Collisional excitation of neutral hydrogen atoms can significantly increase the intensity of Balmer lines with respect to pure recombination. If this effect is not taken into account, the abundance analysis of these objects returns biased values, and the bias may be significant if accuracies better than a few percent are required. The most affected

Aims. We aimed at finding a physical explanation for the occurrence of macroturbulence in the atmospheres of hot massive stars, a phenomenon found in observations for more than a decade but that remains unexplained. Methods: We computed time series of line profiles for evolved massive stars broadened by rotation and by hundreds of low-amplitude

We use the OSUBSGS (Ohio State University Bright Spiral Galaxy Survey, Eskridge et al. 2002) and NIRS0S (Near-IR S0 Survey, Laurikainen et al. 2005) data to study the connection of bars and outer spiral structures. Using near-IR images, the non-axisymmetric gravity perturbation associated with the bar is evaluated at various distances outside the

We present a spectral analysis of a sample of red-sequence galaxies identified by van Dokkum as dry merger remnants and ongoing dry mergers. Kinematics, stellar population absorption features and ionization from emission lines are derived. We find that approximately half of the sample showing strong tidal features have younger stellar populations

We present first preliminary results from AKARI/FIS pointed observations of post-AGB stars and planetary nebulae (PNe). A first analysis of the radial (azimuthally averaged) profile of the observed sources shows no evidence for excess emission due to the presence of circumstellar dust. No (detached) circumstellar faint dust-shells are seen in the

We present AKARI/IRC observations of a sample of six extremely red IRAS sources, of which three are variable OH/IR stars and the rest are early post-AGB stars. The OH/IR stars show a red continuum with the expected strong 10 μm silicate absorption feature, while the post-AGB stars show an even redder continuum accompanied with a comparably weak