Zirconium, Barium, Lanthanum and Europium Abundances in Open Clusters

We present an analysis of the s-process elements Zr, Ba, and La and the r-process element Eu in a sample of 50 stars in 19 open clusters. Stellar abundances of each element are based on measures of a minimum of two lines per species via both equivalent width and spectrum synthesis techniques. We investigate cluster mean neutron-capture abundance trends as a function of cluster age and location in the Milky Way disk and compare them to results found in other studies in the literature. We find a statistically significant trend of increasing cluster [Ba/Fe] as a function of decreasing cluster age, in agreement with recent findings for other open cluster samples, supporting the increased importance of low-mass asymptotic giant branch stars to the generation of s-process elements. However, the other s-process elements, [La/Fe] and [Zr/Fe], do not show similar dependences, in contrast to theoretical expectations and the limited observational data from other studies. Conversely, cluster [Eu/Fe] ratios show a slight increase with increasing cluster age, although with marginal statistical significance. Ratios of [s/r]-process abundances, [Ba/Eu] and [La/Eu], however, show more clearly the increasing efficiency of s-process relative to r-process enrichment in open cluster chemical evolution, with significant increases among younger clusters. Last, cluster neutron-capture element abundances appear to be independent of Galactocentric distance. We conclude that a homogeneous analysis of a larger sample of open clusters is needed to resolve the apparent discrepant conclusions between different studies regarding s-process element abundance trends with age to better inform models of galactic chemical evolution.Comment: 24 pages, 13 figures, 10 tables; published in The Astronomical Journa

Climate change and health in Earth's future

Threats to health from climate change are increasingly recognized, yet little research into the effects upon health systems is published. However, additional demands on health systems are increasingly documented. Pathways include direct weather impacts, such as amplified heat stress, and altered ecological relationships, including alterations to the distribution and activity of pathogens and vectors. The greatest driver of demand on future health systems from climate change may be the alterations to socioeconomic systems; however, these “tertiary effects” have received less attention in the health literature. Increasing demands on health systems from climate change will impede health system capacity. Changing weather patterns and sea-level rise will reduce food production in many developing countries, thus fostering undernutrition and concomitant disease susceptibility. Associated poverty will impede people’s ability to access and support health systems. Climate change will increase migration, potentially exposing migrants to endemic diseases for which they have limited resistance, transporting diseases and fostering conditions conducive to disease transmission. Specific predictions of timing and locations of migration remain elusive, hampering planning and misaligning needs and infrastructure. Food shortages, migration, falling economic activity, and failing government legitimacy following climate change are also “risk multipliers” for conflict. Injuries to combatants, undernutrition, and increased infectious disease will result. Modern conflict often sees health personnel and infrastructure deliberately targeted and disease surveillance and eradication programs obstructed. Climate change will substantially impede economic growth, reducing health system funding and limiting health system adaptation. Modern medical care may be snatched away from millions who recently obtained it

A Chemical Abundance Study of 10 Open Clusters Based on WIYN-Hydra Spectroscopy

We present a detailed chemical abundance study of evolved stars in 10 open clusters based on Hydra multi-object echelle spectra obtained with the WIYN 3.5m telescope. From an analysis of both equivalent widths and spectrum synthesis, abundances have been determined for the elements Fe, Na, O, Mg, Si, Ca, Ti, Ni, Zr, and for two of the 10 clusters, Al and Cr. To our knowledge, this is the first detailed abundance analysis for clusters NGC 1245, NGC 2194, NGC 2355 and NGC 2425. These 10 clusters were selected for analysis because they span a Galactocentric distance range Rgc~9-13 kpc, the approximate location of the transition between the inner and outer disk. Combined with cluster samples from our previous work and those of other studies in the literature, we explore abundance trends as a function of cluster Rgc, age, and [Fe/H]. The [Fe/H] distribution appears to decrease with increasing Rgc to a distance of ~12 kpc, and then flattens to a roughly constant value in the outer disk. Cluster average element [X/Fe] ratios appear to be independent of Rgc, although the picture for [O/Fe] is more more complicated by a clear trend of [O/Fe] with [Fe/H] and sample incompleteness. Other than oxygen, no other element [X/Fe] exhibits a clear trend with [Fe/H]; likewise, there does not appear to be any strong correlation between abundance and cluster age. We divided clusters into different age bins to explore temporal variations in the radial element distributions. The radial metallicity gradient appears to have flattened slightly as a function of time, as found by other studies. There is also indication that the transition from the inner disk to the outer disk occurs at different Galactocentric radii for different age bins. (Abridged.)Comment: 35 pages, 12 figures, 18 tables; published in The Astronomical Journal (http://stacks.iop.org/1538-3881/142/59

