University of Ljubljana

About: University of Ljubljana is a education organization based out in Ljubljana, Slovenia. It is known for research contribution in the topics: Population & Liquid crystal. The organization has 17210 authors who have published 47013 publications receiving 1082684 citations. The organization is also known as: Univerza v Ljubljani.

The GALAH survey: observational overview and Gaia DR1 companion

Abstract: The Galactic Archaeology with HERMES (GALAH) Survey is a massive observational project to trace the Milky Way's history of star formation, chemical enrichment, stellar migration and minor mergers. Using high-resolution (R$\simeq$28,000) spectra taken with the High Efficiency and Resolution Multi-Element Spectrograph (HERMES) instrument at the Anglo-Australian Telescope (AAT), GALAH will determine stellar parameters and abundances of up to 29 elements for up to one million stars. Selecting targets from a colour-unbiased catalogue built from 2MASS, APASS and UCAC4 data, we expect to observe dwarfs at 0.3 to 3 kpc and giants at 1 to 10 kpc. This enables a thorough local chemical inventory of the Galactic thin and thick disks, and also captures smaller samples of the bulge and halo. In this paper we present the plan, process and progress as of early 2016 for GALAH survey observations. In our first two years of survey observing we have accumulated the largest high-quality spectroscopic data set at this resolution, over 200,000 stars. We also present the first public GALAH data catalogue: stellar parameters (Teff, log(g), [Fe/H], [alpha/Fe]), radial velocity, distance modulus and reddening for 10680 observations of 9860 Tycho-2 stars that may be included in the first Gaia data release.

Gaia Data Release 2. Properties and validation of the radial velocities

Abstract: Context. For Gaia DR2, 280 million spectra collected by the Radial Velocity Spectrometer instrument on board Gaia were processed, and median radial velocities were derived for 9.8 million sources brighter than G RVS = 12 mag.Aims. This paper describes the validation and properties of the median radial velocities published in Gaia DR2.Methods. Quality tests and filters were applied to select those of the 9.8 million radial velocities that have the quality to be published in Gaia DR2. The accuracy of the selected sample was assessed with respect to ground-based catalogues. Its precision was estimated using both ground-based catalogues and the distribution of the Gaia radial velocity uncertainties. Results. Gaia DR2 contains median radial velocities for 7 224 631 stars, with T eff in the range [3550, 6900] K, which successfully passed the quality tests. The published median radial velocities provide a full-sky coverage and are complete with respect to the astrometric data to within 77.2% (for G ≤ 12.5 mag). The median radial velocity residuals with respect to the ground-based surveys vary from one catalogue to another, but do not exceed a few 100 m s−1 . In addition, the Gaia radial velocities show a positive trend as a function of magnitude, which starts around G RVS ~ 9 mag and reaches about + 500 m s−1 at G RVS = 11.75 mag. The origin of the trend is under investigation, with the aim to correct for it in Gaia DR3. The overall precision, estimated from the median of the Gaia radial velocity uncertainties, is 1.05 km s−1 . The radial velocity precision is a function of many parameters, in particular, the magnitude and effective temperature. For bright stars, G RVS ∈ [4, 8] mag, the precision, estimated using the full dataset, is in the range 220–350 m s−1 , which is about three to five times more precise than the pre-launch specification of 1 km s−1 . At the faint end, G RVS = 11.75 mag, the precisions for T eff = 5000 and 6500 K are 1.4 and 3.7 km s−1 , respectively.

Understanding Knowledge Hiding in Organizations

Abstract: J Organ Behav. 2019;40:779–782. Summary In our introduction to this special issue on understanding knowledge hiding in organizations, we provide some context to how andwhy this phenomenon should be studied. We then describe the five articles that comprise the special issue, and we note some common themes and divergences in this collection. Our introduction concludes with some suggestions for future research on knowledge hiding in organizations.