Velocity and magnetic fields are derived from subtracting intensity measurements made at different times and, normally, under different conditions. This differential imaging property puts important requirements on image stabilization. Examples of the implications for the Solar Orbiter mission are discussed. Similarly, we review how spectral and

A detailed imaging analysis of the globular cluster (GC) system of the Sombrero galaxy (NGC 4594) has been accomplished using a six-image mosaic from the Hubble Space Telescope Advanced Camera for Surveys. The quality of the data is such that contamination by foreground stars and background galaxies is negligible for all but the faintest 5% of the

The galaxy group Klemola 13 is composed of at least seven independent members including the starburst galaxy Tol 9. Our analysis using optical/NIR and Ha imaging together with optical spectroscopy suggests that it is interacting with some members of the group. We propose H I observations of Klemola 13 in order to map the distribution and kinematics

Context: .Satellite accretion events have been invoked for mimicking the internal secular evolutionary processes of bulge growth. However, N-body simulations of satellite accretions have paid little attention to the evolution of bulge photometric parameters, to the processes driving this evolution, and to the consistency of this evolution with

Context: .Shells in Elliptical Galaxies are faint, sharp-edged features, believed to provide evidence of a recent (˜ 0.5 - 2 × 109 years ago) merger event. We analyse the Globular Cluster (GC) systems of six shell elliptical galaxies, to examine the effects of mergers upon the GC formation history. Aims: .We examine the colour distributions, and

Aims.We study fast magnetohydrodynamic waves in a system of two coronal loops modeled as smoothed, dense plasma slabs in a uniform magnetic field. This allows us to analyse in a simple configuration the collective behaviour of the structure due to the interaction between the slabs. Methods: .We first calculate the normal modes of the system and