The distribution of [α/Fe] in the Milky Way disc

Using a sample of red giant stars from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) Data Release 16, we infer the conditional distribution p([α/Fe] | [Fe/H]) in the Milky Way disk for the α-elements Mg, O, Si, S, and Ca. In each bin of [Fe/H] and Galactocentric radius R, we model p([α/Fe]) as a sum of two Gaussians, representing ‘low-α’ and ‘high-α’ populations with scale heights z1 = 0.45 kpc and z2 = 0.95 kpc, respectively. By accounting for age-dependent and z-dependent selection effects in APOGEE, we infer the [α/Fe] distributions that would be found for a fair sample of long-lived stars covering all z. Near the Solar circle, this distribution is bimodal at sub-solar [Fe/H], with the low-α and high-α peaks clearly separated by a minimum at intermediate [α/Fe]. In agreement with previous results, we find that the high-α population is more prominent at smaller R, lower [Fe/H], and larger |z|, and that the sequence separation is smaller for Si and Ca than for Mg, O, and S. We find significant intrinsic scatter in [α/Fe] at fixed [Fe/H] for both the low-α and high-α populations, typically ∼0.04-dex. The means, dispersions, and relative amplitudes of this two-Gaussian description, and the dependence of these parameters on R, [Fe/H], and α-element, provide a quantitative target for chemical evolution models and a test for hydrodynamic simulations of disk galaxy formation. We argue that explaining the observed bimodality will probably require one or more sharp transitions in the disk’s gas accretion, star formation, or outflow history in addition to radial mixing of stellar populations.

Differentiation of Modernization Processes in EU Countries and in Poland in Time and Space - Non Classical View

The aim of this paper is a typology of EU-countries from the point of view of their modernization measures, a diagnostics and an evaluation of changes in a sectoral structure of the employment in EU-countries. Against this background there are exposed changes in Polish economy in the period 1997-2008. There were used the multidimensional comparative analysis of the sequence separation of homogenous objects subsets (cluster analysis and quick cluster) and the little known in Poland, but popular in the US, measurement technique of sectoral changes in time – the shift share-technique to illustrate and verify empirically the theory of three sectors by A. Fisher, C. Clark i J. Fourastiè, orientated to the evaluation of the modernization process of EU-economies.