We present a new geometric distortion model for the narrow-field mode of the near-infrared camera (NIRC2) fed by the adaptive optics system on the W. M. Keck II telescope. The adaptive optics system ...and NIRC2 camera were realigned on 2015 April 13. Observations of the crowded globular cluster, M53, were obtained before and after the realignment to characterize the geometric field distortion. The distorted NIRC2 positions of M53 stars were compared with precise astrometry of this cluster from Hubble Space Telescope observations. The resulting distortion map constructed just before the realignment is consistent with the previous solution derived using data from 2007 to 2009, indicating that the distortion has been stable to ∼0.5 mas. The distortion map changed significantly after a realignment of 4.5 mas (75%) rms, and the new distortion model for post-realignment observations have a total accuracy of ∼1.1 mas.
We present improved relative astrometry for stars within the central half parsec of our Galactic Center (GC) based on data obtained with the 10 m W. M. Keck Observatory from 1995 to 2017. The new ...methods used to improve the astrometric precision and accuracy include correcting for local astrometric distortions, applying a magnitude-dependent additive error, and more carefully removing instances of stellar confusion. Additionally, we adopt jackknife methods to calculate velocity and acceleration uncertainties. The resulting median proper motion uncertainty is 0.05 mas yr−1 for our complete sample of 1184 stars in the central 10″ (0.4 pc). We have detected 24 accelerating sources, 2.6 times more than the number of previously published accelerating sources, which extend out to 4″ (0.16 pc) from the black hole. Based on S0-2's orbit, our new astrometric analysis has reduced the systematic error of the supermassive black hole (SMBH) by a factor of 2. The linear drift in our astrometric reference frame is also reduced in the north-south direction by a factor of 4. We also find the first potential astrometric binary candidate S0-27 in the GC. These astrometric improvements provide a foundation for future studies of the origin and dynamics of the young stars around the SMBH, the structure and dynamics of the old nuclear star cluster, the SMBH's properties derived from orbits, and tests of general relativity in a strong gravitational field.
ʻImaka is a ground-layer adaptive optics (GLAO) demonstrator on the University of Hawaii 2.2 m telescope with a 24′ × 18′ field of view, nearly an order of magnitude larger than previous AO ...instruments. In 15 nights of observing with natural guide star asterisms ∼16′ in diameter, we measure median AO-off and AO-on empirical FWHMs of 0 95 and 0 64 in R band, 0 81 and 0 48 in I band, and 0 76 and 0 44 at 1 m. This factor of 1.5-1.7 reduction in the size of the point-spread function (PSF) results from correcting both the atmosphere and telescope tracking errors. The AO-on PSF is uniform out to field positions ∼5′ off-axis, with a typical standard deviation in the FWHM of 0 018. Images exhibit variation in FWMM by 4.5% across the field, which has been applied as a correction to the aforementioned quantities. The AO-on PSF is also 10× more stable in time compared to the AO-off PSF. In comparing the delivered image quality to proxy measurements, we find that in both AO-off and AO-on data delivered image quality is correlated with ʻImaka's telemetry, with R-band correlation coefficients of 0.68 and 0.70, respectively. At the same wavelength, the data are correlated to DIMM and MASS seeing with coefficients of 0.45 and 0.55, respectively. Our results are an essential first step to implementing facility-class, wide-field GLAO on Maunakea telescopes, enabling new opportunities to study extended astronomical sources, such as deep galaxy fields, nearby galaxies, or star clusters, at high angular resolution.
This paper describes the development and application of an integrated framework for determination of sustainable carrying capacity in shellfish growing areas. This framework combines field data, ...experimental results and various types of models, ranging from individual shellfish growth models to broad-scale ecosystem models. The process by which we have integrated and coupled the various types of models is designed to capture the essential signal at each simulation scale, whilst allowing multi-year runs which provide results on cultivation of commercial species, nutrient and chlorophyll cycling, and other outputs of interest to decision-makers. The complete modelling framework enables integrated analyses of animal–environment interrelations affecting overall production at system-scales, according to different temporal and spatial scenarios, accounting for conservation aspects such as the presence of autochthonous wild species.
