Context: Local reductions of the stellar velocity dispersion in the central regions of galaxies are known as sigma-drops (σ-drops). Knowing the origin of these features can lead to better understanding of inner galactic dynamics. Aims: We present a sample of 20 σ-drop galaxies matched with a control sample of galaxies without σ-drop in order to

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We evaluate the nature of bulges in the Hubble sequence, based on an analysis of 216 disk galaxies of all morphological types (S0-Sd). For this purpose we collect our various analysis made separately for early and late-type galaxies, published in a series of papers. Using the criteria by Kormendy & Kennicutt we find strong evidence of pseudobulges

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The main goal of this work is to calculate the contributions of bound-bound transitions of helium to the cosmological recombination spectrum. We show that helium in the early Universe causes unique features to appear in the total cosmological recombination spectrum. These may provide a unique observational possibility to determine the relative