Gerard Lemson

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We present the Millennium-II Simulation (MS-II), a very large N-body simulation of dark matter evolution in the concordance ΛCDM cosmology. The MS-II assumes the same cosmological parameters and uses the same particle number and output data structure as the original Millennium Simulation (MS), but was carried out in a periodic cube one-fifth the size (100 h(More)
We study the biasing relation between dark-matter halos or galaxies and the underlying mass distribution, using cosmological N-body simulations in which galaxies are modelled via semi-analytic recipes. The nonlinear, stochastic biasing is quantiied in terms of the mean biasing function and the scatter about it as a function of time, scale and object(More)
We present the first systematic study of (non-radio-selected) radio-loud narrow-line Seyfert 1 (NLS1) galaxies. Cross-correlation of the 'Catalogue of Quasars and Active Nuclei' with several radio and optical catalogues led to the identification of ∼11 radio-loud NLS1 candidates including 4 previously known ones. This study almost triples the number of(More)
We investigate trends between the recent star formation history and black hole growth in galaxy bulges in the Sloan Digital Sky Survey (SDSS). The galaxies lie at 0.01 < z < 0.07 where the fibre aperture covers only the central 0.6-4.0 kpc diameter of the galaxy. We find strong trends between black hole growth, as measured by dust-attenuation-corrected [O(More)
The formation of dark matter halos tends to occur anisotropically along the filaments of the Cosmic Web, which induces both ellipticity-ellipticity (EE) correlations between the shapes of halos, as well as ellipticity-direction (ED) cross-correlations between halo shapes and the directions to neighboring halos. We analyze the halo catalogue and the(More)
The field of e-science currently faces many challenges. Among the most important ones are the analysis of huge volumes of scientific data and the connection of various sciences and communities, thus enabling scientists to share scientific interests, data, and research results. These issues can be addressed by processing large data volumes on-thefly in the(More)
We present the online MultiDark Database – a Virtual Observatory-oriented, relational database for hosting various cosmological simulations. The data is accessible via an SQL (Structured Query Language) query interface, which also allows users to directly pose scientific questions, as shown in a number of examples in this paper. Further examples for the(More)
The Millennium Run is the largest simulation of the formation of structure within the ΛCDM cosmogony so far carried out. It uses 10 10 particles to follow the dark matter distribution in a cubic region 500h −1 Mpc on a side, and has a spatial resolution of 5 h −1 kpc. Application of simplified modelling techniques to the stored output of this calculation(More)