In spiral galaxies, the formation of new stars is regulated by a law involving the star-formation rate (SFR) per unit area, the gas surface density, and the galaxy orbital time (Kennicutt 1998). This has been commonly interpreted as the effect of spiral arms triggering star formation. In Lelli et al. 2014, we find that dwarf galaxies follow a similar law despite they lack spiral arms. We also find that the SFR surface density correlates with the inner steepness of the galaxy rotation curve (circular-velocity gradient), pointing to a close link between the star-formation activity and the galaxy gravitational potential (distribution of baryons and dark matter).
