The volumetric star formation law in nearby galaxies

Understand

Star formation laws are empirical relations between the cold gas (HI+H$_2$) content of a galaxy and its star formation rate (SFR), being crucial for any model of galaxy formation and evolution.

• A well known example of such laws is the Schmidt-Kennicutt law, which is based on the projected surface densities.
• However, it has been long unclear whether a more fundamental relation exists between the intrinsic volume densities.
• By assuming the vertical hydrostatic equilibrium, we infer radial profiles for the thickness of gaseous discs in a sample of 23 local galaxies, and use these measurements to convert the observed surface densities of the gas and the SFR into the de-projected volume densities.