6,628 research outputs found
The Birmingham-CfA cluster scaling project - II. Mass composition and distribution
We investigate the spatial distribution of the baryonic and non-baryonic mass
components in a sample of 66 virialized systems. We have used X-ray
measurements to determine the deprojected temperature and density structure of
the intergalactic medium and have employed these to map the underlying
gravitational potential. In addition, we have measured the deprojected spatial
distribution of galaxy luminosity for a subset of this sample, spanning over 2
decades in mass. With this combined X-ray/optical study we examine the scaling
properties of the baryons and address the issue of mass-to-light (M/L) ratio in
groups and clusters of galaxies. We measure a median mass-to-light ratio of 224
h70 M/L (solar) in the rest frame B_j band, in good agreement with other
measurements based on X-ray determined masses. There is no trend in M/L with
X-ray temperature and no significant trend for mass to increase faster than
luminosity: M \propto \L_{B,j}^{1.08 +/- 0.12}. This implied lack of
significant variation in star formation efficiency suggests that gas cooling
cannot be greatly enhanced in groups, unless it drops out to form baryonic dark
matter. Correspondingly, our results indicate that non-gravitational heating
must have played a significant role in establishing the observed departure from
self-similarity in low mass systems. The median baryon fraction for our sample
is 0.162 h70^{-3/2}, which allows us to place an upper limit on the
cosmological matter density, Omega_m <= 0.27 h70^{-1}, in good agreement with
the latest results from WMAP. We find evidence of a systematic trend towards
higher central density concentration in the coolest haloes, indicative of an
early formation epoch and consistent with hierarchical formation models.Comment: 14 pages, 11 figures; published in MNRAS. Corrected mistake in
photometric conversion (equation 2): Bj luminosities increased for A2218,
N2563 & N5846. Conclusions unchange
The Birmingham-CfA cluster scaling project - III: entropy and similarity in galaxy systems
We examine profiles and scaling properties of the entropy of the
intergalactic gas in a sample of 66 virialized systems, ranging in mass from
single elliptical galaxies to rich clusters, for which we have resolved X-ray
temperature profiles. Some of the properties we derive appear to be
inconsistent with any of the models put forward to explain the breaking of
self-similarity in the baryon content of clusters. In particular, the entropy
profiles, scaled to the virial radius, are broadly similar in form across the
sample, apart from a normalization factor which differs from the simple
self-similar scaling with temperature. Low mass systems do not show the large
isentropic cores predicted by preheating models, and the high entropy excesses
reported at large radii in groups by Finoguenov et al (2002) are confirmed, and
found to extend even to moderately rich clusters. We discuss the implications
of these results for the evolutionary history of the hot gas in clusters, and
suggest that preheating may affect the entropy of intracluster gas primarily by
reducing the density of material accreting into groups and clusters along
cosmic filaments.Comment: 13 pages, 8 figures - accepted for publication in MNRA
Richness and Abundance of Carabidae and Staphylinidae (Coleoptera), in Northeastern Dairy Pastures Under Intensive Grazing
Dairy cattle has become popular to dairy farmers in the Northeast looking for management schemes to cut production costs. Carabidae (ground beetles) and Staphylinidae (rove beetles) are indicators of habitat disturbances, such as drainage of wetlands, or grassland for grazing animals, and their monitoring could provide one measure of ecosystem sustainability if intensive management systems expand or intensify in the future. Our objective was assess the abundance and species richness of these two beetle families under intensive grazing throughout Pennsylvania, southern New York and Vermont. We collected 4365 ground beetles (83 species) and 4,027 rove beetles (79 species) by pitfall traps in three years in Pennsylvania. Nine ground beetle species, Amara aenea, Poecilus chalcites, Pterostichus melanarius, Bembidion quadrimaculatum oppositum, Amara familiaris, Poecilus lucublandus, Agonum muelleri, Bembidion obtusum and Bembidion mimus represented 80% of the Carabidae collected.
Five other species were new to Pennsylvania. Four rove beetle species, Philonthus cognatus, Meronera venustula, Amischa analis, and Philonthus various = (carbonarius), comprised 74% of the total Staphylinidae collected. Yearly distributions of the dominant species did not change significantly in the three years with A. aenea and P. cognatus being most abundant every year. A parasitic rove beetle, Aleochara tristis, was recovered for the first time in Pennsylvania and Vermont since its release in the 1960\u27s to control face fly, Musca autumnalis.
Similar results were found in New York and Vermont. We collected 1,984 ground beetles (68 species). Pterostichus melanarius was most abundant. Pterostichus vernalis was detected for the first time in the United States (Vermont). It was previously reported from Montreal, Canada. We collected 843 rove beetles (45 species). Philonthus cognatus was the most abundant rove beetle. In addition, Tachinus corticinus, previously known only from Canada, was discovered for the first time in the United States in Vermont.
