2,055 research outputs found
The most massive galaxies in clusters are already fully grown at
By constructing scaling relations for galaxies in the massive cluster
MACSJ0717.5 at and comparing with those of Coma, we model the
luminosity evolution of the stellar populations and the structural evolution of
the galaxies. We calculate magnitudes, surface brightnesses and effective radii
using HST/ACS images and velocity dispersions using Gemini/GMOS spectra, and
present a catalogue of our measurements for 17 galaxies. We also generate
photometric catalogues for galaxies from the HST imaging. With
these, we construct the colour-magnitude relation, the fundamental plane, the
mass-to-light versus mass relation, the mass-size relation and the
mass-velocity dispersion relation for both clusters. We present a new, coherent
way of modelling these scaling relations simultaneously using a simple physical
model in order to infer the evolution in luminosity, size and velocity
dispersion as a function of redshift, and show that the data can be fully
accounted for with this model. We find that (a) the evolution in size and
velocity dispersion undergone by these galaxies between and is mild, with and , and (b) the stellar populations are old, Gyr,
with a Gyr dispersion in age, and are consistent with evolving purely
passively since with . The implication is that these galaxies formed their stars early and
subsequently grew dissipationlessly so as to have their mass already in place
by , and suggests a dominant role for dry mergers, which may have
accelerated the growth in these high-density cluster environments.Comment: 20 pages; accepted for publication in MNRA
Association of the Covid-19 lockdown with smoking, drinking, and attempts to quit in England: an analysis of 2019-2020 data
Aim: To examine changes in smoking, drinking and quitting/reduction behaviour following the COVID‐19 lockdown in
England. Design/setting: Monthly cross‐sectional surveys representative of the adult population in England,
aggregated before (April 2019–February 2020) versus after (April 2020) lockdown. Participants: A total of 20 558
adults (≥ 16 years). Measurements: The independent variable was the timing of the COVID‐19 lockdown (before versus
after March 2020). Dependent variables were: prevalence of smoking and high‐risk drinking, past‐year cessation and quit
attempts (among past‐year smokers), past‐year attempts to reduce alcohol consumption (among high‐risk drinkers) and
use of evidence‐based (e.g. prescription medication/face‐to‐face behavioural support) and remote support [telephone
support/websites/applications (apps)] for smoking cessation and alcohol reduction (among smokers/high‐risk drinkers
who made a quit/reduction attempt). Covariates included age, sex, social grade, region and level of nicotine and alcohol
dependence (as relevant). Findings: The COVID‐19 lockdown was not associated with a significant change in smoking
prevalence [17.0% (after) versus 15.9% (before), odds ratio (OR) = 1.09, 95% CI = 0.95–1.24], but was associated with
increases in quit attempts [39.6 versus 29.1%, adjusted odds ratio (ORadj) = 1.56, 95% CI = 1.23–1.98], quit success
(21.3 versus 13.9%, ORadj = 2.01, 95% CI = 1.22–3.33) and cessation (8.8 versus 4.1%, ORadj = 2.63, 95%
CI = 1.69–4.09) among past‐year smokers. Among smokers who tried to quit, there was no significant change in use
of evidence‐based support (50.0 versus 51.5%, ORadj = 1.10, 95% CI = 0.72–1.68) but use of remote support increased
(10.9 versus 2.7%, ORadj = 3.59, 95% CI = 1.56–8.23). Lockdown was associated with increases in high‐risk drinking
(38.3 versus 25.1%, OR = 1.85, CI = 1.67–2.06), but also alcohol reduction attempts by high‐risk drinkers (28.5 versus
15.3%, ORadj = 2.16, 95% CI = 1.77–2.64). Among high‐risk drinkers who made a reduction attempt, use of
evidence‐based support decreased (1.2 versus 4.0%, ORadj = 0.23, 95% CI = 0.05–0.97) and there was no significant
change in use of remote support (6.9 versus 6.1%, ORadj = 1.32, 95% CI = 0.64–2.75). Conclusions: Following the
March 2020 COVID‐19 lockdown, smokers and high‐risk drinkers in England were more likely than before lockdown to
report trying to quit smoking or reduce alcohol consumption and rates of smoking cessation and use of remote cessation
support were higher. However, high‐risk drinking prevalence increased post‐lockdown and use of evidence‐based support
for alcohol reduction by high‐risk drinkers decreased with no compensatory increase in use of remote support
Pastures from Space - Application of Satellite-Derived Pasture Predictions Improve the Profitability of Australian Sheep Producers
Pastures from Space, a collaborative program between CSIRO Livestock Industries and the Western Australian state Departments of Agriculture and Land Information, has developed the capacity to measure both the biomass and growth rate of annual pasture in the winter rainfall regions of southern Australia using satellite images (Edirisinghe et al., 2002). Producer groups were set up to pilot test the delivery of satellitederived pasture growth rate (PGR, kg dry matter/hectare.day) and biomass (feed on offer or FOO, kg dry matter/hectare) predictions for paddocks on individual farms in Western Australia. This paper reports on the value to Australian sheep producers of satellite-derived PGR information on pastures
