141 research outputs found
Age and Metallicity Distribution of the Galactic Bulge from Extensive Optical and Near-IR Stellar Photometry
We present a new determination of the metallicity distribution, age, and
luminosity function of the Galactic bulge stellar population. By combining
near-IR data from the 2MASS survey, from the SOFI imager at ESO NTT and the
NICMOS camera on board HST we were able to construct color-magnitude diagrams
(CMD) and luminosity functions (LF) with large statistics and small photometric
errors from the Asymptotic Giant Branch (AGB) and Red Giant Branch (RGB) tip
down to . This is the most extended and complete LF so far
obtained for the galactic bulge. Similar near-IR data for a disk control field
were used to decontaminate the bulge CMDs from foreground disk stars, and hence
to set stronger constraint on the bulge age, which we found to be as large as
that of Galactic globular clusters, or \gsim 10 Gyr. No trace is found for
any younger stellar population. Synthetic CMDs have been constructed to
simulate the effect of photometric errors, blending, differential reddening,
metallicity dispersion and depth effect in the comparison with the
observational data. By combining the near-IR data with optical ones, from the
Wide Field Imager at the ESO/MPG 2.2m telescope, a disk-decontaminated
CMD has been constructed and used to derive the bulge metallicity
distribution, by comparison with empirical RGB templates. The bulge metallicity
is found to peak at near solar value, with a sharp cutoff just above solar, and
a tail towards lower metallicity that does not appreciably extend below
[M/H].Comment: 28 pages, 27 figures, A&A in press Full resolution version available
at http://www.eso.org/~mzoccali/bulgepap
V, J, H and K Imaging of the Metal Rich Globular Cluster NGC 6528
New near-infrared observations of NGC6528 are presented. The JHK observations
complement a previous HST/NICMOS data set by Ortolani et al. (2001), in that
they sample a larger area, contain a more numerous sample of red giant stars,
and include the K band. Also, archival HST data sets (separated by 6.093 years)
were used to proper-motion decontaminate the near-infrared sample and extract a
clean VJHK catalogue. Using the present wide colour baseline, we compared the
cleaned colour-magnitude diagrams of NGC6528 with those of NGC 6553 and NGC104
and derived new estimates of reddening and distance, E(B-V)=0.55 and
(m-M)o=14.44 (7.7 kpc). Moreover, the morphology and location of the cleaned
red giant branch were used to derive a photometric estimate of the cluster
metallicity. The average of 10 metallicity indicators yields a mean value of
[M/H] ~ 0.0, and [Fe/H] ~-0.20 and +0.08 on the Zinn & West (1984) and Carretta
& Gratton (1997) revised metallicity scale, respectively. The best isochrone
fit to the cleaned K,V-K diagram is obtained for a 12.6 Gyr and Z=0.02
isochrone, i.e. the derived metallicity of NGC6528 turns out to be very close
to the mean of stars in the Baade's Window. Five AGB variable star candidates,
whose membership has to be confirmed spectroscopically, are bolometrically as
bright as the known long period variable stars in NGC6553. As discussed in
Guarnieri et al. (1997) for NGC6553, this may indicate that an `intermediate
age' population is not needed to account for the brightest stars in external
galaxies such as M32.Comment: 11 pages, 9 figures, A&A accepte
VLT-UVES abundance analysis of four giants in NGC 6553
Metal-rich globular clusters trace the formation of bulges. Abundance ratios
in the metal-rich globular clusters such as NGC 6553 can constrain the
formation timescale of the Galactic bulge. The purpose of this study is
determine the metallicity and elemental ratios in individual stars of the
metal-rich bulge globular cluster NGC 6553. A detailed abundance analysis of
four giants in NGC 6553 is carried out, based on optical high-resolution
echelle spectra obtained with UVES at the ESO VLT-UT2 Kueyen telescope. A
metallicity [Fe/H]= -0.20 dex is derived, together with -element
enhancement of Mg and Si ([Mg/Fe]=+0.28, [Si/Fe]=+0.21), solar Ca and Ti
([Ca/Fe]=+0.05, [Ti/Fe]=-0.01), and a mild enhancement of the r-process element
Eu with [Eu/Fe] = +0.10. A mean heliocentric radial velocity of -1.86 km
s is measured. We compare our results with previous investigations of
the cluster.Comment: 15 pages, 8 figures, A&A, in pres
The Spectral Energy Distributions of White Dwarfs in 47 Tucanae: The Distance to the Cluster
We present a new distance determination to the Galactic globular cluster 47
Tucanae by fitting the spectral energy distributions of its white dwarfs to
pure hydrogen atmosphere white dwarf models. Our photometric dataset is
obtained from a 121 orbit Hubble Space Telescope program using the Wide Field
Camera 3 UVIS/IR channels, capturing F390W, F606W, F110W, and F160W images.
