Tracing the relation between black holes and dark haloes

We present new velocity dispersion measurements for a set of 12 spiral galaxies and use them to derive a more accurate V_c - sigma relation which holds for a wide morphological range of galaxies. Combined with the M_BH - sigma relation, this relation can be used as a tool to estimate supermassive black hole (SMBH) masses by means of the asymptotic circular velocity. Together with the Tully-Fisher relation, it serves as a constraint for galaxy formation and evolution models.Comment: 2 pages, 2 figures, to appear in Proc. IAU Symp. 220, "Dark Matter in Galaxies" eds. S. Ryder, D.J. Pisano, M. Walker, & K. Freeman (San Francisco: ASP

FCC046: a candidate gaseous polar ring dwarf elliptical galaxy in the Fornax Cluster

FCC046 is a Fornax Cluster dwarf elliptical galaxy. Optical observations have shown that this galaxy, besides an old and metal-poor stellar population, also contains a very young centrally concentrated population and is actively forming stars, albeit at a very low level. Here, we report on 21cm observations of FCC046 with the Australia Telescope Compact Array (ATCA) which we conducted in the course of a small survey of Fornax Cluster early-type dwarf galaxies. We have discovered a ~10^7 Mo HI cloud surrounding FCC046. We show that the presence of this significant gas reservoir offers a concise explanation for this galaxy's optical morphological and kinematical properties. Surprisingly, the HI gas, as evidenced by its morphology and its rotational motion around the galaxy's optical major axis, is kinematically decoupled from the galaxy's stellar body. This is the first time such a ring of gaseous material in minor-axis rotation is discovered around a dwarf galaxy.Comment: 5 pages, 4 figures, published in Astrophysical Journal Letter

Automated UML-based ontology generation in OSLO²

In 2015, Flanders Information started the OSLO2 project, aimed at easing the exchange of data and increasing the interoperability of Belgian government services. RDF ontologies were developed to break apart the government data silos and stimulate data reuse. However, ontology design still encounters a number of difficulties. Since domain experts are generally unfamiliar with RDF, a design process is needed that allows these experts to efficiently contribute to intermediate ontology prototypes. We designed the OSLO2 ontologies using UML, a modeling language well known within the government, as a single source specification. From this source, the ontology and other relevant documents are generated. This paper describes the conversion tooling and the pragmatic approaches that were taken into account in its design. While this tooling is somewhat focused on the design principles used in the OSLO2 project, it can serve as the basis for a generic conversion tool. All source code and documentation are available online

Observational evidence for a connection between SMBHs and dark matter haloes

We investigate the relation between circular velocity vc and bulge velocity dispersion sigma in spiral galaxies, based on literature data and new spectroscopic observations. We find a strong, nearly linear vc-sigma correlation with a negligible intrinsic scatter, and a striking agreement with the corresponding relation for elliptical galaxies. The least massive galaxies (sigma < 80 km/s) significantly deviate from this relation. We combine this vc-sigma correlation with the well-known MBH-sigma relation to obtain a tight correlation between circular velocity and supermassive black hole mass, and interpret this as observational evidence for a close link between supermassive black holes and the dark matter haloes in which they presumably formed. Apart from being an important ingredient for theoretical models of galaxy formation and evolution, the relation between MBH and circular velocity has the potential to become an important practical tool in estimating supermassive black hole masses in spiral galaxies.Comment: 4 pages, 1 figure, to appear in "The Interplay among Black Holes, Stars and ISM in Galactic Nuclei", IAU Symposium 222, eds. Th. Storchi Bergmann, L.C. Ho & H.R. Schmit

Completely analytical families of anisotropic gamma-models

We present new analytical distribution functions for anisotropic spherical galaxies. They have the density profiles of the gamma-models, which allow a wide range of central density slopes, and are widely used to fit elliptical galaxies and the bulges of spiral galaxies. Most of our models belong to two two-parameter families. One of these parameters is the slope gamma of the central density cusp. The other allows a wide range of varying radial and tangential anisotropies, at either small or large radii. We give analytical formulas for their distribution functions, velocity dispersions, and the manner in which energy and transverse velocity are distributed between orbits. We also give some of their observable properties, including line-of-sight velocity profiles which have been computed numerically. Our models can be used to provide a useful tool for creating initial conditions for N-body and Monte Carlo simulations.Comment: 21 pages, 15 figures, accepted for publication in MNRA

Dynamical models linking BH masses and DM content

We investigate the relation between the dark matter distribution of galaxies and their central supermassive black holes which is suggested by the v_c-sigma relation. Since early-type galaxies appear to have larger black holes than late-type ones, we look for an equivalent pattern in the dark matter distribution as a function of Hubble type. To achieve our goal we use a state-of-the-art modelling code that allows a variety of geometries to be fitted to a combination of radio and optical observations of galaxies with different morphology.Comment: 2 pages, 2 figures, contributed paper to Proceedings of the Conference "Growing Black Holes" held in Garching, Germany, June 21-25, 2004, edited by A. Merloni, S. Nayakshin and R. Sunyaev, Springer-Verlag series of "ESO Astrophysics Symposia

'Internationale stijl' in Mechelen: ontdekking, conservatie en onderzoek van de muurschilderingen van rond 1400 in de toren van de Sint-Janskerk

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Les Mollusques perforants

In search of a better protection against predators, molluscs have developped various ways of adaptation and evolution to bury themselves in different substrates. The most striking exemples are found among the bivalvia

Grotesken uit de Italiaanse renaissance. Onderzoek en restauratie van de muur- en gewelfschilderingen(1537) van de Onze-Lieve-Vrouw-Lofkapel in de Antwerpse kathedraal (prov. Antwerpen)

De conservatie en restauratie van de schilderingen (1537) van de Onze-Lieve-Vrouw-Lofkapel vormden de aanleiding tot verder onderzoek naar de context van hun ontstaan en geschiedenis, de filosofie en deontologie van de huidige restauratiebehandeling vooral met betrekking tot de re-integratie van lacunes, de gebruikte materialen en technieken van de oude schildering, de iconografie en de herkomst van de motieven, de identificatie van de heraldische voorstellingen en last but not least de persoon van de schilder