Red nuggets grow inside-out: evidence from gravitational lensing
We present a new sample of strong gravitational lens systems where both the
foreground lenses and background sources are early-type galaxies. Using imaging
from HST/ACS and Keck/NIRC2, we model the surface brightness distributions and
show that the sources form a distinct population of massive, compact galaxies
at redshifts , lying systematically below the
size-mass relation of the global elliptical galaxy population at those
redshifts. These may therefore represent relics of high-redshift red nuggets or
their partly-evolved descendants. We exploit the magnifying effect of lensing
to investigate the structural properties, stellar masses and stellar
populations of these objects with a view to understanding their evolution. We
model these objects parametrically and find that they generally require two
S\'ersic components to properly describe their light profiles, with one more
spheroidal component alongside a more envelope-like component, which is
slightly more extended though still compact. This is consistent with the
hypothesis of the inside-out growth of these objects via minor mergers. We also
find that the sources can be characterised by red-to-blue colour gradients as a
function of radius which are stronger at low redshift -- indicative of ongoing
accretion -- but that their environments generally appear consistent with that
of the general elliptical galaxy population, contrary to recent suggestions
that these objects are predominantly associated with clusters.Comment: 21 pages; accepted for publication in MNRA
Flora of the Erie Islands: A Review of Floristic, Ecological and Historical Research and Conservation Activities, 1976 – 2010
Author Institution: Lake Erie Islands Chapter, Black Swamp Conservancy, Put-in-Bay, OHAuthor Institution: Biota of North American Program, Chapel Hill, NCAuthor Institution: Ontario Natural Heritage Information Centre, Ministry of Natural Resources, Ontario, CanadaThe purpose of this review is to survey the floristic, ecological and historical research about the Erie Islands and its flora since 1976 and to describe efforts to conserve Erie Island habitats. Island location records, surveys and multi-island inventories reveal that over 1,000 vascular plant taxa are known from the Erie Islands and new records continue to be found. Alvar habitats, rare globally, occur on the Erie Islands and are a focus of conservation efforts. Forest composition is primarily related to island elevation above lake level and moisture availability. Patterns of succession in abandoned vineyards and orchards are not the same due to differing agricultural practices prior to abandonment that favored different suites of invading species. Applying island
biogeographic theory and methods to analyze the flora of the Erie Islands demonstrated that the indigenous flora on individual islands varies in relation to the size of an island in accordance with biogeographic theory whereas the non-indigenous flora on smaller islands is a constantly changing random subset of the non-indigenous flora of larger islands. Geological and palynological research about pre-settlement forests support the historic descriptions of these forests by early European settlers. Governmental
and private efforts to preserve Erie Island habitats and the flora therein expanded significantly in the past 35 years. Efforts by the State of Ohio, the Province of Ontario, non-governmental organizations and island communities to acquire and conserve unique island habitats resulted in the preservation of important alvar, wetland and woodland habitat on large islands and the acquisition
of Green Island, Middle Island and West Sister Island
Levi-Civita cylinders with fractional angular deficit
The angular deficit factor in the Levi-Civita vacuum metric has been
parametrized using a Riemann-Liouville fractional integral. This introduces a
new parameter into the general relativistic cylinder description, the
fractional index {\alpha}. When the fractional index is continued into the
negative {\alpha} region, new behavior is found in the Gott-Hiscock cylinder
and in an Israel shell.Comment: 5 figure
Fractional derivatives of random walks: Time series with long-time memory
We review statistical properties of models generated by the application of a
(positive and negative order) fractional derivative operator to a standard
random walk and show that the resulting stochastic walks display
slowly-decaying autocorrelation functions. The relation between these
correlated walks and the well-known fractionally integrated autoregressive
(FIGARCH) models, commonly used in econometric studies, is discussed. The
application of correlated random walks to simulate empirical financial times
series is considered and compared with the predictions from FIGARCH and the
simpler FIARCH processes. A comparison with empirical data is performed.Comment: 10 pages, 14 figure
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