These images cover more than 60 square arcmins and extend over a radial range
of 5-13.7 arcmin (6.5-17.9 pc) within the globular cluster. Using a likelihood
analysis, we obtain a best fitting unreddened distance modulus of (m -
M)o=13.36+/-0.02+/-0.06 corresponding to a distance of 4.70+/-0.04+/-0.13 kpc,
where the first error is random and the second is systematic. We also search
the white dwarf photometry for infrared excess in the F160W filter, indicative
of debris disks or low mass companions, and find no convincing cases within our
sample.Comment: Accepted to The Astronomical Journal, 13 Figures, 2 Tables. Figures 3
and 6 are figure sets, each composed of 59 subfigures (to appear in the
electronic journal). This is a Companion paper to the article ID:
submit/037561
The propagation of uncertainties in stellar population synthesis modeling III: model calibration, comparison, and evaluation
Stellar population synthesis (SPS) provides the link between the stellar and
dust content of galaxies and their observed spectral energy distributions. In
the present work we perform a comprehensive calibration of our own flexible SPS
(FSPS) model against a suite of data. Several public SPS models are
intercompared, including the models of Bruzual & Charlot (BC03), Maraston (M05)
and FSPS. The relative strengths and weaknesses of these models are evaluated,
with the following conclusions: 1) The FSPS and BC03 models compare favorably
with MC data at all ages, whereas M05 colors are too red and the age-dependence
is incorrect; 2) All models yield similar optical and near-IR colors for old
metal-poor systems, and yet they all provide poor fits to the integrated J-K
and V-K colors of both MW and M31 star clusters; 4) All models predict ugr
colors too red, D4000 strengths too strong and Hdelta strengths too weak
compared to massive red sequence galaxies, under the assumption that such
galaxies are composed solely of old metal-rich stars; 5) FSPS and, to a lesser
extent, BC03 can reproduce the optical and near-IR colors of post-starburst
galaxies, while M05 cannot. Reasons for these discrepancies are explored. The
failure at predicting the ugr colors, D4000, and Hdelta strengths can be
explained by some combination of a minority population of metal-poor stars,
young stars, blue straggler and/or blue horizontal branch stars, but not by
appealing to inadequacies in either theoretical stellar atmospheres or
canonical evolutionary phases (e.g., the main sequence turn-off). We emphasize
that due to a lack of calibrating star cluster data in regions of the
metallicity-age plane relevant for galaxies, all of these models continue to
suffer from serious uncertainties that are difficult to quantify. (ABRIDGED)Comment: 26 pages, 16 figures, submitted to ApJ. The FSPS code can be
downloaded at http://www.astro.princeton.edu/~cconroy/SPS
Theropod Fauna from Southern Australia Indicates High Polar Diversity and Climate-Driven Dinosaur Provinciality
The Early Cretaceous fauna of Victoria, Australia, provides unique data on the composition of high latitude southern hemisphere dinosaurs. We describe and review theropod dinosaur postcranial remains from the Aptian–Albian Otway and Strzelecki groups, based on at least 37 isolated bones, and more than 90 teeth from the Flat Rocks locality. Several specimens of medium- and large-bodied individuals (estimated up to ∼8.5 metres long) represent allosauroids. Tyrannosauroids are represented by elements indicating medium body sizes (∼3 metres long), likely including the holotype femur of Timimus hermani, and a single cervical vertebra represents a juvenile spinosaurid. Single specimens representing medium- and small-bodied theropods may be referrable to Ceratosauria, Ornithomimosauria, a basal coelurosaur, and at least three taxa within Maniraptora. Thus, nine theropod taxa may have been present. Alternatively, four distinct dorsal vertebrae indicate a minimum of four taxa. However, because most taxa are known from single bones, it is likely that small-bodied theropod diversity remains underestimated. The high abundance of allosauroids and basal coelurosaurs (including tyrannosauroids and possibly ornithomimosaurs), and the relative rarity of ceratosaurs, is strikingly dissimilar to penecontemporaneous dinosaur faunas of Africa and South America, which represent an arid, lower-latitude biome. Similarities between dinosaur faunas of Victoria and the northern continents concern the proportional representatation of higher clades, and may result from the prevailing temperate–polar climate of Australia, especially at high latitudes in Victoria, which is similar to the predominant warm–temperate climate of Laurasia, but distinct from the arid climate zone that covered extensive areas of Gondwana. Most dinosaur groups probably attained a near-cosmopolitan distribution in the Jurassic, prior to fragmentation of the Pangaean supercontinent, and some aspects of the hallmark ‘Gondwanan’ fauna of South America and Africa may therefore reflect climate-driven provinciality, not vicariant evolution driven by continental fragmentation. However, vicariance may still be detected at lower phylogenetic levels
VLT-FLAMES Analysis of 8 giants in the Bulge Metal-poor Globular Cluster NGC 6522: Oldest Cluster in the Galaxy?
