Unveiling the rarest morphologies of the LOFAR Two-metre Sky Survey radio source population with self-organised maps

Context. The Low Frequency Array (LOFAR) Two-metre Sky Survey (LoTSS) is a low-frequency radio continuum survey of the Northern sky at an unparalleled resolution and sensitivity. Aims. In order to fully exploit this huge dataset and those produced by the Square Kilometre Array in the next decade, automated methods in machine learning and data-mining will be increasingly essential both for morphological classifications and for identifying optical counterparts to the radio sources. Methods. Using self-organising maps (SOMs), a form of unsupervised machine learning, we created a dimensionality reduction of the radio morphologies for the ∼25k extended radio continuum sources in the LoTSS first data release, which is only ∼2 percent of the final LoTSS survey. We made use of PINK, a code which extends the SOM algorithm with rotation and flipping invariance, increasing its suitability and effectiveness for training on astronomical sources. Results. After training, the SOMs can be used for a wide range of science exploitation and we present an illustration of their potential by finding an arbitrary number of morphologically rare sources in our training data (424 square degrees) and subsequently in an area of the sky (∼5300 square degrees) outside the training data. Objects found in this way span a wide range of morphological and physical categories: extended jets of radio active galactic nuclei, diffuse cluster haloes and relics, and nearby spiral galaxies. Finally, to enable accessible, interactive, and intuitive data exploration, we showcase the LOFAR-PyBDSF Visualisation Tool, which allows users to explore the LoTSS dataset through the trained SOMs

Simulation und Optimierung von III/V-Halbleiterbauelementen Abschlussbericht

The modeling and simulation of semiconductor devices is done mainly on the base of the well known macroscopic semiconductor equations. More accurate results are possible by including of microscopic effects (Quantum and particle models). These simulation methods require a considerable computational expense. The target of the project was the extension of present simulation programs for the two- and three-dimensional numerical analysis of semiconductor devices to simulate novel III/V-semiconductor devices with sufficient accuracy. Therefore a simulation algorithm for a coupled microscopic/macroscopic simulation was created (Solution of Schroedinger equation, consideration of tunneling processes). Furthermore extensive calculations and optimizations of novel III/V-semiconductor devices were carried out. The results are requirements for the future simulation of nanoelectronic devices. (orig.)SIGLEAvailable from TIB Hannover: F96B1381+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Radio Galaxy Zoo: host galaxies and radio morphologies derived from visual inspection

ISSN:0035-8711ISSN:1365-2966ISSN:1365-871