NGC 7789: An Open Cluster Case Study

We have obtained high-resolution spectra of 32 giants in the open cluster NGC 7789 using the Wisconsin-Indiana-Yale-NOAO Hydra spectrograph. We explore differences in atmospheric parameters and elemental abundances caused by the use of the linelist developed for the Gaia-ESO Survey (GES) compared to one based on Arcturus used in our previous work. [Fe/H] values decrease when using the GES linelist instead of the Arcturus-based linelist; these differences are probably driven by systematically lower (~ -0.1 dex) GES surface gravities. Using the GES linelist we determine abundances for 10 elements - Fe, Mg, Si, Ca, Ti, Na, Ni, Zr, Ba, and La. We find the cluster's average metallicity [Fe/H] = 0.03 +/- 0.07 dex, in good agreement with literature values, and a lower [Mg/Fe] abundance than has been reported before for this cluster (0.11 +/- 0.05 dex). We also find the neutron-capture element barium to be highly enhanced - [Ba/Fe] = +0.48 +/- 0.08 - and disparate from cluster measurements of neutron-capture elements La and Zr (-0.08 +/- 0.05 and 0.08 +/- 0.08, respectively). This is in accordance with recent discoveries of supersolar Ba enhancement in young clusters along with more modest enhancement of other neutron-capture elements formed in similar environments.Comment: 15 pages, 9 figures, Table 1 typo fixe

Elemental Abundance Ratios in Stars of the Outer Galactic Disk. IV. A New Sample of Open Clusters

We present radial velocities and chemical abundances for nine stars in the old, distant open clusters Be 18, Be 21, Be 22, Be 32, and PWM 4. For Be 18 and PWM 4, these are the first chemical abundance measurements. Combining our data with literature results produces a compilation of some 68 chemical abundance measurements in 49 unique clusters. For this combined sample, we study the chemical abundances of open clusters as a function of distance, age, and metallicity. We confirm that the metallicity gradient in the outer disk is flatter than the gradient in the vicinity of the solar neighborhood. We also confirm that the open clusters in the outer disk are metal-poor with enhancements in the ratios [alpha/Fe] and perhaps [Eu/Fe]. All elements show negligible or small trends between [X/Fe] and distance (< 0.02 dex/kpc), but for some elements, there is a hint that the local (RGC < 13 kpc) and distant (RGC > 13 kpc) samples may have different trends with distance. There is no evidence for significant abundance trends versus age (< 0.04 dex/Gyr). We measure the linear relation between [X/Fe] and metallicity, [Fe/H], and find that the scatter about the mean trend is comparable to the measurement uncertainties. Comparison with solar neighborhood field giants shows that the open clusters share similar abundance ratios [X/Fe] at a given metallicity. While the flattening of the metallicity gradient and enhanced [alpha/Fe] ratios in the outer disk suggest a different chemical enrichment history to the solar neighborhood, we echo the sentiments expressed by Friel et al. that definitive conclusions await homogeneous analyses of larger samples of stars in larger numbers of clusters. Arguably, our understanding of the evolution of the outer disk from open clusters is currently limited by systematic abundance differences between various studies.Comment: Accepted for publication in A