A scaling-relation for disc galaxies: circular-velocity gradient versus central surface brightness

Understand

For disc galaxies, a close relation exists between the distribution of light and the shape of the rotation curve.

• We quantify this relation by measuring the inner circular-velocity gradient d_{R}V(0) for spiral and irregular galaxies with high-quality rotation curves.
• We find that d_{R}V(0) correlates with the central surface brightness mu_{0} over more than two orders of magnitude in d_{R}V(0) and four orders of magnitudes in mu_{0}.
• This is a scaling-relation for disc galaxies.