On the relation between circular velocity and central velocity dispersion in high and low surface brightness galaxies
Abstract
In order to investigate the correlation between the circular velocity Vc and the central velocity dispersion of the spheroidal component sigmac, we analyzed these quantities for a sample of 40 high surface brightness disc galaxies (hereafter HSB), 8 giant low surface brightness spiral galaxies (hereafter LSB), and 24 elliptical galaxies characterized by flat rotation curves. We find that the Vc-sigmac relation is descri ed by a linear law out to velocity dispersions as low as sigmac~50km/s, while in previous works a power law was adopted for galaxies with sigmac>80k/ms. Elliptical galaxies with Vc based on dynamical models or directly derived from the HI rotation curves follow the same relation as the HSB galaxies in the Vc-sigmac plane. On the contrary, the LSB galaxies follow a different relation, since most of them show either higher Vc (or lower sigmac) with respect to the HSB galaxies. This argues against the relevance of baryon collapse in the radial density profile of the dark matter haloes of LSB galaxies. (abridged)
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