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The late Paleozoic Ice Age along the southwestern margin of Gondwana: Facies models, age constraints, correlation and sequence stratigraphic framework
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Differential reddening corrected HST ACS photometry, Monte Carlo Parameters and Monte Carlo isochrones used to estimate the absolute age of NGC3201. The columns in the NGC3201_fitstars_DRCR.dat file are:x = star x position on the master framey = star y position on the master framev = F606W VEGA magi = F814W VEGA magvi = V-I VEGAmag Detailed instruction to read MC parameters and MC isochrones can be found in the notebook: Instruction on reading NGC3201 isochrones.ipynbmore » « less
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Abstract The absolute age of a simple stellar population is of fundamental interest for a wide range of applications but is difficult to measure in practice, as it requires an understanding of the uncertainties in a variety of stellar evolution processes as well as the uncertainty in the distance, reddening, and composition. As a result, most studies focus only on the relative age by assuming that stellar evolution calculations are accurate and using age determinations techniques that are relatively independent of distance and reddening. Here, we construct 20,000 sets of theoretical isochrones through Monte Carlo simulation using the Dartmouth Stellar Evolution Program to measure the absolute age of the globular cluster M92. For each model, we vary a range of input physics used in the stellar evolution models, including opacities, nuclear reaction rates, diffusion coefficients, atmospheric boundary conditions, helium abundance, and treatment of convection. We also explore variations in the distance and reddening as well as its overall metallicity andαenhancement. We generate simulated Hess diagrams around the main-sequence turn-off region from each set of isochrones and use a Voronoi binning method to fit the diagrams to Hubble Space Telescope Advanced Camera for Surveys data. We find the age of M92 to be 13.80 ± 0.75 Gyr. The 5.4% error in the absolute age is dominated by the uncertainty in the distance to M92 (∼80% of the error budget); of the remaining parameters, only the total metallicity,αelement abundance, and treatment of helium diffusion contribute significantly to the total error.more » « less
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Abstract This study addresses the development of an absolute chronology for prominent burial sites of Inner Asian nomadic cultures. We investigate Saka archaeological wood from a well-known gold-filled Baigetobe kurgan (burial mound #1 of Shilikty-3 cemetery) to estimate its calendar age using tree-ring and 14 C dating. The Saka was the southernmost tribal group of Asian Scythians, who roamed Central Asia during the 1st millennium BC (Iron Age). The Shilikty is a large burial site located in the Altai Mountains along the border between Kazakhstan and China. We present a new floating tree-ring chronology of larch and five new 14 C dates from the construction timbers of the Baigetobe kurgan. The results of Bayesian modeling suggest the age of studied timbers is ~730–690 cal BC. This places the kurgan in early Scythian time and authenticates a previously suggested age of the Baigetobe gold collection between the 8th and 7th centuries BC derived from the typology of grave goods and burial rites. Chronologically and stylistically, the Scythian Animal Style gold from the Baigetobe kurgan is closer to Early Scythians in the North Caucasus and Tuva than to the local Saka occurrences in the Kazakh Altai. Our dating results indicate that the Baigetobe kurgan was nearly contemporaneous to the Arjan-2 kurgan (Tuva) and could be one of the earliest kurgans of the Saka-Scythian elite in Central Asia.more » « less
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A source node updates its status as a point process and also forwards its updates to a network of observer nodes. Within the network of observers, these updates are forwarded as point processes from node to node. Each node wishes its knowledge of the source to be as timely as possible. In this network, timeliness is measured by a discrete form of age of information: each status change at the source is referred to as a version and the age at a node is how many versions out of date is its most recent update from the source. This work introduces a method for evaluating the average version age at each node in the network when nodes forward updates using a memoryless gossip protocol. This method is then demonstrated by version age analysis for a collection of simple networks. For gossip on a complete graph with symmetric updating rates, it is shown that each node has average age that grows as the logarithm of the network size.more » « less
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.jsames.2020.103056
