Environmental effects on galaxy luminosity functions: the cluster Abell 496

We have derived the galaxy luminosity function in various regions of the cluster of galaxies Abell 496 from a wide field image in the I band. A Schechter function fit in the 17≤ I_AB ≤22(–19.5≤ M_IAB ≤ –14.5) magnitude interval gives a steep power law index, which is somewhat steeper in the outer regions than in the inner zones. This result agrees with previous findings obtained by several teams on the Coma cluster and can be interpreted as due to the fact that faint galaxies are accreted by large ones in the central regions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Seismic behaviour of timber-laced stone masonry buildings before and after interventions: shaking table tests on a two-storey masonry model

The present work focuses on the seismic behaviour of timber-laced masonry buildings with timber floors, before and after the application of intervention techniques. A two-storey building with timber ties (scale 1:2) was subjected to biaxial seismic actions. Prior to the execution of shaking table tests, the dynamic characteristics of the model were identified. The base acceleration was increased step-wise until the occurrence of significant but repairable damages. Afterwards, the masonry was strengthened by means of grouting, whereas the diaphragm action of the top floor of the building was enhanced and the model was re-tested. The tests on the timber reinforced model before strengthening show that the presence of timber ties within the masonry elements contributes to improved seismic behaviour. The performance of the model after strengthening shows that the selected intervention techniques led to a significant improvement of the seismic behaviour of the building model.     

A Virgo high-resolution Hα kinematical survey – II. The Atlas

A catalogue of ionized gas velocity fields for a sample of 30 spiral and irregular galaxies of the Virgo cluster has been obtained by using 3D optical data. The aim of this survey is to study the influence of high-density environments on the gaseous kinematics of local cluster galaxies. Observations of the Hα line by means of Fabry–Perot interferometry have been performed at the Canada–France–Hawaii Telescope, European Southern Observatory 3.6-m telescope, Observatoire de Haute-Provence 1.93-m telescope and Observatoire du mont Mégantic telescope at angular and spectral samplings from 0.4 to 1.6 arcsec and 7 to 16 km s⁻¹. A recently developed, automatic and adaptive spatial binning technique is used to reach a nearly constant signal-to-noise ratio (S/N) over the whole field of view, allowing us to keep a high spatial resolution in high-S/N regions and extend the detection of signal in low-S/N regions. This paper is part of a series and presents the integrated emission-line and velocity maps of the galaxies. Both Hα morphologies and kinematics exhibit signs of perturbations in the form of, for example, external filaments, inner and nuclear spiral- and ring-like structures, inner kinematical twists, kinematical decoupling of a nuclear spiral, streaming motions along spiral arms and misalignment between kinematical and photometric orientation axes.