The ages of the oldest and most metal-poor stars in the Milky Way bear important information on the age of the universe and its standard model. We analyze a sample of 28 extremely metal-poor field stars in the solar vicinity culled from the literature and carefully determine their ages. To this aim, we critically make use of Gaia data to derive their distances and associated uncertainties. Particular attention has been paid to the estimate of the reddening and its effect on the derivation of stellar ages. We employed different reddenings and superimpose isochrones from different sources on the stars' color–magnitude diagram built up with different photometric systems. We highlight subtle metallicity effects when using the Johnson photometry for low-metallicity stars and finally adopt Gaia photometry. An automatic fitting method is devised to assign ages to each individual star taking into account the uncertainties in the input parameters. The mean age of the sample turns out to be 13.9 ± 0.5 Gyr using Padova isochrones, and 13.7 ± 0.4 Gyr using BASTI isochrones. We found also a group of very metal-poor stars ([Fe/H] = −2.7 to −2.0 dex) with relatively young ages, in the range 8–10 Gyr.
Very metal-poor stars contain crucial information on the Milky Way’s infancy. In our previous study we derived a mean age of ∼13.7 Gyr for a sample of these stars in the Sun’s vicinity. In this work, we investigate the chemical and kinematic properties of these stars with the goal of obtaining some insights into their origin and their parent population. We did not find any Al–Mg anticorrelation, which leads us to the conclusion that these stars did not form in globular clusters, while the detailed analysis of their orbital parameters reveals that these stars are most probably associated with the pristine bulge of the Milky Way. We then sketch a scenario for the formation of the Milky Way in which the first structure to form was the bulge through rapid collapse. The other components have grown later on, with a significant contribution of accreted structures.
Relevance of the study. The problem of thematic misbalance in news is indisputable nowadays. Newsmakers are obliged to meet not only standard news criteria, but also a media audience expectations regarding the structuring of its interests. The main objectives of the study were to detect the coherence in agendas of the leading Ukrainian TV channels as well as to trace their conformity with the public agenda. Methodology. Content-analysis method was used to identify those topics in news stories (N=1186) that got the most attention on the studied channels. Calculating the coherence and rank correlation coefficients made it possible to trace the commonality in thematic priorities among channels themselves and between channels and their audience. Data triangulation method made it possible to select the points of public agenda from the survey by the -Democratic Initiatives‖ Foundation. Results. The studied channels tend to reflect Ukrainian and world events in identical thematic proportions: coherence coefficient of devotion attention to the topics was fixed at a high level: W = 0.87 (p≤0.005). There is a tendency for emphasizing particular range of issues (bureaucrats, corruption, crime, material support) and missing from attention of some others (decentralization, environmental issues). Only a half of the topics (49%) was identified as important to the public's view, other issues didn't correspond to public agenda, therefore, the manifestation of the agendasetting effect was fixed at a weak level (r = 0.2 at p> 0.1). The probable cause of the low correlation between media and public agendas may be the deterioration of living standards in Ukraine due to current state of war conflict. Conclusions. In terms of thematic priorities, leading television channels can be characterized by a high degree of consistency, while the television agenda is only half-compliant with public agenda, so that its conformity with the public agenda was fixed at a weak level.
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