Pastures in Pennsylvania were diverse, containing 14 species of forage plants and 17 weed species. Botanical composition was similar in New York and Vermont. Sixteen species of grasses and legumes made up 90% of the plant composition and 36 species of weeds made up the remainder. This diÂverse plant ecosystem may explain the richness of ground and rove beetles in northeastern U.S. pastures because the heterogeneity in the plant population provided additional resources which can support a rich assemblage of beetles. Monitoring richness and abundance of Carabidae and Staphylinidae over three years in Pennsylvania suggests intensive grazing systems are ecoÂlogically sustainable
Hydrodynamic simulations of correlation and scatter in galaxy cluster maps
The two dimensional structure of hot gas in galaxy clusters contains
information about the hydrodynamical state of the cluster, which can be used to
understand the origin of scatter in the thermodynamical properties of the gas,
and to improve the use of clusters to probe cosmology. Using a set of
hydrodynamical simulations, we provide a comparison between various maps
currently employed in the X-ray analysis of merging clusters and those cluster
maps anticipated from forthcoming observations of the thermal
Sunyaev-Zel'dovich effect. We show the following: 1) an X-ray pseudo-pressure,
defined as square root of the soft band X-ray image times the temperature map
is a good proxy for the SZ map; 2) we find that clumpiness is the main reason
for deviation between X-ray pseudo-pressure and SZ maps; 3) the level of
clumpiness can be well characterized by X-ray pseudo-entropy maps. 4) We
describe the frequency of deviation in various maps of clusters as a function
of the amplitude of the deviation. This enables both a comparison to
observations and a comparison to effects of introduction of complex physical
processes into simulation.Comment: 7 pages, A&A in pres
The VOICE Study: Valuing Opinions, Individual Communication and Experience: Building the evidence base for undertaking patient-centred family meetings in palliative care - a mixed methods study
Background: Despite family meetings being widely used to facilitate discussion among patients, families, and clinicians in palliative care, there is limited evidence to support their use. This study aims to assess the acceptability and feasibility of Patient-Centred Family Meetings in specialist inpatient palliative care units for patients, families, and clinicians and determine the suitability and feasibility of validated outcome measures from the patient and family perspectives.
Methods: The study is a mixed-methods quasi-experimental design with pre-planned Patient-Centred Family Meetings at the intervention site. The patient will set the meeting agenda a priori allowing an opportunity for their issues to be prioritised and addressed. At the control site, usual care will be maintained which may include a family meeting. Each site will recruit 20 dyads comprising a terminally ill inpatient and their nominated family member. Pre- and post-test administration of the Distress Thermometer, QUAL-EC, QUAL-E, and Patient Health Questionnaire-4 will assess patient and family distress and satisfaction with quality of life. Patient, family, and clinician interviews post-meeting will provide insights into the meeting feasibility and outcome measures. Recruitment percentages and outcome measure completion will also inform feasibility. Descriptive statistics will summarise pre- and post-meeting data generated by the outcome measures. SPSS will analyse the quantitative data. Grounded theory will guide the qualitative data analysis.
Discussion: This study will determine whether planned Patient-Centred Family Meetings are feasible and acceptable and assess the suitability and feasibility of the outcome measures. It will inform a future phase III randomised controlled trial.
Trial registration: Australian New Zealand Clinical Trials Registry ACTRN12616001083482 on 11 August 201
Spatial information retrieval and geographical ontologies: an overview of the SPIRIT project
A large proportion of the resources available on the world-wide
web refer to information that may be regarded as geographically
located. Thus most activities and enterprises take place in one or
more places on the Earth's surface and there is a wealth of survey
data, images, maps and reports that relate to specific places or
regions. Despite the prevalence of geographical context, existing
web search facilities are poorly adapted to help people find
information that relates to a particular location. When the name of
a place is typed into a typical search engine, web pages that
include that name in their text will be retrieved, but it is likely
that many resources that are also associated with the place may
not be retrieved. Thus resources relating to places that are inside
the specified place may not be found, nor may be places that are
nearby or that are equivalent but referred to by another name.
Specification of geographical context frequently requires the use
of spatial relationships concerning distance or containment for
example, yet such terminology cannot be understood by existing
search engines. Here we provide a brief survey of existing
facilities for geographical information retrieval on the web, before
describing a set of tools and techniques that are being developed
in the project SPIRIT : Spatially-Aware Information Retrieval on
the Internet (funded by European Commission Framework V
Project IST-2001-35047)
The Birmingham-CfA cluster scaling project - I: gas fraction and the M-T relation
We have assembled a large sample of virialized systems, comprising 66 galaxy
clusters, groups and elliptical galaxies with high quality X-ray data. To each
system we have fitted analytical profiles describing the gas density and
temperature variation with radius, corrected for the effects of central gas
cooling. We present an analysis of the scaling properties of these systems and
focus in this paper on the gas distribution and M-T relation. In addition to
clusters and groups, our sample includes two early-type galaxies, carefully
selected to avoid contamination from group or cluster X-ray emission. We
compare the properties of these objects with those of more massive systems and
find evidence for a systematic difference between galaxy-sized haloes and
groups of a similar temperature. We derive a mean logarithmic slope of the M-T
relation within R_200 of 1.84+/-0.06, although there is some evidence of a
gradual steepening in the M-T relation, with decreasing mass. We recover a
similar slope using two additional methods of calculating the mean temperature.