This framework was applied to three loughs in Northern Ireland; Carlingford (a transboundary system), Strangford and Belfast, to provide estimates of harvestable biomass over typical cultivation cycles of 2–3 years in both the blue mussel Mytilus edulis and the Pacific oyster Crassostrea gigas. The model accommodates different types of culture, whether subtidally on the bottom, suspended from rafts or intertidally on trestles.
Results predicted for Carlingford and Strangford are within ranges of landings reported by fisheries agencies. In Belfast lough, where 10,000 ton live weight are reported annually, our model framework provides stable results of 8700 ton after a 10 year model run. These models are shown to be useful for driving farm-scale simulations, which are of great interest to producers, and also for analyses of the consequences of changed environmental conditions or in the timing, distribution and/or composition of culture practice. Examples are presented that include (i) an analysis of the spatial redistribution of mussel culture, illustrating changes both to production and to the Average Physical Product; (ii) assessment of the differential effects of climate change on mussel and oyster production, indicating that oysters are significantly less impacted; and (iii) investigation of the consequences of including wild suspension-feeding species in the model framework, resulting in an expected reduction in the capacity for production of cultivated shellfish. These scenarios were produced to illustrate the uses of the modelling approach, and enable better-informed discussion between different stakeholders, towards sustainable aquaculture (ecoaquaculture).
Filter feeding was compared in the blue mussel Mytilus edulis, Mediterranean mussel Mytilus galloprovincialis, Pacific oyster Crassostrea gigas, Chinese pleated oyster Crassostrea plicatula, Chinese ...scallop Chlamys farreri,Manila clam Tapes phillipinarum, razor clam Sinonvacula constricta, and blood cockle Tegillarca granosa over 95 dietary conditions across nine locations in Europe and China. Conditions included natural seawater enhanced, on occasion, with variable additions of microalgal monoculture and/or natural silt collected from the surface of nearby mudflats, thereby ensuring that diets ranged from oligotrophic to hypereutrophic (>325 µg chlorophyll a/L) and highly turbid (>1,250 mg total particulate matter/L). Building on past insights into differential particle processing, we resolved the availability, filtration, and ingestion of organic matter rich in chlorophyll a, and which matter is known to be ingested selectively, from all remaining organics, such as detritus, bacteria, protozoans, and/or colloids. The forms of fitted relations that best described feeding responses were different for chlorophyll-rich versus remaining organics, that difference being consistent in all eight bivalve species, including when measured in the same species across different locations. Throughout, positive linear relations between net ingestion of chlorophyll-rich organic matter and the availability of that chlorophyll-rich organic matter indicated that each species ingested constant proportions of the organics associated with chlorophyll a, with no limitation evident to such ingestion over our experimental range. Alternatively, ingestion of the remaining organics by each species increased as saturating functions of the availability of those remaining organics alone. Differences were evident between species both in the proportions of available chlorophyll-rich organic matter that were ingested and in saturated ingestion rates for the remaining organics. Comparison of those differences suggests an evolutionary trade-off among species between their relative abilities to process chlorophyll-rich versus remaining organics. Differences also suggest congeneric adaptation to natural habitat, impressing a need for careful appraisal of each and every bivalve species. Significant costs of particle sorting, digestion, and absorption, evidenced as metabolically derived material egested and assayed within feces, were greatest in species with higher saturated capacities for the ingestion of remaining organics. Last, we describe how, compared with predictions based on chlorophyll a or total particulate organic matter alone, our approach resolving coincident differential availabilities and processing of chlorophyll-rich versus remaining organic matter has improved the accuracy of growth simulations when applying single calibrations of the generic shellfish model ShellSIM across coastal habitats that contrast in seston composition.
A review is presented of all aspects of adult mosquito dispersal, encompassing transportation of mosquitoes by ships, airplanes and trains, long distance wind-assisted dispersal, and much shorter ...almost daily flights that mosquitoes make to locate mates, blood sources, nectar, oviposition sites, and resting sites. The many definitions and concepts of animal migration are debated, and instances of so-called mosquito migration, that is long distance wind-assisted flights, and the ecological advantages and disadvantages of such journeys are examined. It is concluded that there is little evidence that mosquitoes make purposeful long distance flights that can be classified zoologically as migration. It is argued that it is better to regard all mosquito flights as dispersal. Host orientation cues are not discussed, but the contentious idea of a memorized home range between feeding and oviposition sites is presented
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