{"paper":{"title":"Mapping systematic errors in helium abundance determinations using Markov Chain Monte Carlo","arxiv_id":"1012.2385","primary_cat":"astro-ph.CO","submitted_at":"2010-12-10T21:01:58+00:00","version_compiled":"v1"},"notice":"Every quoted sentence is the authors' text from the arXiv listing abstract. Labels and probabilities are the outputs of classifier-1.13-20260917 on the question bank abstract-p1-20260923, exactly as returned. 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region.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.07,"main_claim_p":0.02,"quantitative":false,"quantitative_p":0.03,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.0,"background":1.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.0}},{"i":2,"p":0.88,"id":"s2","own":true,"role":"contribution","text":"In this work, we introduce Markov Chain Monte Carlo (MCMC) methods to efficiently explore the parameter space and determine the helium abundance, the physical parameters, and the uncertainties derived from observations of metal poor nebulae.","hedge":{"p":0.99,"label":"asserted"},"own_p":0.93,"main_claim_p":0.08,"quantitative":false,"quantitative_p":0.04,"role_probabilities":{"gap":0.0,"method":0.12,"result":0.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.88,"interpretation":0.0}},{"i":3,"p":0.9,"id":"s3","own":true,"role":"result","text":"Experiments with synthetic data show that the MCMC method is superior to previous implementations (based on flux perturbation) in that it is not affected by biases due to non-physical parameter space.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.86,"main_claim_p":0.17,"quantitative":true,"quantitative_p":0.74,"role_probabilities":{"gap":0.0,"method":0.02,"result":0.9,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.07,"interpretation":0.01}},{"i":4,"p":0.65,"id":"s4","own":true,"role":"result","text":"The MCMC analysis allows a detailed exploration of degeneracies, and, in particular, a false minimum that occurs at large values of optical depth in the He~I emission lines.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.86,"main_claim_p":0.09,"quantitative":false,"quantitative_p":0.07,"role_probabilities":{"gap":0.0,"method":0.1,"result":0.65,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.23,"interpretation":0.02}},{"i":5,"p":0.49,"id":"s5","own":true,"role":"result","text":"We demonstrate that introducing the electron temperature derived from the [O~III] emission lines as a prior, in a very conservative manner, produces negligible bias and effectively eliminates the false minima occurring at large optical depth.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.95,"main_claim_p":0.18,"quantitative":false,"quantitative_p":0.25,"role_probabilities":{"gap":0.0,"method":0.35,"result":0.49,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.15,"interpretation":0.01}},{"i":6,"p":0.88,"id":"s6","own":true,"role":"method","text":"We perform a frequentist analysis on data from several \"high quality\" systems.","hedge":{"p":0.98,"label":"asserted"},"own_p":0.95,"main_claim_p":0.03,"quantitative":false,"quantitative_p":0.06,"role_probabilities":{"gap":0.0,"method":0.88,"result":0.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.12,"interpretation":0.0}},{"i":7,"p":0.44,"id":"s7","own":true,"role":"method","text":"Likelihood plots illustrate degeneracies, asymmetries, and limits of the determination.","hedge":{"p":0.99,"label":"asserted"},"own_p":0.85,"main_claim_p":0.04,"quantitative":false,"quantitative_p":0.06,"role_probabilities":{"gap":0.0,"method":0.44,"result":0.29,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.24,"interpretation":0.03}},{"i":8,"p":0.76,"id":"s8","own":true,"role":"result","text":"In agreement with previous work, we find relatively large systematic errors, limiting the precision of the primordial helium abundance for currently available spectra.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.89,"main_claim_p":0.67,"quantitative":false,"quantitative_p":0.33,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.76,"background":0.0,"limitation":0.07,"future_work":0.0,"contribution":0.0,"interpretation":0.17}}]},"compiled":{"main_claim":{"p":0.98,"text":"In agreement with previous work, we find relatively large systematic errors, limiting the precision of the primordial helium abundance for currently 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