage that also contained a barbary macaque skull. Dating from the 4th to 1st century BC, it is likely to be a ceremonial feasting centre that may have drawn people and their animals from across Ulster and beyond. This study uses a multi-isotope (87Sr/86Sr, ή34S, ή13C, ή15N) approach to identify non-local animals and reconstruct site catchment. New biosphere mapping means that isotope data can be more confidently interpreted and the combination of strontium and sulphur analysis has the potential to estimate origins. In the absence of human remains, fauna provide the best proxy for human movement. Results for the 35 analysed animals are wide-ranging, especially in terms of strontium (0.707–0.715), which has the largest range for an Irish site. Sulphur values are more restricted (13.1‰−17.1‰) but are high in the context of British and Irish data. Results provide clear evidence for animals (and thus people) coming from across Ulster and beyond, demonstrating the site’s wide catchment. Navan Fort was clearly a major ceremonial centre with far-reaching influence and hosted feasts that drew people and animals from afar
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