560 research outputs found
Flesh on the Bones: Animal Bodies in Atlantic Roundhouses
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
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
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
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
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
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
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 Atkinsonâs excavation on and within Silbury Hill in 1968â70 (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
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, ÎŽ34S, ÎŽ13C, ÎŽ15N) 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 (0.707â0.715), which has the largest range for an Irish site. Sulphur values are more restricted (13.1â°â17.1â°) 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 siteâs 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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Measuring motion with kinematically redundant accelerometer arrays: theory, simulation and implementation
This work presents two schemes of measuring the linear and angular kinematics of a rigid body using a kinematically redundant array of triple-axis accelerometers with potential applications in biomechanics. A novel angular velocity estimation algorithm is proposed and evaluated that can compensate for angular velocity errors using measurements of the direction of gravity. Analysis and discussion of optimal sensor array characteristics are provided. A damped 2 axis pendulum was used to excite all 6 DoF of the a suspended accelerometer array through determined complex motion and is the basis of both simulation and experimental studies. The relationship between accuracy and sensor redundancy is investigated for arrays of up to 100 triple axis (300 accelerometer axes) accelerometers in simulation and 10 equivalent sensors (30 accelerometer axes) in the laboratory test rig. The paper also reports on the sensor calibration techniques and hardware implementation
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