NGC 6522 has been the first metal-poor globular cluster identified in the
bulge by W. Baade. Despite its importance, very few high resolution abundance
analyses of stars in this cluster are available in the literature. The bulge
metal-poor clusters may be important tracers of the early chemical enrichment
of the Galaxy. The main purpose of this study is the determination of
metallicity and elemental ratios in individual stars of NGC 6522. High
resolution spectra of 8 giants of the bulge globular cluster NGC 6522 were
obtained at the 8m VLT UT2-Kueyen telescope with the FLAMES+GIRAFFE
spectrograph. Multiband V,I,J,Ks} photometry was used to derive effective
temperatures as reference values. Spectroscopic parameters are derived from FeI
and FeII lines, and adopted for the derivation of abundance ratios. The present
analysis provides a metallicity [Fe/H] = -1.0+-0.2. The alpha-elements Oxygen,
Magnesium and Silicon show [O/Fe]=+0.4, [Mg/Fe]=[Si/Fe]= +0.25, whereas Calcium
and Titanium show shallower ratios of [Ca/Fe]=[Ti/Fe]=+0.15. The
neutron-capture r-process element Europium appears to be overabundant by
[Eu/Fe]=+0.4. The neutron-capture s-elements La and Ba are enhanced by
[La/Fe]=+0.35 and [Ba/Fe]=+0.5. The large internal errors, indicating the large
star-to-star variationin the Ba and Eu abundances, are also discussed. The
moderate metallicity combined to a blue Horizontal Branch (BHB), are
characteristics similar to those of HP~1 and NGC 6558, pointing to a population
of very old globular clusters in the Galactic bulge. Also, the abundance ratios
in NGC 6522 resemble those in HP 1 and NGC 6558. The ultimate conclusion is
that the bulge is old, and went through an early prompt chemical enrichment.Comment: 18 pages, 16 figures. Astronomy & Astrophysics, accepte
Governing through choice: Food labels and the confluence of food industry and public health discourse to create ‘healthy consumers’
Food industry and public health representatives are often in conflict, particularly over food labelling policies and regulation. Food corporations are suspicious of regulated labels and perceive them as a threat to free market enterprise, opting instead for voluntary labels. Public health and consumer groups, in contrast, argue that regulated and easy-to-read labels are essential for consumers to exercise autonomy and make healthy choices in the face of food industry marketing. Although public health and food industry have distinct interests and objectives, I argue that both contribute to the creation of the food label as a governmental strategy that depends on free-market logics to secure individual and population health. While criticism of ‘Big Food’ has become a growth industry in academic publishing and research, wider critique is needed that also includes the activities of public health. Such a critique needs to address the normalizing effect of neoliberal governmentality within which both the food industry and public health operate to reinforce individuals as ‘healthy consumers’. Drawing on Michel Foucault’s lectures at the Collège de France, I examine the food label through the lens of governmentality. I argue that the rationale operating through the food label combines nutrition science and free-market logics to normalize subjects as responsible for their own health and reinforces the idea of consumption as a means to secure population health from diet-related chronic diseases
Shared heritability of attention-deficit/hyperactivity disorder and autism spectrum disorder
Attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) are both highly heritable neurodevelopmental disorders. Evidence indicates both disorders co-occur with a high frequency, in 20–50% of children with ADHD meeting criteria for ASD and in 30-80% of ASD children meeting criteria for ADHD. This review will provide an overview on all available studies [family based, twin, candidate gene, linkage, and genome wide association (GWA) studies] shedding light on the role of shared genetic underpinnings of ADHD and ASD. It is concluded that family and twin studies do provide support for the hypothesis that ADHD and ASD originate from partly similar familial/genetic factors. Only a few candidate gene studies, linkage studies and GWA studies have specifically addressed this co-occurrence, pinpointing to some promising pleiotropic genes, loci and single nucleotide polymorphisms (SNPs), but the research field is in urgent need for better designed and powered studies to tackle this complex issue. We propose that future studies examining shared familial etiological factors for ADHD and ASD use a family-based design in which the same phenotypic (ADHD and ASD), candidate endophenotypic, and environmental measurements are obtained from all family members. Multivariate multi-level models are probably best suited for the statistical analysis
Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world
Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic.
Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality.
Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States.
Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis.
Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection
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