Repeating the analysis with the assumption of isothermality, we find the slope
changes only slightly, to 1.89+/-0.04, but the normalization is increased by
30%. Correspondingly, the mean gas fraction within R_200 changes from
(0.13+/-0.01)h70^-1.5 to (0.11+/-0.01)h70^-1.5, for the isothermal case, with
the smaller fractional change reflecting different behaviour between hot and
cool systems. There is a strong correlation between the gas fraction within
0.3*R_200 and temperature. This reflects the strong (5.8 sigma) trend between
the gas density slope parameter, beta, and temperature, which has been found in
previous work. (abridged)Comment: 27 pages, accepted for publication in MNRAS; uses longtable.sty &
lscape.st
WMAP constraints on the Intra-Cluster Medium
We devise a Monte-Carlo based, optimized filter match method to extract the
thermal Sunyaev-Zel'dovich (SZ) signature of a catalog of 116 low-redshift
X-ray clusters from the first year data release of the Wilkinson Microwave
Anisotropy Probe (WMAP). We detect an over-all amplitude for the SZ signal at
the ~ 8-sigma level, yielding a combined constraint of f_{gas}h = 0.08 +/- 0.01
(ran) +/- 0.01 (sys) on the gas mass fraction of the Intra-Cluster Medium. We
also compile X-ray estimated gas fractions from the literature for our sample,
and find that they are consistent with the SZ estimates at the 2-sigma level,
while both show an increasing trend with X-ray temperature. Nevertheless, our
SZ estimated gas fraction is 30-40% smaller than the concordance LCDM cosmic
average. We also express our observations in terms of the SZ flux-temperature
relation, and compare it with other observations, as well as numerical studies.
Based on its spectral and spatial signature, we can also extract the
microwave point source signal of the clusters at the 3-sigma level, which puts
the average microwave luminosity (at ~ 41 GHz) of bright cluster members (M_K <
-21) at (2.4 +/- 0.8) x 10^{27} h^{-2} erg/s/Hz. Furthermore, we can constrain
the average dark matter halo concentration parameter to c_{vir}=3.4+0.6-0.9,
for clusters with T_x > 5 kev.
Our work serves as an example for how correlation of SZ surveys with cluster
surveys in other frequencies can significantly increase our physical
understanding of the intra-cluster medium.Comment: 34 pages, 6 ps figures, Extended discussion of theoretical
uncertainties, radio sources, and future prospects, Accepted for Publication
in Ap
Water Use Efficiency by Switchgrass Compared to a Native Grass or a Native Grass Alfalfa Mixture
Perennial grass systems are being evaluated as a bioenergy feedstock in the northern Great Plains. Inter-annual and inter-seasonal precipitation variation in this region will require efficient water use to maintain sufficient yield production to support a mature bioenergy industry. Objectives were to evaluate the impact of a MayâJune (early season) and a JulyâAugust (late season) drought on the water use efficiency (WUE), amount of water used, and biomass production in monocultures of switchgrass (Panicum virgatum L.), western wheatgrass (Pascopyrum smithii (Rydb.) Ă. Löve), and a western wheatgrassâalfalfa (Medicago sativa L.) mixture using an automated rainout shelter. WUE was strongly driven by biomass accumulation and ranged from 5.6 to 7.4 g biomass mmâ1 water for switchgrass to 1.06 to 2.07 g biomass mmâ1 water used with western wheatgrass. Timing of water stress affected WUE more in western wheatgrass and the western wheatgrassâalfalfa mixture than switchgrass. Water deficit for the western wheatgrassâalfalfa mixture was 23 % lower than western wheatgrass (P=0.0045) and 31 % lower than switchgrass (P\u3c0.0001) under the MayâJune stress water treatment, while switchgrass had a 37 and 38%greater water deficit than did western wheatgrass or western wheatgrassâalfalfa mixture, respectively (P\u3c0.001) under the JulyâAugust water stress treatment. Water depletion was always greatest in the upper 30 cm. Switchgrass had greater WUE but resulted in greater soil water depletion at the end of the growing season compared to western wheatgrass and a western wheatgrassâ alfalfa mixture which may be a concern under multi-year drought conditions
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